March 6, 2013

Publications

Group members please use this affiliation for your publications:
Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, USA


Google Scholar Link: http://scholar.google.com/citations?user=LbYsy_QAAAAJ&hl=en


2018

  • [PDF] [URL] J. Corea, P. Ye, D. Seo, K. Butts-Pauly, A. C. Arias, and M. Lustig, “Printed Receive Coils with High Acoustic Transparency for Magnetic Resonance Guided Focused Ultrasound,” Scientific Reports, vol. 8, iss. 3392, 2018.

    [Abstract]

    In magnetic resonance guided focused ultrasound (MRgFUS) therapy sound waves are focused through the body to selectively ablate difficult to access lesions and tissues. A magnetic resonance imaging (MRI) scanner non-invasively tracks the temperature increase throughout the tissue to guide the therapy. In clinical MRI, tightly fitted hardware comprised of multichannel coil arrays are required to capture high quality images at high spatiotemporal resolution. Ablating tissue requires a clear path for acoustic energy to travel but current array materials scatter and attenuate acoustic energy. As a result coil arrays are placed outside of the transducer, clear of the beam path, compromising imaging speed, resolution, and temperature accuracy of the scan. Here we show that when coil arrays are fabricated by additive manufacturing (i.e., printing), they exhibit acoustic transparency as high as 89.5%. This allows the coils to be placed in the beam path increasing the image signal to noise ratio (SNR) five-fold in phantoms and volunteers. We also characterize printed coil materials properties over time when submerged in the water required for acoustic coupling. These arrays offer high SNR and acceleration capabilities, which can address current challenges in treating head and abdominal tumors allowing MRgFUS to give patients better outcomes.

    [Bibtex]

    @article {Corea2018AcousticTransparency,
    author = {Corea, Joseph and Ye, Patrick and Seo, Dongjin and Butts-Pauly, Kim and Arias, Ana C. and Lustig, Michael},
    title = {Printed Receive Coils with High Acoustic Transparency for Magnetic Resonance Guided Focused Ultrasound},
    journal = {Scientific Reports},
    volume = {8},
    number = {3392},
    year = {2018},
    month = {Feb},
    day = {21},
    doi = {10.1038/s41598-018-21687-1},
    publisher={Nature Publishing Group}, abstract = {In magnetic resonance guided focused ultrasound (MRgFUS) therapy sound waves are focused through the body to selectively ablate difficult to access lesions and tissues. A magnetic resonance imaging (MRI) scanner non-invasively tracks the temperature increase throughout the tissue to guide the therapy. In clinical MRI, tightly fitted hardware comprised of multichannel coil arrays are required to capture high quality images at high spatiotemporal resolution. Ablating tissue requires a clear path for acoustic energy to travel but current array materials scatter and attenuate acoustic energy. As a result coil arrays are placed outside of the transducer, clear of the beam path, compromising imaging speed, resolution, and temperature accuracy of the scan. Here we show that when coil arrays are fabricated by additive manufacturing (i.e., printing), they exhibit acoustic transparency as high as 89.5%. This allows the coils to be placed in the beam path increasing the image signal to noise ratio (SNR) five-fold in phantoms and volunteers. We also characterize printed coil materials properties over time when submerged in the water required for acoustic coupling. These arrays offer high SNR and acceleration capabilities, which can address current challenges in treating head and abdominal tumors allowing MRgFUS to give patients better outcomes.},
    URL = {https://www.nature.com/articles/s41598-018-21687-1},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/Corea2018AcousticTransparency.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/Corea2018AcousticTransparency.pdf}
    }
  • [PDF] [URL] I. Deckman, B. P. Lechene, A. Pierre, and A. C. Arias, “All-printed full-color pixel organic photodiode array with a single active layer,” Organic Electronics, vol. 56, pp. 139-145, 2018.

    [Abstract]

    A new fabrication method to realize fully-printed organic photodiode (OPD) arrays capable of RGB light separation is presented. From the photocurrents generated by each pixel type under the light from RGB LEDs, we demonstrate that this “White”, “Yellow” and “Red” array can successfully detect and reconstruct colors in the RGB system, with an average accuracy of 98.5%. A flexible broadband OPD array is printed on PEN substrate by blade-coating PEDOT:PSS, a polyethylenimine cathode interlayer and the photo-active layer, and screen-printing on top a patterned PEDOT:PSS anode. The OPD array achieves an average EQE of ∼37% at −4 V bias over the whole visible spectrum, 5 orders of magnitude of linear dynamic range (LDR), a 0.5 nA/cm2 dark current, and maintains these performances in ambient conditions for more than 30 h. Pixels detecting “White”, “Yellow” and “Red” are fabricated by spray-coating two color filters. The substrate is used as a separator between the filters and OPD array. This physical separation allows solution processing of the filters regardless of their electrical properties or of the compatibility of their solvents with the OPD, thus broadening the choice of filter materials while offering a simple fabrication process. The combination of broadband OPD and broadband filters used in this configuration can significantly simplify the fabrication of spectrally-selective photosensors and full-color imagers.

    [Bibtex]

    @article {Igal2018fullcolorpixel,
    author = {Deckman, Igal and Lechene, P. Balthazar and Pierre, Adrien and Arias, Ana C.},
    title = {All-printed full-color pixel organic photodiode array with a single active layer},
    journal = {Organic Electronics},
    volume = {56},
    pages = {139–145},
    year = {2018},
    doi = {10.1016/j.orgel.2018.02.009},
    abstract = {A new fabrication method to realize fully-printed organic photodiode (OPD) arrays capable of RGB light separation is presented. From the photocurrents generated by each pixel type under the light from RGB LEDs, we demonstrate that this “White”, “Yellow” and “Red” array can successfully detect and reconstruct colors in the RGB system, with an average accuracy of 98.5%. A flexible broadband OPD array is printed on PEN substrate by blade-coating PEDOT:PSS, a polyethylenimine cathode interlayer and the photo-active layer, and screen-printing on top a patterned PEDOT:PSS anode. The OPD array achieves an average EQE of ∼37% at −4 V bias over the whole visible spectrum, 5 orders of magnitude of linear dynamic range (LDR), a 0.5 nA/cm2 dark current, and maintains these performances in ambient conditions for more than 30 h. Pixels detecting “White”, “Yellow” and “Red” are fabricated by spray-coating two color filters. The substrate is used as a separator between the filters and OPD array. This physical separation allows solution processing of the filters regardless of their electrical properties or of the compatibility of their solvents with the OPD, thus broadening the choice of filter materials while offering a simple fabrication process. The combination of broadband OPD and broadband filters used in this configuration can significantly simplify the fabrication of spectrally-selective photosensors and full-color imagers.},
    URL = {https://www.sciencedirect.com/science/article/pii/S156611991830051X},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/Igal2018fullcolorpixel.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/Igal2018fullcolorpixel.pdf}
    }

2017

  • [PDF] [URL] B. P. Lechene, R. Clerc, and A. C. Arias, “Theoretical analysis and characterization of the energy conversion and storage efficiency of photo-supercapacitors,” Solar Energy Materials and Solar Cells, vol. 172, pp. 202-212, 2017.

    [Abstract]

    The time-dependent dynamics of the charge and discharge of photo-supercapacitors (PSC), devices which combine a supercapacitor with a solar cell, are investigated using a semi-analytical model. For a given PSC, it is found that the maximum Energy Conversion and Storage Efficiency (ECSE) is a direct function of the Power Conversion Efficiency (PCE) and Fill Factor (FF) of the solar cell. The capacitance, series and shunt resistances of the supercapacitor affect the time constants of the PSC and the value of the maximum ECSE. To experimentally measure the maximum value of ECSE with at most 2 charge-discharge cycles, a simple experimental procedure is proposed, which consists in comparing the power flowing through the supercapacitor and the energy already stored in it. The theoretical results are validated with experiments on a PSC made from an organic solar cell and a commercial supercapacitor.

    [Bibtex]

    @article {Balthazar2017photosupercapacitors,
    author = {Lechene, P. Balthazar and Clerc, Raphael and Arias, Ana C.},
    title = {Theoretical analysis and characterization of the energy conversion and
    storage efficiency of photo-supercapacitors},
    journal = {Solar Energy Materials and Solar Cells},
    volume = {172},
    pages = {202–212},
    year = {2017},
    doi = {10.1016/j.solmat.2017.07.034},
    abstract = {The time-dependent dynamics of the charge and discharge of photo-supercapacitors (PSC), devices which combine a supercapacitor with a solar cell, are investigated using a semi-analytical model. For a given PSC, it is found that the maximum Energy Conversion and Storage Efficiency (ECSE) is a direct function of the Power Conversion Efficiency (PCE) and Fill Factor (FF) of the solar cell. The capacitance, series and shunt resistances of the supercapacitor affect the time constants of the PSC and the value of the maximum ECSE. To experimentally measure the maximum value of ECSE with at most 2 charge-discharge cycles, a simple experimental procedure is proposed, which consists in comparing the power flowing through the supercapacitor and the energy already
    stored in it. The theoretical results are validated with experiments on a PSC made from an organic solar cell and a commercial supercapacitor.},
    URL = {https://www.sciencedirect.com/science/article/pii/S0927024817304282},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/Balthazar2017photosupercapacitors.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/Balthazar2017photosupercapacitors.pdf}
    }
  • [PDF] [URL] A. M. Zamarayeva, A. E. Ostfeld, M. Wang, J. K. Duey, I. Deckman, B. P. Lechêne, G. Davies, D. A. Steingart, and A. C. Arias, “Flexible and stretchable power sources for wearable electronics,” Science Advances, vol. 3, iss. 6, 2017.

    [Abstract]

    Flexible and stretchable power sources represent a key technology for the realization of wearable electronics. Developing flexible and stretchable batteries with mechanical endurance that is on par with commercial standards and offer compliance while retaining safety remains a significant challenge. We present a unique approach that demonstrates mechanically robust, intrinsically safe silver-zinc batteries. This approach uses current collectors with enhanced mechanical design, such as helical springs and serpentines, as a structural support and backbone for all battery components. We show wire-shaped batteries based on helical band springs that are resilient to fatigue and retain electrochemical performance over 17,000 flexure cycles at a 0.5-cm bending radius. Serpentine-shaped batteries can be stretched with tunable degree and directionality while maintaining their specific capacity. Finally, the batteries are integrated, as a wearable device, with a photovoltaic module that enables recharging of the batteries.

    [Bibtex]

    @article {zamarayeva2017flexible,
    author = {Zamarayeva, Alla M. and Ostfeld, Aminy E. and Wang, Michael and Duey, Jerica K. and Deckman, Igal and Lech{\^e}ne, Balthazar P. and Davies, Greg and Steingart, Daniel A. and Arias, Ana Claudia},
    title = {Flexible and stretchable power sources for wearable electronics},
    volume = {3},
    number = {6},
    year = {2017},
    doi = {10.1126/sciadv.1602051},
    publisher = {American Association for the Advancement of Science},
    abstract = {Flexible and stretchable power sources represent a key technology for the realization of wearable electronics. Developing flexible and stretchable batteries with mechanical endurance that is on par with commercial standards and offer compliance while retaining safety remains a significant challenge. We present a unique approach that demonstrates mechanically robust, intrinsically safe silver-zinc batteries. This approach uses current collectors with enhanced mechanical design, such as helical springs and serpentines, as a structural support and backbone for all battery components. We show wire-shaped batteries based on helical band springs that are resilient to fatigue and retain electrochemical performance over 17,000 flexure cycles at a 0.5-cm bending radius. Serpentine-shaped batteries can be stretched with tunable degree and directionality while maintaining their specific capacity. Finally, the batteries are integrated, as a wearable device, with a photovoltaic module that enables recharging of the batteries.},
    URL = {http://advances.sciencemag.org/content/3/6/e1602051},
    eprint = {http://advances.sciencemag.org/content/3/6/e1602051.full.pdf},
    journal = {Science Advances},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/zamarayeva2017flexible.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/zamarayeva2017flexible.pdf}
    }
  • [PDF] [URL] D. Han, Y. Khan, J. Ting, S. M. King, N. Yaacobi-Gross, M. J. Humphries, C. J. Newsome, and A. C. Arias, “Flexible Blade-Coated Multicolor Polymer Light-Emitting Diodes for Optoelectronic Sensors,” Advanced Materials, p. 1606206–n/a, 2017.
    1606206
    [Abstract]
    A method to print two materials of different functionality during the same printing step is presented. In printed electronics, devices are built layer by layer and conventionally only one type of material is deposited in one pass. Here, the challenges involving printing of two emissive materials to form polymer light-emitting diodes (PLEDs) that emit light of different wavelengths without any significant changes in the device characteristics are described. The surface-energy-patterning technique is utilized to print materials in regions of interest. This technique proves beneficial in reducing the amount of ink used during blade coating and improving the reproducibility of printed films. A variety of colors (green, red, and near-infrared) are demonstrated and characterized. This is the first known attempt to print multiple materials by blade coating. These devices are further used in conjunction with a commercially available photodiode to perform blood oxygenation measurements on the wrist, where common accessories are worn. Prior to actual application, the threshold conditions for each color are discussed, in order to acquire a stable and reproducible photoplethysmogram (PPG) signal. Finally, based on the conditions, retrieved PPG and oxygenation measurements are successfully performed on the wrist with green and red PLEDs.

    [Bibtex]

    @article {han2017flexible,
    author = {Han, Donggeon and Khan, Yasser and Ting, Jonathan and King, Simon M. and Yaacobi-Gross, Nir and Humphries, Martin J. and Newsome, Christopher J. and Arias, Ana C.},
    title = {Flexible Blade-Coated Multicolor Polymer Light-Emitting Diodes for Optoelectronic Sensors},
    journal = {Advanced Materials},
    issn = {1521-4095},
    url = {http://dx.doi.org/10.1002/adma.201606206},
    doi = {10.1002/adma.201606206},
    pages = {1606206–n/a},
    keywords = {blade coating, flexible electronics, polymer light-emitting diodes (PLEDs), printed sensors, pulse oximetry, organic light-emitting diodes (OLEDs), wearable sensors},
    year = {2017},
    note = {1606206},
    abstract = {A method to print two materials of different functionality during the same printing step is presented. In printed electronics, devices are built layer by layer and conventionally only one type of material is deposited in one pass. Here, the challenges involving printing of two emissive materials to form polymer light-emitting diodes (PLEDs) that emit light of different wavelengths without any significant changes in the device characteristics are described. The surface-energy-patterning technique is utilized to print materials in regions of interest. This technique proves beneficial in reducing the amount of ink used during blade coating and improving the reproducibility of printed films. A variety of colors (green, red, and near-infrared) are demonstrated and characterized. This is the first known attempt to print multiple materials by blade coating. These devices are further used in conjunction with a commercially available photodiode to perform blood oxygenation measurements on the wrist, where common accessories are worn. Prior to actual application, the threshold conditions for each color are discussed, in order to acquire a stable and reproducible photoplethysmogram (PPG) signal. Finally, based on the conditions, retrieved PPG and oxygenation measurements are successfully performed on the wrist with green and red PLEDs.},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/han2017flexible.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/han2017flexible.pdf}
    }
  • [PDF] A. E. Ostfeld and A. C. Arias, “Flexible photovoltaic power systems: integration opportunities, challenges and advances,” Flexible and Printed Electronics, vol. 2, iss. 1, p. 13001, 2017.

    [Abstract]

    Photovoltaic power systems, consisting of solar modules, energy storage, and power management electronics, are of great importance for applications ranging from off-grid and portable power to ambient light harvesting for sensor nodes. Co-design and integration of the components using printing and coating methods on flexible substrates enable the production of effective and customizable systems for these diverse applications. In this article, we review photovoltaic module and energy storage technologies suitable for integration into flexible power systems. We discuss the design of electrical characteristics for these systems that enable them to power desired loads efficiently, as well as strategies for physically combining the components. Functions and design considerations of power management electronics are presented along with recent progress toward printed and flexible power electronics. We analyze both hybrid and fully flexible photovoltaic systems and the critical role of the application in the choices of materials and architectures for the system components.

    [Bibtex]

    @article{ostfeld2017flexible,
    author={Aminy E Ostfeld and Ana Claudia Arias},
    title={Flexible photovoltaic power systems: integration opportunities, challenges and advances},
    journal={Flexible and Printed Electronics},
    volume={2},
    number={1},
    pages={013001},
    url={http://stacks.iop.org/2058-8585/2/i=1/a=013001},
    year={2017},
    abstract={Photovoltaic power systems, consisting of solar modules, energy storage, and power management electronics, are of great importance for applications ranging from off-grid and portable power to ambient light harvesting for sensor nodes. Co-design and integration of the components using printing and coating methods on flexible substrates enable the production of effective and customizable systems for these diverse applications. In this article, we review photovoltaic module and energy storage technologies suitable for integration into flexible power systems. We discuss the design of electrical characteristics for these systems that enable them to power desired loads efficiently, as well as strategies for physically combining the components. Functions and design considerations of power management electronics are presented along with recent progress toward printed and flexible power electronics. We analyze both hybrid and fully flexible photovoltaic systems and the critical role of the application in the choices of materials and architectures for the system components.},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/ostfeld2017flexible.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/ostfeld2017flexible.pdf}
    }
  • [PDF] A. Pierre, A. Gaikwad, and A. C. Arias, “Charge-integrating organic heterojunction phototransistors for wide-dynamic-range image sensors,” Nature Photonics, 2017.
    Article
    [Abstract]
    Solution-processed phototransistors can substantially advance the performance of image sensors. Phototransistors exhibit large photoconductive gain and a sublinear responsivity to irradiance, which enables a logarithmic sensing of irradiance that is akin to the human eye and has a wider dynamic range than photodiode-based image sensors. Here, we present a novel solution-processed phototransistor composed of a heterostructure between a high-mobility organic semiconductor and an organic bulk heterojunction. The device efficiently integrates photogenerated charge during the period of a video frame then quickly discharges it, which significantly increases the signal-to-noise ratio compared with sampling photocurrent during readout. Phototransistor-based image sensors processed without photolithography on plastic substrates integrate charge with external quantum efficiencies above 100\% at 100 frames per second. In addition, the sublinear responsivity to irradiance of these devices enables a wide dynamic range of 103 dB at 30 frames per second, which is competitive with state-of-the-art image sensors.

    [Bibtex]

    @Article{pierre2017charge,
    author={Pierre, Adrien and Gaikwad, Abhinav and Arias, Ana Claudia},
    title={Charge-integrating organic heterojunction phototransistors for wide-dynamic-range image sensors},
    journal={Nature Photonics},
    year={2017},
    month={Feb},
    day={20},
    publisher={Nature Publishing Group},
    abstract={Solution-processed phototransistors can substantially advance the performance of image sensors. Phototransistors exhibit large photoconductive gain and a sublinear responsivity to irradiance, which enables a logarithmic sensing of irradiance that is akin to the human eye and has a wider dynamic range than photodiode-based image sensors. Here, we present a novel solution-processed phototransistor composed of a heterostructure between a high-mobility organic semiconductor and an organic bulk heterojunction. The device efficiently integrates photogenerated charge during the period of a video frame then quickly discharges it, which significantly increases the signal-to-noise ratio compared with sampling photocurrent during readout. Phototransistor-based image sensors processed without photolithography on plastic substrates integrate charge with external quantum efficiencies above 100\% at 100 frames per second. In addition, the sublinear responsivity to irradiance of these devices enables a wide dynamic range of 103 dB at 30 frames per second, which is competitive with state-of-the-art image sensors.},
    note={Article},
    issn={1749-4893},
    url={http://dx.doi.org/10.1038/nphoton.2017.15},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/pierre2017charge.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/pierre2017charge.pdf}
    }
  • [PDF] [URL] A. M. Gaikwad and A. C. Arias, “Understanding the Effects of Electrode Formulation on the Mechanical Strength of Composite Electrodes for Flexible Batteries,” ACS Applied Materials & Interfaces, p. null, 2017.
    PMID: 28151639
    [Abstract]
    Flexible lithium-ion batteries are necessary for powering the next generation of wearable electronic devices. In most designs, the mechanical flexibility of the battery is improved by reducing the thickness of the active layers, which in turn reduces the areal capacity and energy density of the battery. The performance of a battery depends on the electrode composition, and in most flexible batteries, standard electrode formulation is used, which is not suitable for flexing. Even with considerable efforts made toward the development of flexible lithium-ion batteries, the formulation of the electrodes has received very little attention. In this study, we investigate the relation between the electrode formulation and the mechanical strength of the electrodes. Peel and drag tests are used to compare the adhesion and cohesion strength of the electrodes. The strength of an electrode is sensitive to the particle size and the choice of polymeric binder. By optimizing the electrode composition, we were able to fabricate a high areal capacity (∼2 mAh/cm2) flexible lithium-ion battery with conventional metal-based current collectors that shows superior electrochemical and mechanical performance in comparison to that of batteries with standard composition.

    [Bibtex]

    @article{abhinav2017understanding,
    author = {Gaikwad, Abhinav M. and Arias, Ana Claudia},
    title = {Understanding the Effects of Electrode Formulation on the Mechanical Strength of Composite Electrodes for Flexible Batteries},
    journal = {ACS Applied Materials \& Interfaces},
    volume = {0},
    number = {0},
    pages = {null},
    year = {2017},
    doi = {10.1021/acsami.6b14719},
    note ={PMID: 28151639},
    URL = {http://dx.doi.org/10.1021/acsami.6b14719},
    abstract = { Flexible lithium-ion batteries are necessary for powering the next generation of wearable electronic devices. In most designs, the mechanical flexibility of the battery is improved by reducing the thickness of the active layers, which in turn reduces the areal capacity and energy density of the battery. The performance of a battery depends on the electrode composition, and in most flexible batteries, standard electrode formulation is used, which is not suitable for flexing. Even with considerable efforts made toward the development of flexible lithium-ion batteries, the formulation of the electrodes has received very little attention. In this study, we investigate the relation between the electrode formulation and the mechanical strength of the electrodes. Peel and drag tests are used to compare the adhesion and cohesion strength of the electrodes. The strength of an electrode is sensitive to the particle size and the choice of polymeric binder. By optimizing the electrode composition, we were able to fabricate a high areal capacity (∼2 mAh/cm2) flexible lithium-ion battery with conventional metal-based current collectors that shows superior electrochemical and mechanical performance in comparison to that of batteries with standard composition. },
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/abhinav2017understanding.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/abhinav2017understanding.pdf}
    }

2016

  • [PDF] A. Pierre and A. C. Arias, “Solution-processed image sensors on flexible substrates,” Flexible and Printed Electronics, vol. 1, iss. 4, p. 43001, 2016.

    [Abstract]

    Image sensors are ubiquitous and used in a wide variety of applications ranging from consumer products to healthcare and industrial applications. The signal-to-noise ratio (SNR) of an image increases with larger pixels, which is costly to scale using silicon and wafer-based microfabrication. On the other hand, the performance of solution-processed photodetectors and transistors is advancing considerably. The printability of these devices on plastic substrates can enable low-cost scaling of large-pixel, high SNR image sensors. In addition, the flexibility of the substrates can enable new imaging systems never possible with the rigidity of conventional sensors. In this work we review the progress made towards solution-processed image sensors on flexible substrates. The fundamental operation of image sensors using intra-pixel charge integration is first explained to introduce the figures of merit for these systems. The physics, figures of merit, and state of the art for solution-processed photodiodes and phototransistors is also overviewed. A literature survey is done on solution-processed passive and active pixel image sensors with emphasis on active-switching for intra-pixel charge integration. Finally, optics compliant with large area and flexible image sensors are reviewed.

    [Bibtex]

    @article{pierre2016solution,
    author={Adrien Pierre and Ana Claudia Arias},
    title={Solution-processed image sensors on flexible substrates},
    journal={Flexible and Printed Electronics},
    volume={1},
    number={4},
    pages={043001},
    url={http://stacks.iop.org/2058-8585/1/i=4/a=043001},
    year={2016},
    abstract={Image sensors are ubiquitous and used in a wide variety of applications ranging from consumer products to healthcare and industrial applications. The signal-to-noise ratio (SNR) of an image increases with larger pixels, which is costly to scale using silicon and wafer-based microfabrication. On the other hand, the performance of solution-processed photodetectors and transistors is advancing considerably. The printability of these devices on plastic substrates can enable low-cost scaling of large-pixel, high SNR image sensors. In addition, the flexibility of the substrates can enable new imaging systems never possible with the rigidity of conventional sensors. In this work we review the progress made towards solution-processed image sensors on flexible substrates. The fundamental operation of image sensors using intra-pixel charge integration is first explained to introduce the figures of merit for these systems. The physics, figures of merit, and state of the art for solution-processed photodiodes and phototransistors is also overviewed. A literature survey is done on solution-processed passive and active pixel image sensors with emphasis on active-switching for intra-pixel charge integration. Finally, optics compliant with large area and flexible image sensors are reviewed.},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/pierre2016solution.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/pierre2016solution.pdf}
    }
  • [PDF] [URL] Y. Khan, M. Garg, Q. Gui, M. Schadt, A. Gaikwad, D. Han, N. A. D. Yamamoto, P. Hart, R. Welte, W. Wilson, S. Czarnecki, M. Poliks, Z. Jin, K. Ghose, F. Egitto, J. Turner, and A. C. Arias, “Flexible Hybrid Electronics: Direct Interfacing of Soft and Hard Electronics for Wearable Health Monitoring,” Advanced Functional Materials, p. n/a–n/a, 2016.

    [Abstract]

    The interfacing of soft and hard electronics is a key challenge for flexible hybrid electronics. Currently, a multisubstrate approach is employed, where soft and hard devices are fabricated or assembled on separate substrates, and bonded or interfaced using connectors; this hinders the flexibility of the device and is prone to interconnect issues. Here, a single substrate interfacing approach is reported, where soft devices, i.e., sensors, are directly printed on Kapton polyimide substrates that are widely used for fabricating flexible printed circuit boards (FPCBs). Utilizing a process flow compatible with the FPCB assembly process, a wearable sensor patch is fabricated composed of inkjet-printed gold electrocardiography (ECG) electrodes and a stencil-printed nickel oxide thermistor. The ECG electrodes provide 1 mVp–p ECG signal at 4.7 cm electrode spacing and the thermistor is highly sensitive at normal body temperatures, and demonstrates temperature coefficient, α ≈ –5.84% K–1 and material constant, β ≈ 4330 K. This sensor platform can be extended to a more sophisticated multisensor platform where sensors fabricated using solution processable functional inks can be interfaced to hard electronics for health and performance monitoring, as well as internet of things applications.

    [Bibtex]

    @article{khan2016flexible,
    author = {Khan, Yasser and Garg, Mohit and Gui, Qiong and Schadt, Mark and Gaikwad, Abhinav and Han, Donggeon and Yamamoto, Natasha A. D. and Hart, Paul and Welte, Robert and Wilson, William and Czarnecki, Steve and Poliks, Mark and Jin, Zhanpeng and Ghose, Kanad and Egitto, Frank and Turner, James and Arias, Ana C.},
    title = {Flexible Hybrid Electronics: Direct Interfacing of Soft and Hard Electronics for Wearable Health Monitoring},
    journal = {Advanced Functional Materials},
    issn = {1616-3028},
    volume={},
    number={},
    pages = {},
    year={2016},
    url = {http://dx.doi.org/10.1002/adfm.201603763},
    doi = {10.1002/adfm.201603763},
    pages = {n/a–n/a},
    keywords = {flexible electronics, inkjet printing, printed electrocardiography electrodes, printed thermistors, wearable sensor patches},
    abstract = {The interfacing of soft and hard electronics is a key challenge for flexible hybrid electronics. Currently, a multisubstrate approach is employed, where soft and hard devices are fabricated or assembled on separate substrates, and bonded or interfaced using connectors; this hinders the flexibility of the device and is prone to interconnect issues. Here, a single substrate interfacing approach is reported, where soft devices, i.e., sensors, are directly printed on Kapton polyimide substrates that are widely used for fabricating flexible printed circuit boards (FPCBs). Utilizing a process flow compatible with the FPCB assembly process, a wearable sensor patch is fabricated composed of inkjet-printed gold electrocardiography (ECG) electrodes and a stencil-printed nickel oxide thermistor. The ECG electrodes provide 1 mVp–p ECG signal at 4.7 cm electrode spacing and the thermistor is highly sensitive at normal body temperatures, and demonstrates temperature coefficient, α ≈ –5.84% K–1 and material constant, β ≈ 4330 K. This sensor platform can be extended to a more sophisticated multisensor platform where sensors fabricated using solution processable functional inks can be interfaced to hard electronics for health and performance monitoring, as well as internet of things applications.},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/khan2016flexible.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/khan2016flexible.pdf}
    }
  • [PDF] [URL] J. R. Corea, B. P. Lechene, M. Lustig, and A. C. Arias, “Materials and Methods for Higher Performance Screen-Printed Flexible MRI Receive Coils,” Magnetic Resonance in Medicine, p. n/a–n/a, 2016.

    [Abstract]

    Purpose To develop methods for characterizing materials used in screen-printed MRI coils and improve signal-to-noise ratio (SNR) with new lower-loss materials. Methods An experimental apparatus was created to characterize dielectric properties of plastic substrates used in receive coils. Coils were fabricated by screen printing conductive ink onto several plastic substrates. Unloaded and sample loaded quality factor (QUnloaded/QLoaded) measurements and scans on a 3T scanner were used to characterize coil performance. An experimental method was developed to describe the relationship between a coil’s QUnloaded and the SNR it provides in images of a phantom. In addition, 3T scans of a phantom and the head of a volunteer were obtained with a proof-of-concept printed eight-channel array, and the results were compared with a commercial 12-channel array. Results Printed coils with optimized substrates exhibited up to 97% of the image SNR when compared with a traditional coil on a loading phantom. QUnloaded and the SNR of coils were successfully correlated. The printed array resulted in images comparable to the quality given by the commercial array. Conclusion Using the proposed methods and materials, the SNR of printed coils approached that of commercial coils while using a new fabrication technique that provided more flexibility and close contact with the patient’s body. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine

    [Bibtex]

    @article{corea2016materials,
    author = {Corea, Joseph R. and Lechene, P. Balthazar and Lustig, Michael and Arias, Ana C.},
    title = {Materials and Methods for Higher Performance Screen-Printed Flexible MRI Receive Coils},
    journal = {Magnetic Resonance in Medicine},
    issn = {1522-2594},
    url = {http://dx.doi.org/10.1002/mrm.26399},
    doi = {10.1002/mrm.26399},
    pages = {n/a–n/a},
    keywords = {MRI coils, flexible MRI coils, phased arrays, NMR probes, screen printing, plastic substrates},
    year = {2016},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/corea2016materials.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/corea2016materials.pdf},
    abstract = {
    Purpose
    To develop methods for characterizing materials used in screen-printed MRI coils and improve signal-to-noise ratio (SNR) with new lower-loss materials.
    Methods
    An experimental apparatus was created to characterize dielectric properties of plastic substrates used in receive coils. Coils were fabricated by screen printing conductive ink onto several plastic substrates. Unloaded and sample loaded quality factor (QUnloaded/QLoaded) measurements and scans on a 3T scanner were used to characterize coil performance. An experimental method was developed to describe the relationship between a coil’s QUnloaded and the SNR it provides in images of a phantom. In addition, 3T scans of a phantom and the head of a volunteer were obtained with a proof-of-concept printed eight-channel array, and the results were compared with a commercial 12-channel array.
    Results
    Printed coils with optimized substrates exhibited up to 97% of the image SNR when compared with a traditional coil on a loading phantom. QUnloaded and the SNR of coils were successfully correlated. The printed array resulted in images comparable to the quality given by the commercial array.
    Conclusion
    Using the proposed methods and materials, the SNR of printed coils approached that of commercial coils while using a new fabrication technique that provided more flexibility and close contact with the patient’s body. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine}
    }
  • [PDF] [URL] B. P. Lechêne, M. Cowell, A. Pierre, J. W. Evans, P. K. Wright, and A. C. Arias, “Organic solar cells and fully printed super-capacitors optimized for indoor light energy harvesting,” Nano Energy, vol. 26, pp. 631-640, 2016.

    [Abstract]

    Abstract Flexibility, lightness and printability make organic solar cells (OSC) strong candidates to power low consumption devices such as envisioned for the Internet of Things. Such devices may be placed indoors, where light levels are well below typical outdoors level. Here, we demonstrate that maximizing the efficiency of \{OSC\} for indoor operation requires specific device optimization. In particular, minimizing the dark current of the solar cells is critical to enhance their efficiency under indoor light. Cells optimized for sunlight reach 6.2% power conversion efficiency (PCE). However when measured under simulated indoor light conditions, the \{PCE\} is to 5.2%. Cells optimized for indoor operation yield 7.6% of \{PCE\} under indoor conditions. As a proof-of-concept, the solar cells are combined with fully printed super-capacitors to form a photo-rechargeable system. Such a system with a 0.475 cm2 indoor-optimized solar cell achieved a total energy conversion and storage efficiency (ECSE) of 1.57% under 1-sun, providing 26 mJ of energy and 4.1 mW of maximum power. Under simulated indoor light the system yielded an \{ECSE\} of 2.9%, while delivering 13.3 mJ and 2.8 mW. Those energy and power levels would be sufficient to power low-consumption electronic devices with low duty cycles.

    [Bibtex]

    @article{lechene2016organic,
    title = "Organic solar cells and fully printed super-capacitors optimized for indoor light energy harvesting ",
    journal = "Nano Energy ",
    volume = "26",
    number = "",
    pages = "631 – 640",
    year = "2016",
    note = "",
    issn = "2211-2855",
    doi = "10.1016/j.nanoen.2016.06.017",
    url = "http://www.sciencedirect.com/science/article/pii/S2211285516302002",
    author = "Balthazar P. Lechêne and Martin Cowell and Adrien Pierre and James W. Evans and Paul K. Wright and Ana C. Arias",
    keywords = "Organic photovoltaics",
    keywords = "Indoor",
    keywords = "Photo-rechargeable system",
    keywords = "Printed",
    keywords = "Supercapacitor ",
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/lechene2016organic.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/lechene2016organic.pdf},
    abstract = "Abstract Flexibility, lightness and printability make organic solar cells (OSC) strong candidates to power low consumption devices such as envisioned for the Internet of Things. Such devices may be placed indoors, where light levels are well below typical outdoors level. Here, we demonstrate that maximizing the efficiency of \{OSC\} for indoor operation requires specific device optimization. In particular, minimizing the dark current of the solar cells is critical to enhance their efficiency under indoor light. Cells optimized for sunlight reach 6.2% power conversion efficiency (PCE). However when measured under simulated indoor light conditions, the \{PCE\} is to 5.2%. Cells optimized for indoor operation yield 7.6% of \{PCE\} under indoor conditions. As a proof-of-concept, the solar cells are combined with fully printed super-capacitors to form a photo-rechargeable system. Such a system with a 0.475 cm2 indoor-optimized solar cell achieved a total energy conversion and storage efficiency (ECSE) of 1.57% under 1-sun, providing 26 mJ of energy and 4.1 mW of maximum power. Under simulated indoor light the system yielded an \{ECSE\} of 2.9%, while delivering 13.3 mJ and 2.8 mW. Those energy and power levels would be sufficient to power low-consumption electronic devices with low duty cycles. "
    }
  • [PDF] [URL] A. E. Ostfeld, A. M. Gaikwad, Y. Khan, and A. C. Arias, “High-performance flexible energy storage and harvesting system for wearable electronics,” Scientific Reports, vol. 6, 2016.

    [Abstract]

    This paper reports on the design and operation of a flexible power source integrating a lithium ion battery and amorphous silicon solar module, optimized to supply power to a wearable health monitoring device. The battery consists of printed anode and cathode layers based on graphite and lithium cobalt oxide, respectively, on thin flexible current collectors. It displays energy density of 6.98 mWh/cm2 and demonstrates capacity retention of 90% at 3C discharge rate and ~99% under 100 charge/discharge cycles and 600 cycles of mechanical flexing. A solar module with appropriate voltage and dimensions is used to charge the battery under both full sun and indoor illumination conditions, and the addition of the solar module is shown to extend the battery lifetime between charging cycles while powering a load. Furthermore, we show that by selecting the appropriate load duty cycle, the average load current can be matched to the solar module current and the battery can be maintained at a constant state of charge. Finally, the battery is used to power a pulse oximeter, demonstrating its effectiveness as a power source for wearable medical devices.

    [Bibtex]

    @article{ostfeld2016high,
    title={High-performance flexible energy storage and harvesting system for wearable electronics},
    author={Ostfeld, Aminy E. and Gaikwad, Abhinav M. and Khan, Yasser and Arias, Ana C.},
    issn = {2045-2322},
    journal={Scientific Reports},
    volume={6},
    year={2016},
    publisher={Nature Publishing Group},
    url = {http://www.nature.com/srep/2016/160517/srep26122/full/srep26122.html},
    doi = {10.1038/srep26122},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/ostfeld2016high.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/ostfeld2016high.pdf},
    abstract = {This paper reports on the design and operation of a flexible power source integrating a lithium ion battery and amorphous silicon solar module, optimized to supply power to a wearable health monitoring device. The battery consists of printed anode and cathode layers based on graphite and lithium cobalt oxide, respectively, on thin flexible current collectors. It displays energy density of 6.98 mWh/cm2 and demonstrates capacity retention of 90% at 3C discharge rate and ~99% under 100 charge/discharge cycles and 600 cycles of mechanical flexing. A solar module with appropriate voltage and dimensions is used to charge the battery under both full sun and indoor illumination conditions, and the addition of the solar module is shown to extend the battery lifetime between charging cycles while powering a load. Furthermore, we show that by selecting the appropriate load duty cycle, the average load current can be matched to the solar module current and the battery can be maintained at a constant state of charge. Finally, the battery is used to power a pulse oximeter, demonstrating its effectiveness as a power source for wearable medical devices.}
    }
  • [PDF] [URL] J. R. Corea, A. M. Flynn, B. Lechêne, G. Scott, G. D. Reed, P. J. Shin, M. Lustig, and A. C. Arias, “Screen-printed flexible MRI receive coils,” Nature Communications, vol. 7, 2016.

    [Abstract]

    Magnetic resonance imaging is an inherently signal-to-noise-starved technique that limits the spatial resolution, diagnostic image quality and results in typically long acquisition times that are prone to motion artefacts. This limitation is exacerbated when receive coils have poor fit due to lack of flexibility or need for padding for patient comfort. Here, we report a new approach that uses printing for fabricating receive coils. Our approach enables highly flexible, extremely lightweight conforming devices. We show that these devices exhibit similar to higher signal-to-noise ratio than conventional ones, in clinical scenarios when coils could be displaced more than 18 mm away from the body. In addition, we provide detailed material properties and components performance analysis. Prototype arrays are incorporated within infant blankets for in vivo studies. This work presents the first fully functional, printed coils for 1.5- and 3-T clinical scanners.

    [Bibtex]

    @article{corea2016screen,
    title={Screen-printed flexible MRI receive coils},
    author={Corea, Joseph R and Flynn, Anita M and Lech{\^e}ne, Balthazar and Scott, Greig and Reed, Galen D and Shin, Peter J and Lustig, Michael and Arias, Ana C},
    journal={Nature Communications},
    volume={7},
    year={2016},
    publisher={Nature Publishing Group},
    url = {http://www.nature.com/ncomms/2016/160310/ncomms10839/full/ncomms10839.html},
    doi = {110.1038/ncomms10839},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/corea2016screen.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/corea2016screen.pdf},
    abstract = {Magnetic resonance imaging is an inherently signal-to-noise-starved technique that limits the spatial resolution, diagnostic image quality and results in typically long acquisition times that are prone to motion artefacts. This limitation is exacerbated when receive coils have poor fit due to lack of flexibility or need for padding for patient comfort. Here, we report a new approach that uses printing for fabricating receive coils. Our approach enables highly flexible, extremely lightweight conforming devices. We show that these devices exhibit similar to higher signal-to-noise ratio than conventional ones, in clinical scenarios when coils could be displaced more than 18 mm away from the body. In addition, we provide detailed material properties and components performance analysis. Prototype arrays are incorporated within infant blankets for in vivo studies. This work presents the first fully functional, printed coils for 1.5- and 3-T clinical scanners.}
    }
  • [PDF] [URL] A. M. Zamarayeva, A. M. Gaikwad, I. Deckman, M. Wang, B. Khau, D. A. Steingart, and A. C. Arias, “Fabrication of a High-Performance Flexible Silver–Zinc Wire Battery,” Advanced Electronic Materials, 2016.

    [Abstract]

    Fabrication of a flexible wire battery assembled by utilizing low-cost fabrication processes and based on silver–zinc chemistry is reported. It offers unique versatility in terms of integration with wearable technologies due to its omnidirectional flexibility and improved performance characteristics. The battery is stable over 170 cycles with capacity retention above 98% and has linear capacity ranging between 1.2 and 1.8 mAh cm−1 at 0.5C discharge rate.

    [Bibtex]

    @article{zamarayeva2016fabrication,
    author = {Zamarayeva, Alla M. and Gaikwad, Abhinav M. and Deckman, Igal and Wang, Michael and Khau, Brian and Steingart, Daniel A. and Arias, Ana Claudia},
    title = {Fabrication of a High-Performance Flexible Silver–Zinc Wire Battery},
    journal = {Advanced Electronic Materials},
    issn = {2199-160X},
    volume={},
    number={},
    pages = {},
    url = {http://dx.doi.org/10.1002/aelm.201500296},
    doi = {10.1002/aelm.201500296},
    keywords = {flexible batteries, flexible electronics, silver–zinc batteries, wire-shaped batteries},
    year = {2016},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/zamarayeva2016fabrication.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/zamarayeva2016fabrication.pdf},
    publisher={Wiley-VCH},
    abstract = {Fabrication of a flexible wire battery assembled by utilizing low-cost fabrication processes and based on silver–zinc chemistry is reported. It offers unique versatility in terms of integration with wearable technologies due to its omnidirectional flexibility and improved performance characteristics. The battery is stable over 170 cycles with capacity retention above 98% and has linear capacity ranging between 1.2 and 1.8 mAh cm−1 at 0.5C discharge rate.}
    }
  • [PDF] [URL] Y. Khan, A. E. Ostfeld, C. M. Lochner, A. Pierre, and A. C. Arias, “Monitoring of Vital Signs with Flexible and Wearable Medical Devices,” Advanced Materials, 2016.

    [Abstract]

    Advances in wireless technologies, low-power electronics, the internet of things, and in the domain of connected health are driving innovations in wearable medical devices at a tremendous pace. Wearable sensor systems composed of flexible and stretchable materials have the potential to better interface to the human skin, whereas silicon-based electronics are extremely efficient in sensor data processing and transmission. Therefore, flexible and stretchable sensors combined with low-power silicon-based electronics are a viable and efficient approach for medical monitoring. Flexible medical devices designed for monitoring human vital signs, such as body temperature, heart rate, respiration rate, blood pressure, pulse oxygenation, and blood glucose have applications in both fitness monitoring and medical diagnostics. As a review of the latest development in flexible and wearable human vitals sensors, the essential components required for vitals sensors are outlined and discussed here, including the reported sensor systems, sensing mechanisms, sensor fabrication, power, and data processing requirements.

    [Bibtex]

    @article{khan2016monitoring,
    author = {Khan, Yasser and Ostfeld, Aminy E. and Lochner, Claire M. and Pierre, Adrien and Arias, Ana C.},
    title = {Monitoring of Vital Signs with Flexible and Wearable Medical Devices},
    journal = {Advanced Materials},
    issn = {1521-4095},
    volume={},
    number={},
    pages = {},
    year={2016},
    url = {http://onlinelibrary.wiley.com/doi/10.1002/adma.201504366/abstract},
    doi = {10.1002/adma.201504366},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/khan2016monitoring.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/khan2016monitoring.pdf},
    publisher={Wiley-VCH},
    abstract = {Advances in wireless technologies, low-power electronics, the internet of things, and in the domain of connected health are driving innovations in wearable medical devices at a tremendous pace. Wearable sensor systems composed of flexible and stretchable materials have the potential to better interface to the human skin, whereas silicon-based electronics are extremely efficient in sensor data processing and transmission. Therefore, flexible and stretchable sensors combined with low-power silicon-based electronics are a viable and efficient approach for medical monitoring. Flexible medical devices designed for monitoring human vital signs, such as body temperature, heart rate, respiration rate, blood pressure, pulse oxygenation, and blood glucose have applications in both fitness monitoring and medical diagnostics. As a review of the latest development in flexible and wearable human vitals sensors, the essential components required for vitals sensors are outlined and discussed here, including the reported sensor systems, sensing mechanisms, sensor fabrication, power, and data processing requirements.},
    keywords = {flexible electronics, flexible medical sensors, printed electronics, wearable health monitoring, wearable sensors}
    }
  • [PDF] [URL] Y. Khan, F. J. Pavinatto, M. C. Lin, A. Liao, S. L. Swisher, K. Mann, V. Subramanian, M. M. Maharbiz, and A. C. Arias, “Inkjet-Printed Flexible Gold Electrode Arrays for Bioelectronic Interfaces,” Advanced Functional Materials, 2016.
    Cover Article.
    [Abstract]
    Bioelectronic interfaces require electrodes that are mechanically flexible and chemically inert. Flexibility allows pristine electrode contact to skin and tissue, and chemical inertness prevents electrodes from reacting with biological fluids and living tissues. Therefore, flexible gold electrodes are ideal for bioimpedance and biopotential measurements such as bioimpedance tomography, electrocardiography (ECG), electroencephalography (EEG), and electromyography (EMG). However, a manufacturing process to fabricate gold electrode arrays on plastic substrates is still elusive. In this work, a fabrication and low-temperature sintering (≈200 °C) technique is demonstrated to fabricate gold electrodes. At low-temperature sintering conditions, lines of different widths demonstrate different sintering speeds. Therefore, the sintering condition is targeted toward the widest feature in the design layout. Manufactured electrodes show minimum feature size of 62 μm and conductivity values of 5 × 10 6 S m−1. Utilizing the versatility of printing and plastic electronic processes, electrode arrays consisting of 31 electrodes with electrode-to-electrode spacing ranging from 2 to 7 mm are fabricated and used for impedance mapping of conformal surfaces at 15 kHz. Overall, the fabrication process of an inkjet-printed gold electrode array that is electrically reproducible, mechanically robust, and promising for bioimpedance and biopotential measurements is demonstrated.

    [Bibtex]

    @article{khan2016inkjet,
    author = {Khan, Yasser and Pavinatto, Felippe J. and Lin, Monica C. and Liao, Amy and Swisher, Sarah L. and Mann, Kaylee and Subramanian, Vivek and Maharbiz, Michel M. and Arias, Ana C.},
    title = {Inkjet-Printed Flexible Gold Electrode Arrays for Bioelectronic Interfaces},
    journal = {Advanced Functional Materials},
    issn = {1616-3028},
    volume={},
    number={},
    pages = {},
    year={2016},
    url = {http://onlinelibrary.wiley.com/doi/10.1002/adfm.201503316/abstract},
    doi = {10.1002/adfm.201503316},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/khan2016inkjet.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/khan2016inkjet.pdf},
    publisher={Wiley-VCH},
    abstract = {Bioelectronic interfaces require electrodes that are mechanically flexible and chemically inert. Flexibility allows pristine electrode contact to skin and tissue, and chemical inertness prevents electrodes from reacting with biological fluids and living tissues. Therefore, flexible gold electrodes are ideal for bioimpedance and biopotential measurements such as bioimpedance tomography, electrocardiography (ECG), electroencephalography (EEG), and electromyography (EMG). However, a manufacturing process to fabricate gold electrode arrays on plastic substrates is still elusive. In this work, a fabrication and low-temperature sintering (≈200 °C) technique is demonstrated to fabricate gold electrodes. At low-temperature sintering conditions, lines of different widths demonstrate different sintering speeds. Therefore, the sintering condition is targeted toward the widest feature in the design layout. Manufactured electrodes show minimum feature size of 62 μm and conductivity values of 5 × 10 6 S m−1. Utilizing the versatility of printing and plastic electronic processes, electrode arrays consisting of 31 electrodes with electrode-to-electrode spacing ranging from 2 to 7 mm are fabricated and used for impedance mapping of conformal surfaces at 15 kHz. Overall, the fabrication process of an inkjet-printed gold electrode array that is electrically reproducible, mechanically robust, and promising for bioimpedance and biopotential measurements is demonstrated.},
    keywords = {bioimpedance and biopotential electrodes, gold nanoparticles, inkjet printing, printed electrodes, wearable sensors},
    note = {Cover Article.}
    }
  • [PDF] [URL] A. M. Gaikwad, Y. Khan, A. E. Ostfeld, S. Pandya, S. Abraham, and A. C. Arias, “Identifying orthogonal solvents for solution processed organic transistors,” Organic Electronics, vol. 30, pp. 18-29, 2016.
    Solvents visualization program is available in the Downloads section.
    [Abstract]
    Abstract Identification of solvents for dissolving polymer dielectrics and organic semiconductors is necessary for the fabrication of solution-processed organic field effect transistors (OFETs). In addition to solubility and printability of a solvent, orthogonality is particularly important when forming multilayer structure from solutions. Currently, the process of finding orthogonal solvents is empirical, and based on trial-and-error experimental methods. In this paper, we present a methodology for identifying orthogonal solvents for solution-processed organic devices. We study the accuracy of Hildebrand and Hansen solubility theories for building solubility boundaries for organic semiconductor (Poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTT) and polymer dielectrics (Poly(methyl methacrylate) (PMMA), Polystyrene (PS)). The Hansen solubility sphere for the organic semiconductor and polymer gate dielectrics are analyzed to identify solvents that dissolve \{PMMA\} and PS, but are orthogonal to PBTTT. Top gate/bottom contact \{PBTTT\} based \{OFETs\} are fabricated with \{PMMA\} gate dielectric processed with solvents that are orthogonal and non-orthogonal to PBTTT. The non-orthogonal solvents swell the semiconductor layer and increase their surface roughness.

    [Bibtex]

    @article{gaikwad2016identifying,
    title={Identifying orthogonal solvents for solution processed organic transistors},
    author={Abhinav M. Gaikwad and Yasser Khan and Aminy E. Ostfeld and Shishir Pandya and Sameer Abraham and Ana Claudia Arias},
    journal={Organic Electronics},
    volume={30},
    pages={18 – 29},
    year={2016},
    issn={1566-1199},
    url = {http://www.sciencedirect.com/science/article/pii/S1566119915302299},
    doi = {10.1016/j.orgel.2015.12.008},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/gaikwad2016identifying.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/gaikwad2016identifying.pdf},
    publisher={},
    abstract = {Abstract Identification of solvents for dissolving polymer dielectrics and organic semiconductors is necessary for the fabrication of solution-processed organic field effect transistors (OFETs). In addition to solubility and printability of a solvent, orthogonality is particularly important when forming multilayer structure from solutions. Currently, the process of finding orthogonal solvents is empirical, and based on trial-and-error experimental methods. In this paper, we present a methodology for identifying orthogonal solvents for solution-processed organic devices. We study the accuracy of Hildebrand and Hansen solubility theories for building solubility boundaries for organic semiconductor (Poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene (PBTTT) and polymer dielectrics (Poly(methyl methacrylate) (PMMA), Polystyrene (PS)). The Hansen solubility sphere for the organic semiconductor and polymer gate dielectrics are analyzed to identify solvents that dissolve \{PMMA\} and PS, but are orthogonal to PBTTT. Top gate/bottom contact \{PBTTT\} based \{OFETs\} are fabricated with \{PMMA\} gate dielectric processed with solvents that are orthogonal and non-orthogonal to PBTTT. The non-orthogonal solvents swell the semiconductor layer and increase their surface roughness.},
    note = {Solvents visualization program is available in the Downloads section.}
    }

2015

  • [PDF] [URL] A. E. Ostfeld, I. Deckman, A. M. Gaikwad, C. M. Lochner, and A. C. Arias, “Screen printed passive components for flexible power electronics,” Scientific Reports, vol. 5, p. 15959, 2015.

    [Abstract]

    Additive and low-temperature printing processes enable the integration of diverse electronic devices, both power-supplying and power-consuming, on flexible substrates at low cost. Production of a complete electronic system from these devices, however, often requires power electronics to convert between the various operating voltages of the devices. Passive components—inductors, capacitors, and resistors—perform functions such as filtering, short-term energy storage, and voltage measurement, which are vital in power electronics and many other applications. In this paper, we present screen-printed inductors, capacitors, resistors and an RLC circuit on flexible plastic substrates, and report on the design process for minimization of inductor series resistance that enables their use in power electronics. Printed inductors and resistors are then incorporated into a step-up voltage regulator circuit. Organic light-emitting diodes and a flexible lithium ion battery are fabricated and the voltage regulator is used to power the diodes from the battery, demonstrating the potential of printed passive components to replace conventional surface-mount components in a DC-DC converter application.

    [Bibtex]

    @article{ostfeld2015screen,
    title={Screen printed passive components for flexible power electronics},
    author={Ostfeld, Aminy E. and Deckman, Igal and Gaikwad, Abhinav M. and Lochner, Claire M. and Arias, Ana C.},
    journal={Scientific Reports},
    year={2015},
    volume = {5},
    pages = {15959},
    url = {http://www.nature.com/articles/srep15959},
    doi = {10.1038/srep15959},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/ostfeld2015screen.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/ostfeld2015screen.pdf},
    publisher={Nature Publishing Group},
    abstract = {Additive and low-temperature printing processes enable the integration of diverse electronic devices, both power-supplying and power-consuming, on flexible substrates at low cost. Production of a complete electronic system from these devices, however, often requires power electronics to convert between the various operating voltages of the devices. Passive components—inductors, capacitors, and resistors—perform functions such as filtering, short-term energy storage, and voltage measurement, which are vital in power electronics and many other applications. In this paper, we present screen-printed inductors, capacitors, resistors and an RLC circuit on flexible plastic substrates, and report on the design process for minimization of inductor series resistance that enables their use in power electronics. Printed inductors and resistors are then incorporated into a step-up voltage regulator circuit. Organic light-emitting diodes and a flexible lithium ion battery are fabricated and the voltage regulator is used to power the diodes from the battery, demonstrating the potential of printed passive components to replace conventional surface-mount components in a DC-DC converter application.}
    }
  • [PDF] [URL] A. Pierre, I. Deckman, P. B. Lechêne, and A. C. Arias, “High Detectivity All-Printed Organic Photodiodes,” Advanced Materials, 2015.

    [Abstract]

    All-printed organic photodiode arrays on plastic are reported with average specific detectivities of 3.45 × 1013 cm Hz0.5 W−1 at a bias of −5 V. The blade-coated polyethylenimine cathode interlayer and active layer and screen-printed anode enable precise device performance tunability and excellent homogeneity at centimetric scales. These devices’ high operational reverse bias, good linear dynamic range, and bias stress stability make them attractive for implementation in imaging systems.

    [Bibtex]

    @article {pierre2015high,
    author = {Pierre, Adrien and Deckman, Igal and Lechêne, Pierre Balthazar and Arias, Ana Claudia},
    title = {High Detectivity All-Printed Organic Photodiodes},
    journal = {Advanced Materials},
    issn = {1521-4095},
    url = {http://dx.doi.org/10.1002/adma.201502238},
    doi = {10.1002/adma.201502238},
    year = {2015},
    abstract = {All-printed organic photodiode arrays on plastic are reported with average specific detectivities of 3.45 × 1013 cm Hz0.5 W−1 at a bias of −5 V. The blade-coated polyethylenimine cathode interlayer and active layer and screen-printed anode enable precise device performance tunability and excellent homogeneity at centimetric scales. These devices’ high operational reverse bias, good linear dynamic range, and bias stress stability make them attractive for implementation in imaging systems.},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/pierre2015high.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/pierre2015high.pdf}
    }
  • [PDF] [URL] N. A. D. Yamamoto, M. E. Payne, M. Koehler, A. Facchetti, L. S. Roman, and A. C. Arias, “Charge transport model for photovoltaic devices based on printed polymer: Fullerene nanoparticles,” Solar Energy Materials and Solar Cells, vol. 141, pp. 171-177, 2015.

    [Abstract]

    Abstract The electrical transport properties of films derived from aqueous semiconducting nanoparticle are fully described by a phenomenological model that relates intrinsic film morphology to photovoltaic response. The model is applied to a new bulk heterojunction blend, composed of organic semiconducting nanoparticles formed from the polymer donor poly[{2,6-(4,8-didodecylbenzo[1,2-b:4,5-b’]dithiophene)}-alt-{5,5-(2,5-bis(2-butyloctyl)-3,6-dithiophen-2-yl-2,5dihydropyrrolo[3,4-c]57pyrrole-1,4-dione)}] (P(TBT-DPP)) and the fullerene indene-C60-bisadduct (ICBA) synthesized by the miniemulsion method. The nanoparticle inks are printed from an aqueous dispersion onto flexible ITO-free substrates yielding power conversion efficiency of 2.6%.

    [Bibtex]

    @article{yamamoto2015charge,
    title = "Charge transport model for photovoltaic devices based on printed polymer: Fullerene nanoparticles ",
    journal = "Solar Energy Materials and Solar Cells ",
    volume = "141",
    number = "",
    pages = "171 – 177",
    year = "2015",
    note = "",
    issn = "0927-0248",
    doi = "10.1016/j.solmat.2015.05.034",
    url = "http://www.sciencedirect.com/science/article/pii/S0927024815002457",
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/yamamoto2015charge.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/yamamoto2015charge.pdf},
    author = "Natasha A.D. Yamamoto and Margaret E. Payne and Marlus Koehler and Antonio Facchetti and Lucimara S. Roman and Ana C. Arias",
    abstract = "Abstract The electrical transport properties of films derived from aqueous semiconducting nanoparticle are fully described by a phenomenological model that relates intrinsic film morphology to photovoltaic response. The model is applied to a new bulk heterojunction blend, composed of organic semiconducting nanoparticles formed from the polymer donor poly[{2,6-(4,8-didodecylbenzo[1,2-b:4,5-b’]dithiophene)}-alt-{5,5-(2,5-bis(2-butyloctyl)-3,6-dithiophen-2-yl-2,5dihydropyrrolo[3,4-c]57pyrrole-1,4-dione)}] (P(TBT-DPP)) and the fullerene indene-C60-bisadduct (ICBA) synthesized by the miniemulsion method. The nanoparticle inks are printed from an aqueous dispersion onto flexible ITO-free substrates yielding power conversion efficiency of 2.6%. "
    }
  • [PDF] A. M. Gaikwad, A. C. Arias, and D. A. Steingart, “Recent Progress on Printed Flexible Batteries: Mechanical Challenges, Printing Technologies, and Future Prospects,” Energy Technology, 2015.

    [Bibtex]

    @article{gaikwad2015recent,
    title={Recent Progress on Printed Flexible Batteries: Mechanical Challenges, Printing Technologies, and Future Prospects},
    author={Gaikwad, Abhinav M and Arias, Ana Claudia and Steingart, Daniel A},
    journal={Energy Technology},
    year={2015},
    publisher={WILEY-VCH Verlag}
    }
  • [PDF] [URL] S. L. Swisher, M. C. Lin, A. Liao, E. J. Leeflang, Y. Khan, F. J. Pavinatto, K. Mann, A. Naujokas, D. Young, S. Roy, and others, “Impedance sensing device enables early detection of pressure ulcers in vivo,” Nature Communications, vol. 6, iss. 6575, 2015.
    Media Coverage: [LINK]UC Berkeley News Center, [LINK]Futurity, [LINK]BBC News, [LINK]and many more.
    [Abstract]
    When pressure is applied to a localized area of the body for an extended time, the resulting loss of blood flow and subsequent reperfusion to the tissue causes cell death and a pressure ulcer develops. Preventing pressure ulcers is challenging because the combination of pressure and time that results in tissue damage varies widely between patients, and the underlying damage is often severe by the time a surface wound becomes visible. Currently, no method exists to detect early tissue damage and enable intervention. Here we demonstrate a flexible, electronic device that non-invasively maps pressure-induced tissue damage, even when such damage cannot be visually observed. Using impedance spectroscopy across flexible electrode arrays in vivo on a rat model, we find that impedance is robustly correlated with tissue health across multiple animals and wound types. Our results demonstrate the feasibility of an automated, non-invasive ‘smart bandage’ for early detection of pressure ulcers.

    [Bibtex]

    @article{swisher2015impedance,
    title={Impedance sensing device enables early detection of pressure ulcers in vivo},
    author={Swisher, Sarah L and Lin, Monica C and Liao, Amy and Leeflang, Elisabeth J and Khan, Yasser and Pavinatto, Felippe J and Mann, Kaylee and Naujokas, Agne and Young, David and Roy, Shuvo and others},
    journal={Nature Communications},
    volume={6},
    number={6575},
    year={2015},
    url = {http://www.nature.com/ncomms/2015/150317/ncomms7575/full/ncomms7575.html},
    doi = {10.1038/ncomms7575},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/swisher2015impedance.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/swisher2015impedance.pdf},
    publisher={Nature Publishing Group},
    abstract = {When pressure is applied to a localized area of the body for an extended time, the resulting loss of blood flow and subsequent reperfusion to the tissue causes cell death and a pressure ulcer develops. Preventing pressure ulcers is challenging because the combination of pressure and time that results in tissue damage varies widely between patients, and the underlying damage is often severe by the time a surface wound becomes visible. Currently, no method exists to detect early tissue damage and enable intervention. Here we demonstrate a flexible, electronic device that non-invasively maps pressure-induced tissue damage, even when such damage cannot be visually observed. Using impedance spectroscopy across flexible electrode arrays in vivo on a rat model, we find that impedance is robustly correlated with tissue health across multiple animals and wound types. Our results demonstrate the feasibility of an automated, non-invasive ‘smart bandage’ for early detection of pressure ulcers.},
    note = {Media Coverage: },
    media_1 = {UC Berkeley News Center, },
    media_1_link = {http://newscenter.berkeley.edu/2015/03/17/smart-bandages-detect-bedsores/},
    media_2 = {Futurity, },
    media_2_link = {http://www.futurity.org/smart-bandage-bedsores-876942/},
    media_3 = {BBC News, },
    media_3_link = {http://www.bbc.com/news/health-31903367},
    media_4 = {and many more.},
    media_4_link = {http://www.altmetric.com/details.php?domain=www.nature.com&citation_id=3798805}
    }

2014

  • [PDF] [URL] C. M. Lochner*, Y. Khan*, A. Pierre*, and A. C. Arias, “All-organic optoelectronic sensor for pulse oximetry,” Nature Communications, vol. 5, iss. 5745, 2014.
    *Equal contribution. Media Coverage: [LINK]UC Berkeley Grad News, [LINK]NSF Science 360 News, [LINK]UC Berkeley News Center, [LINK]Phys.org, [LINK]ScienceDaily, [LINK]and many more.
    [Abstract]
    Pulse oximetry is a ubiquitous non-invasive medical sensing method for measuring pulse rate and arterial blood oxygenation. Conventional pulse oximeters use expensive optoelectronic components that restrict sensing locations to finger tips or ear lobes due to their rigid form and area-scaling complexity. In this work, we report a pulse oximeter sensor based on organic materials, which are compatible with flexible substrates. Green (532 nm) and red (626 nm) organic light-emitting diodes (OLEDs) are used with an organic photodiode (OPD) sensitive at the aforementioned wavelengths. The sensor’s active layers are deposited from solution-processed materials via spin-coating and printing techniques. The all-organic optoelectronic oximeter sensor is interfaced with conventional electronics at 1 kHz and the acquired pulse rate and oxygenation are calibrated and compared with a commercially available oximeter. The organic sensor accurately measures pulse rate and oxygenation with errors of 1% and 2%, respectively.

    [Bibtex]

    @article{lochner2014all,
    title={All-organic optoelectronic sensor for pulse oximetry},
    author={Lochner*, Claire M and Khan*, Yasser and Pierre*, Adrien and Arias, Ana C},
    journal={Nature Communications},
    volume={5},
    number={5745},
    year={2014},
    url = {http://www.nature.com/ncomms/2014/141210/ncomms6745/full/ncomms6745.html},
    doi = {10.1038/ncomms6745},
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/lochner2014all.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/lochner2014all.pdf},
    publisher={Nature Publishing Group},
    abstract = {Pulse oximetry is a ubiquitous non-invasive medical sensing method for measuring pulse rate and arterial blood oxygenation. Conventional pulse oximeters use expensive optoelectronic components that restrict sensing locations to finger tips or ear lobes due to their rigid form and area-scaling complexity. In this work, we report a pulse oximeter sensor based on organic materials, which are compatible with flexible substrates. Green (532 nm) and red (626 nm) organic light-emitting diodes (OLEDs) are used with an organic photodiode (OPD) sensitive at the aforementioned wavelengths. The sensor’s active layers are deposited from solution-processed materials via spin-coating and printing techniques. The all-organic optoelectronic oximeter sensor is interfaced with conventional electronics at 1 kHz and the acquired pulse rate and oxygenation are calibrated and compared with a commercially available oximeter. The organic sensor accurately measures pulse rate and oxygenation with errors of 1% and 2%, respectively.},
    note = {*Equal contribution. Media Coverage: },
    media_1 = {UC Berkeley Grad News, },
    media_1_link = {http://grad.berkeley.edu/news/headlines/engineering-team-invents-medical-sensor/},
    media_2 = {NSF Science 360 News, },
    media_2_link = {http://news.science360.gov/obj/story/d8f7fa4c-4e41-4bcb-8ccd-1939dc4af3da/organic-electronics-lead-cheap-wearable-medical-sensors},
    media_3 = {UC Berkeley News Center, },
    media_3_link = {http://newscenter.berkeley.edu/2014/12/10/organic-electronics-cheap-wearable-medical-sensors/},
    media_4 = {Phys.org, },
    media_4_link = {http://phys.org/news/2014-12-electronics-cheap-wearable-medical-sensors.html},
    media_5 = {ScienceDaily, },
    media_5_link = {http://www.sciencedaily.com/releases/2014/12/141210131356.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily%2Ftop_news+%28ScienceDaily%3A+Top+News%29},
    media_6 = {and many more.},
    media_6_link = {http://www.altmetric.com/details.php?domain=www.nature.com&citation_id=2972740}
    }
  • [PDF] F. J. Pavinatto, C. W. Paschoal, and A. C. Arias, “Printed and flexible biosensor for antioxidants using interdigitated ink-jetted electrodes and gravure-deposited active layer,” Biosensors and Bioelectronics, 2014.

    [Bibtex]

    @article{pavinatto2014printed,
    title={Printed and flexible biosensor for antioxidants using interdigitated ink-jetted electrodes and gravure-deposited active layer},
    author={Pavinatto, Felippe J and Paschoal, Carlos WA and Arias, Ana C},
    journal={Biosensors and Bioelectronics},
    year={2014},
    publisher={Elsevier}
    }
  • [PDF] A. M. Gaikwad, B. V. Khau, G. Davies, B. Hertzberg, D. A. Steingart, and A. C. Arias, “A High Areal Capacity Flexible Lithium-Ion Battery with a Strain-Compliant Design,” Advanced Energy Materials, 2014.

    [Bibtex]

    @article{gaikwad2014high,
    title={A High Areal Capacity Flexible Lithium-Ion Battery with a Strain-Compliant Design},
    author={Gaikwad, Abhinav M and Khau, Brian V and Davies, Greg and Hertzberg, Benjamin and Steingart, Daniel A and Arias, Ana Claudia},
    journal={Advanced Energy Materials},
    year={2014}
    }
  • [PDF] A. Pierre, M. Sadeghi, M. M. Payne, A. Facchetti, J. E. Anthony, and A. C. Arias, “All-Printed Flexible Organic Transistors Enabled by Surface Tension-Guided Blade Coating,” Advanced Materials, vol. 26, iss. 32, pp. 5722-5727, 2014.

    [Bibtex]

    @article{pierre2014all,
    title={All-Printed Flexible Organic Transistors Enabled by Surface Tension-Guided Blade Coating},
    author={Pierre, Adrien and Sadeghi, Mahsa and Payne, Marcia M and Facchetti, Antonio and Anthony, John E and Arias, Ana Claudia},
    journal={Advanced Materials},
    volume={26},
    number={32},
    pages={5722–5727},
    year={2014}
    }
  • [PDF] [URL] A. E. Ostfeld, A. Catheline, K. Ligsay, K. Kim, Z. Chen, A. Facchetti, S. Fogden, and A. C. Arias, “Single-walled carbon nanotube transparent conductive films fabricated by reductive dissolution and spray coating for organic photovoltaics,” Applied Physics Letters, vol. 105, iss. 25, p. -, 2014.

    [Bibtex]

    @article{ostfeld2014single,
    author = "Ostfeld, Aminy E. and Catheline, Amélie and Ligsay, Kathleen and Kim, Kee-Chan and Chen, Zhihua and Facchetti, Antonio and Fogden, Siân and Arias, Ana Claudia",
    title = "Single-walled carbon nanotube transparent conductive films fabricated by reductive dissolution and spray coating for organic photovoltaics",
    journal = "Applied Physics Letters",
    year = "2014",
    volume = "105",
    number = "25",
    eid = 253301,
    pages = "-",
    url = "http://scitation.aip.org/content/aip/journal/apl/105/25/10.1063/1.4904940",
    doi = "http://dx.doi.org/10.1063/1.4904940"
    }

2013

  • [PDF] [URL] A. Pierre, S. Lu, I. A. Howard, A. Facchetti, and A. C. Arias, “Empirically based device modeling of bulk heterojunction organic photovoltaics,” Journal of Applied Physics, vol. 113, iss. 15, 2013.
    Bulk heterojunction device model simulator package is available in the Downloads section.
    [Abstract]
    We develop an empirically based optoelectronic model to accurately simulate the photocurrent in organic photovoltaic (OPV) devices with novel materials including bulk heterojunction OPV devices based on a new low band gap dithienothiophene-DPP donor polymer, P(TBT-DPP), blended with PC70BM at various donor-acceptor weight ratios and solvent compositions. Our devices exhibit power conversion efficiencies ranging from 1.8% to 4.7% at AM 1.5G. Electron and hole mobilities are determined using space-charge limited current measurements. Bimolecular recombination coefficients are both analytically calculated using slowest-carrier limited Langevin recombination and measured using an electro-optical pump-probe technique. Exciton quenching efficiencies in the donor and acceptor domains are determined from photoluminescence spectroscopy. In addition, dielectric and optical constants are experimentally determined. The photocurrent and its bias-dependence that we simulate using the optoelectronic model we develop, which takes into account these physically measured parameters, shows less than 7% error with respect to the experimental photocurrent (when both experimentally and semi-analytically determined recombination coefficient is used). Free carrier generation and recombination rates of the photocurrent are modeled as a function of the position in the active layer at various applied biases. These results show that while free carrier generation is maximized in the center of the device, free carrier recombination is most dominant near the electrodes even in high performance devices. Such knowledge of carrier activity is essential for the optimization of the active layer by enhancing light trapping and minimizing recombination. Our simulation program is intended to be freely distributed for use in laboratories fabricating OPV devices.

    [Bibtex]

    @article{pierre2013empirically,
    author = "Pierre, Adrien and Lu, Shaofeng and Howard, Ian A. and Facchetti, Antonio and Arias, Ana Claudia",
    title = "Empirically based device modeling of bulk heterojunction organic photovoltaics",
    journal = "Journal of Applied Physics",
    year = "2013",
    volume = "113",
    number = "15",
    eid = 154506,
    pages = "",
    url = "http://scitation.aip.org/content/aip/journal/jap/113/15/10.1063/1.4801662",
    doi = "10.1063/1.4801662",
    thumbnail = {https://www.ocf.berkeley.edu/~arias/public/publications/files/pierre2013empirically.png},
    pdf = {https://www.ocf.berkeley.edu/~arias/public/publications/files/pierre2013empirically.pdf},
    publisher={},
    abstract = {We develop an empirically based optoelectronic model to accurately simulate the photocurrent in organic photovoltaic (OPV) devices with novel materials including bulk heterojunction OPV devices based on a new low band gap dithienothiophene-DPP donor polymer, P(TBT-DPP), blended with PC70BM at various donor-acceptor weight ratios and solvent compositions. Our devices exhibit power conversion efficiencies ranging from 1.8% to 4.7% at AM 1.5G. Electron and hole mobilities are determined using space-charge limited current measurements. Bimolecular recombination coefficients are both analytically calculated using slowest-carrier limited Langevin recombination and measured using an electro-optical pump-probe technique. Exciton quenching efficiencies in the donor and acceptor domains are determined from photoluminescence spectroscopy. In addition, dielectric and optical constants are experimentally determined. The photocurrent and its bias-dependence that we simulate using the optoelectronic model we develop, which takes into account these physically measured parameters, shows less than 7% error with respect to the experimental photocurrent (when both experimentally and semi-analytically determined recombination coefficient is used). Free carrier generation and recombination rates of the photocurrent are modeled as a function of the position in the active layer at various applied biases. These results show that while free carrier generation is maximized in the center of the device, free carrier recombination is most dominant near the electrodes even in high performance devices. Such knowledge of carrier activity is essential for the optimization of the active layer by enhancing light trapping and minimizing recombination. Our simulation program is intended to be freely distributed for use in laboratories fabricating OPV devices.},
    note = {Bulk heterojunction device model simulator package is available in the Downloads section.}
    }

2012

  • J. H. Daniel, A. C. Arias, and M. Chabinyc, Method and structure for establishing contacts in thin film transistor devices, 2012.
    US Patent 20,120,322,214
    [Bibtex]
    @misc{daniel2012method,
    title={Method and structure for establishing contacts in thin film transistor devices},
    author={Daniel, J{\"u}rgen H and Arias, Ana Claudia and Chabinyc, Michael},
    year={2012},
    month=dec # "~20",
    note={US Patent 20,120,322,214}
    }
  • S. Sambandan, A. C. Arias, and G. L. Whiting, Thin Film Field Effect Transistor with Dual Semiconductor Layers, 2012.
    US Patent 20,120,007,079
    [Bibtex]
    @misc{sambandan2012thin,
    title={Thin Film Field Effect Transistor with Dual Semiconductor Layers},
    author={Sambandan, Sanjiv and Arias, Ana Claudia and Whiting, Gregory Lewis},
    year={2012},
    month=jan # "~12",
    note={US Patent 20,120,007,079}
    }
  • D. J. Mackenzie, A. C. Arias, R. H. Friend, and W. Huck, OPTOELECTRONIC DEVICES AND A METHOD FOR PRODUCING THE SAME, 2012.
    US Patent 20,120,064,652
    [Bibtex]
    @misc{mackenzie2012optoelectronic,
    title={OPTOELECTRONIC DEVICES AND A METHOD FOR PRODUCING THE SAME},
    author={Mackenzie, Devin J and Arias, Ana Claudia and Friend, Richard Henry and Huck, Wilhelm},
    year={2012},
    month=mar # "~15",
    note={US Patent 20,120,064,652}
    }
  • S. Sambandan, A. C. Arias, and G. L. Whiting, Thin film field effect transistor with dual semiconductor layers, 2012.
    US Patent App. 13/426,518
    [Bibtex]
    @misc{sambandan2012thin,
    title={Thin film field effect transistor with dual semiconductor layers},
    author={Sambandan, Sanjiv and Arias, Ana Claudia and Whiting, Gregory Lewis},
    year={2012},
    month=mar # "~21",
    note={US Patent App. 13/426,518}
    }
  • N. A. Yamamoto, L. L. Lavery, B. F. Nowacki, I. R. Grova, G. L. Whiting, B. Krusor, E. R. de Azevedo, L. Akcelrud, A. C. Arias, and L. S. Roman, “Synthesis and Solar Cell Application of New Alternating Donor–Acceptor Copolymers Based on Variable Units of Fluorene, Thiophene, and Phenylene,” The Journal of Physical Chemistry C, vol. 116, iss. 35, pp. 18641-18648, 2012.

    [Bibtex]

    @article{yamamoto2012synthesis,
    title={Synthesis and Solar Cell Application of New Alternating Donor–Acceptor Copolymers Based on Variable Units of Fluorene, Thiophene, and Phenylene},
    author={Yamamoto, Natasha AD and Lavery, Leah L and Nowacki, Bruno F and Grova, Isabel R and Whiting, Gregory L and Krusor, Brent and de Azevedo, Eduardo R and Akcelrud, Leni and Arias, Ana C and Roman, Lucimara S},
    journal={The Journal of Physical Chemistry C},
    volume={116},
    number={35},
    pages={18641–18648},
    year={2012},
    publisher={American Chemical Society}
    }
  • J. H. Daniel and A. C. Arias, Printed Material Constrained By Well Structures And Devices Including Same, 2012.
    US Patent 20,120,238,081
    [Bibtex]
    @misc{daniel2012printed,
    title={Printed Material Constrained By Well Structures And Devices Including Same},
    author={Daniel, Jurgen H and Arias, Ana Claudia},
    year={2012},
    month=sep # "~20",
    note={US Patent 20,120,238,081}
    }
  • J. H. Daniel and A. C. Arias, Printed Material Constrained By Well Structures And Devices Including Same, 2012.
    US Patent 20,120,235,145
    [Bibtex]
    @misc{daniel2012printed,
    title={Printed Material Constrained By Well Structures And Devices Including Same},
    author={Daniel, Jurgen H and Arias, Ana Claudia},
    year={2012},
    month=sep # "~20",
    note={US Patent 20,120,235,145}
    }
  • R. A. Street and A. C. Arias, “Conformable Active Devices,” Stretchable Electronics, pp. 355-378, 2012.

    [Bibtex]

    @article{street2012conformable,
    title={Conformable Active Devices},
    author={Street, Robert A and Arias, Ana Claudia},
    journal={Stretchable Electronics},
    pages={355–378},
    year={2012},
    publisher={Wiley-VCH Verlag GmbH \& Co. KGaA}
    }
  • J. H. Daniel and A. C. Arias, Electronic circuit structure and method for forming same, 2012.
    US Patent 20,120,302,046
    [Bibtex]
    @misc{daniel2012electronic,
    title={Electronic circuit structure and method for forming same},
    author={Daniel, J{\"u}rgen H and Arias, Ana Claudia},
    year={2012},
    month=nov # "~29",
    note={US Patent 20,120,302,046}
    }

2011

  • [URL] A. M. Gaikwad, G. L. Whiting, D. A. Steingart, and A. C. Arias, “Highly Flexible, Printed Alkaline Batteries Based on Mesh-Embedded Electrodes,” Advanced Materials, vol. 23, iss. 29, pp. 3251-3255, 2011.

    [Bibtex]

    @article {ADMA:ADMA201100894,
    author = {Gaikwad, Abhinav M. and Whiting, Gregory L. and Steingart, Daniel A. and Arias, Ana Claudia},
    title = {Highly Flexible, Printed Alkaline Batteries Based on Mesh-Embedded Electrodes},
    journal = {Advanced Materials},
    volume = {23},
    number = {29},
    publisher = {WILEY-VCH Verlag},
    issn = {1521-4095},
    url = {http://dx.doi.org/10.1002/adma.201100894},
    doi = {10.1002/adma.201100894},
    pages = {3251–3255},
    keywords = {flexible batteries, polymer electrolytes, mesh architectures, flexible electronics},
    year = {2011},
    }
  • [URL] L. L. Lavery, G. L. Whiting, and A. C. Arias, “All ink-jet printed polyfluorene photosensor for high illuminance detection,” Organic Electronics, vol. 12, iss. 4, pp. 682-685, 2011.

    [Bibtex]

    @article{Lavery2011682,
    title = "All ink-jet printed polyfluorene photosensor for high illuminance detection",
    journal = "Organic Electronics",
    volume = "12",
    number = "4",
    pages = "682 – 685",
    year = "2011",
    note = "",
    issn = "1566-1199",
    doi = "10.1016/j.orgel.2011.01.023",
    url = "http://www.sciencedirect.com/science/article/pii/S1566119911000383",
    author = "Leah Lucas Lavery and Gregory Lewis Whiting and Ana Claudia Arias",
    keywords = "Ink-jet",
    keywords = "Photosensor",
    keywords = "PFB:F8BT"
    }

2010

  • [URL] A. C. Arias, D. J. MacKenzie, I. McCulloch, J. Rivnay, and A. Salleo, “Materials and Applications for Large Area Electronics: Solution-Based Approaches,” Chemical Reviews, vol. 110, iss. 1, pp. 3-24, 2010.
    PMID: 20070114
    [Bibtex]
    @article{doi:10.1021/cr900150b,
    author = {Arias, Ana Claudia and MacKenzie, J. Devin and McCulloch, Iain and Rivnay, Jonathan and Salleo, Alberto},
    title = {Materials and Applications for Large Area Electronics: Solution-Based Approaches},
    journal = {Chemical Reviews},
    volume = {110},
    number = {1},
    pages = {3-24},
    year = {2010},
    doi = {10.1021/cr900150b},
    note ={PMID: 20070114},
    URL = {http://pubs.acs.org/doi/abs/10.1021/cr900150b},
    eprint = {http://pubs.acs.org/doi/pdf/10.1021/cr900150b}
    }
  • [URL] S. Sambandan, G. Whiting, A. Arias, and R. A. Street, “Fast polymer semiconductor transistor by nano-particle self assembly,” Organic Electronics, vol. 11, iss. 12, pp. 1935-1941, 2010.

    [Abstract]

    Polymer semiconductor based field effect transistors promise low cost electronics over rigid and flexible large area substrates using fabrication techniques such as ink-jet printing. However, the low mobility of carriers in these semiconductors does not permit high performance electronics. A primary means to achieve higher speed in spite of the low carrier mobility is to reduce feature size, particularly channel length, of the field effect transistors. In this paper, we use the controlled coffee stain effect in a silver nano-particle colloid along with ink-jet printing to develop a process which helps reduce field effect transistor channel length to about 1–10 μm and improve transistor speed.

    [Bibtex]

    @article{Sambandan20101935,
    title = "Fast polymer semiconductor transistor by nano-particle self assembly",
    journal = "Organic Electronics",
    volume = "11",
    number = "12",
    pages = "1935 – 1941",
    year = "2010",
    note = "",
    issn = "1566-1199",
    doi = "10.1016/j.orgel.2010.08.012",
    url = "http://www.sciencedirect.com/science/article/pii/S1566119910002843",
    author = "S. Sambandan and G. Whiting and A. Arias and R.A. Street",
    keywords = "Polymer semiconductors",
    keywords = "Field effect transistors",
    keywords = "Self assembly",
    keywords = "Coffee stain effect",
    abstract = "Polymer semiconductor based field effect transistors promise low cost electronics over rigid and flexible large area substrates using fabrication techniques such as ink-jet printing. However, the low mobility of carriers in these semiconductors does not permit high performance electronics. A primary means to achieve higher speed in spite of the low carrier mobility is to reduce feature size, particularly channel length, of the field effect transistors. In this paper, we use the controlled coffee stain effect in a silver nano-particle colloid along with ink-jet printing to develop a process which helps reduce field effect transistor channel length to about 1–10 μm and improve transistor speed."
    }

2009

  • [URL] T. N. Ng, S. Sambandan, R. Lujan, A. C. Arias, C. R. Newman, H. Yan, and A. Facchetti, “Electrical stability of inkjet-patterned organic complementary inverters measured in ambient conditions,” Applied Physics Letters, vol. 94, iss. 23, p. 233307, 2009.

    [Bibtex]

    @article{Tse233307,
    author = {Tse Nga Ng and Sanjiv Sambandan and Rene Lujan and Ana Claudia Arias and Christopher R. Newman and He Yan and Antonio Facchetti},
    collaboration = {},
    title = {Electrical stability of inkjet-patterned organic complementary inverters measured in ambient conditions},
    publisher = {AIP},
    year = {2009},
    journal = {Applied Physics Letters},
    volume = {94},
    number = {23},
    eid = {233307},
    numpages = {3},
    pages = {233307},
    keywords = {electron mobility; hole mobility; invertors; organic semiconductors; tantalum compounds; thin film transistors},
    url = {http://link.aip.org/link/?APL/94/233307/1},
    doi = {10.1063/1.3153510}
    }
  • [URL] G. L. Whiting and A. C. Arias, “Chemically modified ink-jet printed silver electrodes for organic field-effect transistors,” Applied Physics Letters, vol. 95, iss. 25, p. 253302, 2009.

    [Bibtex]

    @article{whiting:253302,
    author = {Gregory Lewis Whiting and Ana Claudia Arias},
    collaboration = {},
    title = {Chemically modified ink-jet printed silver electrodes for organic field-effect transistors},
    publisher = {AIP},
    year = {2009},
    journal = {Applied Physics Letters},
    volume = {95},
    number = {25},
    eid = {253302},
    numpages = {3},
    pages = {253302},
    keywords = {carrier mobility; electrodes; organic field effect transistors; organic semiconductors; silver},
    url = {http://link.aip.org/link/?APL/95/253302/1},
    doi = {10.1063/1.3276913}
    }
  • [URL] T. N. Ng, B. Russo, and A. C. Arias, “Degradation mechanisms of organic ferroelectric field-effect transistors used as nonvolatile memory,” Journal of Applied Physics, vol. 106, iss. 9, p. 94504, 2009.

    [Bibtex]

    @article{(Tse094504,
    author = {Tse Nga Ng and Beverly Russo and Ana Claudia Arias},
    collaboration = {},
    title = {Degradation mechanisms of organic ferroelectric field-effect transistors used as nonvolatile memory},
    publisher = {AIP},
    year = {2009},
    journal = {Journal of Applied Physics},
    volume = {106},
    number = {9},
    eid = {094504},
    numpages = {5},
    pages = {094504},
    keywords = {ferroelectric storage; field effect transistor circuits; hysteresis},
    url = {http://link.aip.org/link/?JAP/106/094504/1},
    doi = {10.1063/1.3253758}
    }
  • [URL] S. Sambandan, R. J. P. Kist, R. Lujan, T. Ng, A. C. Arias, and R. A. Street, “Compact model for forward subthreshold characteristics in polymer semiconductor transistors,” Journal of Applied Physics, vol. 106, iss. 8, p. 84501, 2009.

    [Bibtex]

    @article{sambandan:084501,
    author = {S. Sambandan and R. J. P. Kist and R. Lujan and T. Ng and A. C. Arias and R. A. Street},
    collaboration = {},
    title = {Compact model for forward subthreshold characteristics in polymer semiconductor transistors},
    publisher = {AIP},
    year = {2009},
    journal = {Journal of Applied Physics},
    volume = {106},
    number = {8},
    eid = {084501},
    numpages = {8},
    pages = {084501},
    keywords = {deep levels; hopping conduction; organic semiconductors; polymers; Poole-Frenkel effect; semiconductor device models; space-charge-limited conduction; thin film transistors},
    url = {http://link.aip.org/link/?JAP/106/084501/1},
    doi = {10.1063/1.3233927}
    }

2008

  • [URL] V. Sholin, S. A. Carter, R. A. Street, and A. C. Arias, “High work function materials for source/drain contacts in printed polymer thin film transistors,” Applied Physics Letters, vol. 92, iss. 6, p. 63307, 2008.

    [Bibtex]

    @article{sholin:063307,
    author = {V. Sholin and S. A. Carter and R. A. Street and A. C. Arias},
    collaboration = {},
    title = {High work function materials for source/drain contacts in printed polymer thin film transistors},
    publisher = {AIP},
    year = {2008},
    journal = {Applied Physics Letters},
    volume = {92},
    number = {6},
    eid = {063307},
    numpages = {3},
    pages = {063307},
    keywords = {electrodes; nanoparticles; polymer blends; silver; thin film transistors; work function},
    url = {http://link.aip.org/link/?APL/92/063307/1},
    doi = {10.1063/1.2857461}
    }
  • [URL] T. N. Ng, J. H. Daniel, S. Sambandan, A. Arias, M. L. Chabinyc, and R. A. Street, “Gate bias stress effects due to polymer gate dielectrics in organic thin-film transistors,” Journal of Applied Physics, vol. 103, iss. 4, p. 44506, 2008.

    [Bibtex]

    @article{ng:044506,
    author = {Tse Nga Ng and Jurgen H. Daniel and Sanjiv Sambandan and Ana-Claudia Arias and Michael L. Chabinyc and Robert A. Street},
    collaboration = {},
    title = {Gate bias stress effects due to polymer gate dielectrics in organic thin-film transistors},
    publisher = {AIP},
    year = {2008},
    journal = {Journal of Applied Physics},
    volume = {103},
    number = {4},
    eid = {044506},
    numpages = {6},
    pages = {044506},
    keywords = {capacitance; charge injection; conducting polymers; dielectric materials; organic semiconductors; thin film transistors},
    url = {http://link.aip.org/link/?JAP/103/044506/1},
    doi = {10.1063/1.2884535}
    }
  • [URL] S. Sambandan, A. C. Arias, and R. A. Street, “Timing Randomly Spaced Events Using the Threshold-Voltage Shift in Disordered Semiconductors,” Electron Devices, IEEE Transactions on, vol. 55, iss. 12, pp. 3367-3374, 2008.

    [Abstract]

    This paper discusses the concept of using the threshold-voltage shift in disordered-semiconductor-based thin- film transistors to measure the time of occurrence of randomly spaced events of interest. We call the experimental circuit an "analog clock." The analog clock is shown to be accurate while, at the same time, being simple in design using just one transistor.

    [Bibtex]

    @ARTICLE{4674578,
    author={Sambandan, S. and Arias, A.C. and Street, R.A.},
    journal={Electron Devices, IEEE Transactions on}, title={Timing Randomly Spaced Events Using the Threshold-Voltage Shift in Disordered Semiconductors},
    year={2008},
    month={dec. },
    volume={55},
    number={12},
    pages={3367 -3374},
    abstract={This paper discusses the concept of using the threshold-voltage shift in disordered-semiconductor-based thin- film transistors to measure the time of occurrence of randomly spaced events of interest. We call the experimental circuit an "analog clock." The analog clock is shown to be accurate while, at the same time, being simple in design using just one transistor.},
    keywords={analog clock;disordered-semiconductor-based thin-film transistors;randomly spaced events;threshold-voltage shift;organic semiconductors;thin film transistors;},
    doi={10.1109/TED.2008.2006549},
    ISSN={0018-9383},}

2007

  • [URL] A. Salleo and A.  C. Arias, “Solution Based Self-Assembly of an Array of Polymeric Thin-Film Transistors,” Advanced Materials, vol. 19, iss. 21, pp. 3540-3543, 2007.

    [Bibtex]

    @article {ADMA:ADMA200700445,
    author = {Salleo, A. and Arias, A. C.},
    title = {Solution Based Self-Assembly of an Array of Polymeric Thin-Film Transistors},
    journal = {Advanced Materials},
    volume = {19},
    number = {21},
    publisher = {WILEY-VCH Verlag},
    issn = {1521-4095},
    url = {http://dx.doi.org/10.1002/adma.200700445},
    doi = {10.1002/adma.200700445},
    pages = {3540–3543},
    keywords = {Self-assembly, Semiconductors, Thin-film transistors, organic},
    year = {2007},
    }
  • [URL] J. Daniel, A. C. Arias, W. Wong, R. Lujan, S. Ready, B. Krusor, and R. Street, “Jet-Printed Active-Matrix Backplanes and Electrophoretic Displays,” Japanese Journal of Applied Physics, vol. 46, iss. 3B, pp. 1363-1369, 2007.

    [Bibtex]

    @Article{JJAP.46.1363,
    title = {Jet-Printed Active-Matrix Backplanes and Electrophoretic Displays},
    author = {Jurgen Daniel and Ana Claudia Arias and William Wong and Rene Lujan and Steve Ready and Brent Krusor and Robert Street},
    journal = {Japanese Journal of Applied Physics},
    volume = {46},
    number = {3B},
    pages = {1363-1369},
    numpages = {6},
    year = {2007},
    url = {http://jjap.jsap.jp/link?JJAP/46/1363/},
    doi = {10.1143/JJAP.46.1363},
    publisher = {The Japan Society of Applied Physics}
    }
  • [URL] A. C. Arias, J. Daniel, B. Krusor, S. Ready, V. Sholin, and R. Street, “All-additive ink-jet-printed display backplanes: Materials development and integration,” Journal of the Society for Information Display, vol. 15, iss. 7, pp. 485-490, 2007.

    [Abstract]

    Abstract— Methods used to deposit and integrate solution-processed materials to fabricate TFT backplanes by ink-jet printing are discussed. Thematerials studied allow the development of an all-additive process in which materials are deposited only where their functionality is required. The metal layer and semiconductor are printed, and the solution-processed dielectric is spin-coated. Silver nanoparticles are used as gate and datametals, the semiconductor used is a polythiophene derivative (PQT-12), and the gate dielectric is an epoxy-based photopolymer. The maximum processing temperature used is 150°C, making the process compatible with flexible substrates. The ION/IOFF ratio was found to be about 105−106, and TFT mobilities of 0.04 cm2/V-sec were obtained. The influence of surface treatments on the size and shape of printed features is presented. It is shown that coffee-stain effects can be controlled with ink formulation and that devices show the expected pixel response.

    [Bibtex]

    @article {JSID:JSID1520,
    author = {Arias, Ana C. and Daniel, Jürgen and Krusor, Brent and Ready, Steve and Sholin, Veronica and Street, Robert},
    title = {All-additive ink-jet-printed display backplanes: Materials development and integration},
    journal = {Journal of the Society for Information Display},
    volume = {15},
    number = {7},
    publisher = {Blackwell Publishing Ltd},
    issn = {1938-3657},
    url = {http://dx.doi.org/10.1889/1.2759554},
    doi = {10.1889/1.2759554},
    pages = {485–490},
    keywords = {Display backplanes, organic semiconductors, TFTs, ink-jet printing},
    year = {2007},
    abstract = {Abstract— Methods used to deposit and integrate solution-processed materials to fabricate TFT backplanes by ink-jet printing are discussed. Thematerials studied allow the development of an all-additive process in which materials are deposited only where their functionality is required. The metal layer and semiconductor are printed, and the solution-processed dielectric is spin-coated. Silver nanoparticles are used as gate and datametals, the semiconductor used is a polythiophene derivative (PQT-12), and the gate dielectric is an epoxy-based photopolymer. The maximum processing temperature used is 150°C, making the process compatible with flexible substrates. The ION/IOFF ratio was found to be about 105−106, and TFT mobilities of 0.04 cm2/V-sec were obtained. The influence of surface treatments on the size and shape of printed features is presented. It is shown that coffee-stain effects can be controlled with ink formulation and that devices show the expected pixel response.},
    }

2006

  • [URL] “Thin-film Transistor Fabrication by Digital Lithography,” in Organic Electronics, Wiley-VCH Verlag GmbH & Co. KGaA, 2006, pp. 271-293.

    [Abstract]

    This chapter contains sections titled: * Introduction * Jet-printed Patterning for Thin-film Transistor Processing * Introduction * Jet-printed Phase-change Etch Masks * Digital Lithography * Digital Lithography for TFT Device Fabrication * Thin-film Transistor Device Structures * Amorphous Silicon TFTs * Polymeric TFTs by Digital Lithography * Thin-film Transistor Device Characteristics * a-Si:H TFTs * Printed Polymeric TFTs * TFTs on Flexible Substrates * Introduction * TFT Pixel Design Considerations * Digital Lithography for Flexible Backplanes * Display Applications with Print-patterned Backplanes * Conclusions * Acknowledgments * References

    [Bibtex]

    @inbook {wong2006,
    title = {Thin-film Transistor Fabrication by Digital Lithography},
    author = {Wong, William S. and Daniel, Jürgen H. and Chabinyc, Michael L. and Arias, Ana Claudia and Ready, Steven E. and Lujan, René},
    author = {},
    publisher = {Wiley-VCH Verlag GmbH & Co. KGaA},
    isbn = {9783527608751},
    url = {http://dx.doi.org/10.1002/3527608753.ch11},
    doi = {10.1002/3527608753.ch11},
    pages = {271–293},
    keywords = {organic electronics, manufacturing, thin-film transistor (TFT) fabrication, digital lithography, jet-printed patterning, TFTs on flexible substrates, display applications, print-patterned backplanes},
    booktitle = {Organic Electronics},
    year = {2006},
    abstract = {This chapter contains sections titled:
    * Introduction
    * Jet-printed Patterning for Thin-film Transistor Processing
    * Introduction
    * Jet-printed Phase-change Etch Masks
    * Digital Lithography
    * Digital Lithography for TFT Device Fabrication
    * Thin-film Transistor Device Structures
    * Amorphous Silicon TFTs
    * Polymeric TFTs by Digital Lithography
    * Thin-film Transistor Device Characteristics
    * a-Si:H TFTs
    * Printed Polymeric TFTs
    * TFTs on Flexible Substrates
    * Introduction
    * TFT Pixel Design Considerations
    * Digital Lithography for Flexible Backplanes
    * Display Applications with Print-patterned Backplanes
    * Conclusions
    * Acknowledgments
    * References},
    }
  • [URL] A. Claudia Arias, “Vertically Segregated Polymer Blends: Their Use in Organic Electronics,” Journal of Macromolecular Science, Part C: Polymer Reviews, vol. 46, iss. 1, pp. 103-125, 2006.

    [Abstract]

    In this paper results on the formation and stability of vertically segregated polymer blend structures applied to organic‐based electronic devices are reviewed. In all examples illustrated here, phase separation in a direction normal to the substrate was obtained by a combination of surface treatment, viscosity, solvent evaporation, and blend composition control. It is found that vertically segregated blends form the optimized structure for photovoltaic devices, in which exciton dissociation is enhanced by the composition of the phases and transport of charges is improved by the position of the phases relative to the electrodes. Vertical segregation is shown to reduce leakage current and enhance charge injection and recombination in light emitting diodes resulting in highly luminescent devices. In addition, film composition and morphology analysis together with device characteristics show that the environmental stability of bottom gate polymer‐based TFTs is greatly enhanced by a self‐encapsulation method achieved with the use of a semiconductor/insulator polymer blend.

    [Bibtex]

    @article{doi:10.1080/15321790500471251,
    author = {Claudia Arias, Ana},
    title = {Vertically Segregated Polymer Blends: Their Use in Organic Electronics},
    journal = {Journal of Macromolecular Science, Part C: Polymer Reviews},
    volume = {46},
    number = {1},
    pages = {103-125},
    year = {2006},
    doi = {10.1080/15321790500471251},
    URL = {http://www.tandfonline.com/doi/abs/10.1080/15321790500471251},
    eprint = {http://www.tandfonline.com/doi/pdf/10.1080/15321790500471251},
    abstract = { In this paper results on the formation and stability of vertically segregated polymer blend structures applied to organic‐based electronic devices are reviewed. In all examples illustrated here, phase separation in a direction normal to the substrate was obtained by a combination of surface treatment, viscosity, solvent evaporation, and blend composition control. It is found that vertically segregated blends form the optimized structure for photovoltaic devices, in which exciton dissociation is enhanced by the composition of the phases and transport of charges is improved by the position of the phases relative to the electrodes. Vertical segregation is shown to reduce leakage current and enhance charge injection and recombination in light emitting diodes resulting in highly luminescent devices. In addition, film composition and morphology analysis together with device characteristics show that the environmental stability of bottom gate polymer‐based TFTs is greatly enhanced by a self‐encapsulation method achieved with the use of a semiconductor/insulator polymer blend. }
    }
  • [URL] R. A. Street, W. S. Wong, S. E. Ready, M. L. Chabinyc, A. C. Arias, S. Limb, A. Salleo, and R. Lujan, “Jet printing flexible displays,” Materials Today, vol. 9, iss. 4, pp. 32-37, 2006.

    [Abstract]

    Jet printing is an interesting patterning technique for electronic devices because it requires no physical mask, has digital control of ejection, and provides good layer-to-layer registration. It also has the potential to reduce display manufacturing costs and enable roll-to-roll processing. The technique is illustrated with examples of prototype printed displays using amorphous silicon and polymer semiconductors.

    [Bibtex]

    @article{Street200632,
    title = "Jet printing flexible displays",
    journal = "Materials Today",
    volume = "9",
    number = "4",
    pages = "32 – 37",
    year = "2006",
    note = "",
    issn = "1369-7021",
    doi = "10.1016/S1369-7021(06)71445-6",
    url = "http://www.sciencedirect.com/science/article/pii/S1369702106714456",
    author = "R.A. Street and W.S. Wong and S.E. Ready and M.L. Chabinyc and A.C. Arias and S. Limb and A. Salleo and R. Lujan",
    abstract = "Jet printing is an interesting patterning technique for electronic devices because it requires no physical mask, has digital control of ejection, and provides good layer-to-layer registration. It also has the potential to reduce display manufacturing costs and enable roll-to-roll processing. The technique is illustrated with examples of prototype printed displays using amorphous silicon and polymer semiconductors."
    }
  • J. Daniel, A. C. Arias, B. Krusor, R. Lujan, and R. Street, “The Road Towards Large-Area Electronics Without Vacuum Tools,” Meeting Abstracts, vol. MA2006-02, iss. 33, p. 1579, 2006.

    [Abstract]

    Abstract not Available.

    [Bibtex]

    @article{Daniel30062006,
    author = {Daniel, Jurgen and Arias, Ana Claudia and Krusor, Brent and Lujan, Rene and Street, Robert},
    title = {The Road Towards Large-Area Electronics Without Vacuum Tools},
    volume = {MA2006-02},
    number = {33},
    pages = {1579},
    year = {2006},
    abstract ={Abstract not Available.},
    URL = {http://ma.ecsdl.org/content/MA2006-02/33/1579.abstract},
    eprint = {http://ma.ecsdl.org/content/MA2006-02/33/1579.full.pdf+html},
    journal = {Meeting Abstracts}
    }

2005

  • [URL] “Printed Organic Electronics,” in Flexible Flat Panel Displays, John Wiley & Sons, Ltd, 2005, pp. 219-243.

    [Abstract]

    This chapter contains sections titled: * Introduction * System Requirements * Transistor Requirements * Organic Semiconductors * Digital Lithography * Prospects * Acknowledgements * References

    [Bibtex]

    @inbook {apte2005,
    title = {Printed Organic Electronics},
    author = {Apte, Raj B. and Street, Robert A. and Arias, Ana Claudia and Salleo, Alberto and Chabinyc, Michael and Wong, William S. and Ong, Beng S. and Wu, Yiliang and Liu, Ping and Gardner, Sandra},
    author = {},
    publisher = {John Wiley & Sons, Ltd},
    isbn = {9780470870501},
    url = {http://dx.doi.org/10.1002/0470870508.ch12},
    doi = {10.1002/0470870508.ch12},
    pages = {219–243},
    keywords = {organic thin film transistors (OTFTs), poly(dialkylquaterthiophene) (PQT), organic light-emitting diodes (OLEDs), printed organic electronics, contact resistance, bias stress, OTFTs},
    booktitle = {Flexible Flat Panel Displays},
    year = {2005},
    abstract = {This chapter contains sections titled:
    * Introduction
    * System Requirements
    * Transistor Requirements
    * Organic Semiconductors
    * Digital Lithography
    * Prospects
    * Acknowledgements
    * References},
    }
  • [URL] J. H. Daniel, A. C. Arias, W. S. Wong, R. Lujan, B. S. Krusor, R. B. Apte, M. L. Chabinyc, A. Salleo, R. A. Street, N. Chopra, G. Iftime, and P. M. Kazmaier, “54.1: Flexible Electrophoretic Displays with Jet-Printed Active-Matrix Backplanes,” SID Symposium Digest of Technical Papers, vol. 36, iss. 1, pp. 1630-1633, 2005.

    [Abstract]

    We report on the integration of electrophoretic media with flexible backplanes. The active-matrix backplanes are based on amorphous-silicon or on organic-semiconductor technology. Conventional photolithography was fully replaced by jet-printing. Flexible electrophoretic media is fabricated by photolithography and by molding of micro-cell structures. Various aspects will be addressed, concerning the media, the backplanes and the integration.

    [Bibtex]

    @article {SDTP:SDTP4718,
    author = {Daniel, J. H. and Arias, A. C. and Wong, W. S. and Lujan, R. and Krusor, B. S. and Apte, R. B. and Chabinyc, M. L. and Salleo, A. and Street, R. A. and Chopra, N. and Iftime, G. and Kazmaier, P. M.},
    title = {54.1: Flexible Electrophoretic Displays with Jet-Printed Active-Matrix Backplanes},
    journal = {SID Symposium Digest of Technical Papers},
    volume = {36},
    number = {1},
    publisher = {Blackwell Publishing Ltd},
    issn = {2168-0159},
    url = {http://dx.doi.org/10.1889/1.2720336},
    doi = {10.1889/1.2720336},
    pages = {1630–1633},
    year = {2005},
    abstract = {We report on the integration of electrophoretic media with flexible backplanes. The active-matrix backplanes are based on amorphous-silicon or on organic-semiconductor technology. Conventional photolithography was fully replaced by jet-printing. Flexible electrophoretic media is fabricated by photolithography and by molding of micro-cell structures. Various aspects will be addressed, concerning the media, the backplanes and the integration.},
    }
  • [URL] M. L. Chabinyc, W. S. Wong, A. C. Arias, S. Ready, R. A. Lujan, J. H. Daniel, B. Krusor, R. B. Apte, A. Salleo, and R. A. Street, “Printing Methods and Materials for Large-Area Electronic Devices,” Proceedings of the IEEE, vol. 93, iss. 8, pp. 1491-1499, 2005.

    [Bibtex]

    @ARTICLE{1468606,
    author={Chabinyc, M.L. and Wong, W.S. and Arias, A.C. and Ready, S. and Lujan, R.A. and Daniel, J.H. and Krusor, B. and Apte, R.B. and Salleo, A. and Street, R.A.},
    journal={Proceedings of the IEEE}, title={Printing Methods and Materials for Large-Area Electronic Devices},
    year={2005},
    month={aug. },
    volume={93},
    number={8},
    pages={1491 -1499},
    keywords={active matrix thin film transistor fabrication;digital lithography;digital printing methods;electrophoretic media;inkjet printing;large area electronic devices;digital printing;lithography;polymers;printed circuits;resists;thin film transistors;},
    doi={10.1109/JPROC.2005.851492},
    ISSN={0018-9219},}

2004

  • [URL] N. Corcoran, P. K. H. Ho, A. C. Arias, J. D. Mackenzie, R. H. Friend, G. Fichet, and W. T. S. Huck, “Highly-efficient broadband waveguide outcoupling in light-emitting diodes with self-organized polymer blends,” Applied Physics Letters, vol. 85, iss. 14, pp. 2965-2967, 2004.

    [Bibtex]

    @article{corcoran:2965,
    author = {N. Corcoran and P. K. H. Ho and A. C. Arias and J. D. Mackenzie and R. H. Friend and G. Fichet and W. T. S. Huck},
    collaboration = {},
    title = {Highly-efficient broadband waveguide outcoupling in light-emitting diodes with self-organized polymer blends},
    publisher = {AIP},
    year = {2004},
    journal = {Applied Physics Letters},
    volume = {85},
    number = {14},
    pages = {2965-2967},
    keywords = {polymer blends; organic light emitting diodes; optical waveguides; diffraction gratings; phase separation; organic semiconductors; polymer films; surface chemistry},
    url = {http://link.aip.org/link/?APL/85/2965/1},
    doi = {10.1063/1.1801680}
    }
  • [URL] A. C. Arias, S. E. Ready, R. Lujan, W. S. Wong, K. E. Paul, A. Salleo, M. L. Chabinyc, R. Apte, R. A. Street, Y. Wu, P. Liu, and B. Ong, “All jet-printed polymer thin-film transistor active-matrix backplanes,” Applied Physics Letters, vol. 85, iss. 15, pp. 3304-3306, 2004.

    [Bibtex]

    @article{arias:3304,
    author = {A. C. Arias and S. E. Ready and R. Lujan and W. S. Wong and K. E. Paul and A. Salleo and M. L. Chabinyc and R. Apte and Robert A. Street and Y. Wu and P. Liu and B. Ong},
    collaboration = {},
    title = {All jet-printed polymer thin-film transistor active-matrix backplanes},
    publisher = {AIP},
    year = {2004},
    journal = {Applied Physics Letters},
    volume = {85},
    number = {15},
    pages = {3304-3306},
    keywords = {polymer films; flat panel displays; organic semiconductors; thin film transistors; carrier mobility; polymer structure},
    url = {http://link.aip.org/link/?APL/85/3304/1},
    doi = {10.1063/1.1801673}
    }
  • [URL] G. Fichet, N. Corcoran, P.  K.  H. Ho, A.  C. Arias, J.  D. MacKenzie, W.  T.  S. Huck, and R.  H. Friend, “Self-Organized Photonic Structures in Polymer Light-Emitting Diodes,” Advanced Materials, vol. 16, iss. 21, pp. 1908-1912, 2004.

    [Bibtex]

    @article {ADMA:ADMA200400316,
    author = {Fichet, G. and Corcoran, N. and Ho, P. K. H. and Arias, A. C. and MacKenzie, J. D. and Huck, W. T. S. and Friend, R. H.},
    title = {Self-Organized Photonic Structures in Polymer Light-Emitting Diodes},
    journal = {Advanced Materials},
    volume = {16},
    number = {21},
    publisher = {WILEY-VCH Verlag},
    issn = {1521-4095},
    url = {http://dx.doi.org/10.1002/adma.200400316},
    doi = {10.1002/adma.200400316},
    pages = {1908–1912},
    keywords = {Light emitting diodes, organic, Photonic crystals, Thin films, polymers},
    year = {2004},
    }

2003

  • [URL] N. Corcoran, A. C. Arias, J. S. Kim, J. D. MacKenzie, and R. H. Friend, “Increased efficiency in vertically segregated thin-film conjugated polymer blends for light-emitting diodes,” Applied Physics Letters, vol. 82, iss. 2, pp. 299-301, 2003.

    [Bibtex]

    @article{corcoran:299,
    author = {N. Corcoran and A. C. Arias and J. S. Kim and J. D. MacKenzie and R. H. Friend},
    collaboration = {},
    title = {Increased efficiency in vertically segregated thin-film conjugated polymer blends for light-emitting diodes},
    publisher = {AIP},
    year = {2003},
    journal = {Applied Physics Letters},
    volume = {82},
    number = {2},
    pages = {299-301},
    keywords = {segregation; conducting polymers; organic semiconductors; polymer blends; light emitting diodes; semiconductor device measurement; polymer films},
    url = {http://link.aip.org/link/?APL/82/299/1},
    doi = {10.1063/1.1537049}
    }
  • L. S. Roman, A. C. Arias, M. Theander, M. R. Andersson, and O. InganÃtextcurrencys, “Photovoltaic devices based on photo induced charge transfer in polythiophene: CN-PPV blends,” Brazilian Journal of Physics, vol. 33, pp. 376-381, 2003.

    [Bibtex]

    @article{ROMAN2003,
    title = {{Photovoltaic devices based on photo induced charge transfer in polythiophene: CN-PPV blends}},
    journal = {{Brazilian Journal of Physics}},
    author={Roman, L. S. AND Arias, A. C. AND Theander, M. AND Andersson, M. R. AND Ingan\~A\textcurrencys, O.},
    ISSN = {0103-9733},
    language = {en},
    URL = {http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-97332003000200041&nrm=iso},
    volume = {33},
    year = {2003},
    month = {06},
    pages = {376 – 381},
    publisher = {scielo},
    crossref = {10.1590/S0103-97332003000200041},
    }
  • [URL] H. Sirringhaus, S. E. Burns, C. Kuhn, K. Jacobs, J. D. MacKenzie, M. Etchells, K. Chalmers, P. Devine, N. Murton, N. Stone, D. Wilson, P. Cain, T. Brown, A. C. Asais, J. Mills, and R. H. Friend, “34.1: Active Matrix Displays Made with Printed Polymer Thin Film Transistors,” SID Symposium Digest of Technical Papers, vol. 34, iss. 1, pp. 1084-1087, 2003.

    [Abstract]

    We present a process for active matrix flat panel display manufacture by printing polymer thin film transistors. In this process, transistors are fabricated using soluble semi-conducting and conducting materials. Accurate definition of the transistor channel and other circuit components is achieved by direct inkjet printing combined with surface energy patterning. We have used this process to create a 4,800 pixel, 50 dpi, active matrix display. This process is in principle environmentally friendly, low temperature, compatible with flexible substrates, cost effective and advantageous for short run length and large display sizes.

    [Bibtex]

    @article {SDTP:SDTP4233,
    author = {Sirringhaus, H. and Burns, S. E. and Kuhn, C. and Jacobs, K. and MacKenzie, J. D. and Etchells, M. and Chalmers, K. and Devine, P. and Murton, N. and Stone, N. and Wilson, D. and Cain, P. and Brown, T. and Asais, A. C. and Mills, J. and Friend, R. H.},
    title = {34.1: Active Matrix Displays Made with Printed Polymer Thin Film Transistors},
    journal = {SID Symposium Digest of Technical Papers},
    volume = {34},
    number = {1},
    publisher = {Blackwell Publishing Ltd},
    issn = {2168-0159},
    url = {http://dx.doi.org/10.1889/1.1832476},
    doi = {10.1889/1.1832476},
    pages = {1084–1087},
    year = {2003},
    abstract = {We present a process for active matrix flat panel display manufacture by printing polymer thin film transistors. In this process, transistors are fabricated using soluble semi-conducting and conducting materials. Accurate definition of the transistor channel and other circuit components is achieved by direct inkjet printing combined with surface energy patterning. We have used this process to create a 4,800 pixel, 50 dpi, active matrix display. This process is in principle environmentally friendly, low temperature, compatible with flexible substrates, cost effective and advantageous for short run length and large display sizes.},
    }
  • [URL] D. J. Brennan, P. H. Townsend III, D. M. Welsh, M. G. Dibbs, J. M. Shaw, J. L. Miklovich, R. B. Boeke, A. C. Arias, L. Creswell, J. D. MacKenzie, C. Ramsdale, A. Menon, and H. Sirringhaus, “Polyfluorenes as organic semiconductors for polymeric field effect transistors,” , pp. 1-6, 2003.

    [Bibtex]

    @article{doi:10.1117/12.505749,
    author = {Brennan, David J. and Townsend III, Paul H. and Welsh, Dean M. and Dibbs, Mitchell G. and Shaw, Jeff M. and Miklovich, Jessica L. and Boeke, Robyn B. and Arias, Ana Claudia and Creswell, Lisa and MacKenzie, J. D. and Ramsdale, Catherine and Menon, Anoop and Sirringhaus, Henning},
    title = {Polyfluorenes as organic semiconductors for polymeric field effect transistors},
    volume = {},
    number = {},
    pages = {1-6},
    year = {2003},
    doi = {10.1117/12.505749},
    URL = { + http://dx.doi.org/10.1117/12.505749},
    eprint = {}
    }

2002

  • [URL] C. M. Ramsdale, I. C. Bache, J. D. MacKenzie, D. S. Thomas, A. C. Arias, A. M. Donald, R. H. Friend, and N. C. Greenham, “ESEM imaging of polyfluorene blend cross-sections for organic devices,” Physica E: Low-dimensional Systems and Nanostructures, vol. 14, iss. 1–2, pp. 268-271, 2002.

    [Abstract]

    We report the use of environmental scanning electron microscopy (ESEM) to determine the phase separation in the cross-section of a 200 nm thick polyfluorene blend film, of the type used in polymer photovoltaic devices and LEDs. The micron and sub-micron surface phases are found to penetrate through the film to the underlying substrate, whilst smaller surface features do not necessarily propagate through the film. The observed cross-sectional structure helps to explain the optoelectronic response of these blends and shows that ESEM is an effective tool in the characterisation of polymer blend cross-sections.

    [Bibtex]

    @article{Ramsdale2002268,
    title = "ESEM imaging of polyfluorene blend cross-sections for organic devices",
    journal = "Physica E: Low-dimensional Systems and Nanostructures",
    volume = "14",
    number = "1–2",
    pages = "268 – 271",
    year = "2002",
    note = "",
    issn = "1386-9477",
    doi = "10.1016/S1386-9477(02)00392-2",
    url = "http://www.sciencedirect.com/science/article/pii/S1386947702003922",
    author = "C.M Ramsdale and I.C Bache and J.D MacKenzie and D.S Thomas and A.C Arias and A.M Donald and R.H Friend and N.C Greenham",
    keywords = "ESEM",
    keywords = "Conjugated polymer",
    keywords = "Cross-section",
    keywords = "Organic devices",
    keywords = "Solar cells",
    abstract = "We report the use of environmental scanning electron microscopy (ESEM) to determine the phase separation in the cross-section of a 200 nm thick polyfluorene blend film, of the type used in polymer photovoltaic devices and LEDs. The micron and sub-micron surface phases are found to penetrate through the film to the underlying substrate, whilst smaller surface features do not necessarily propagate through the film. The observed cross-sectional structure helps to explain the optoelectronic response of these blends and shows that ESEM is an effective tool in the characterisation of polymer blend cross-sections."
    }
  • [URL] D. M. Russell, A. C. Arias, R. H. Friend, C. Silva, C. Ego, A. C. Grimsdale, and K. Mullen, “Efficient light harvesting in a photovoltaic diode composed of a semiconductor conjugated copolymer blend,” Applied Physics Letters, vol. 80, iss. 12, pp. 2204-2206, 2002.

    [Bibtex]

    @article{russell:2204,
    author = {David M. Russell and Ana C. Arias and Richard H. Friend and Carlos Silva and Christophe Ego and Andrew C. Grimsdale and Klaus Mullen},
    collaboration = {},
    title = {Efficient light harvesting in a photovoltaic diode composed of a semiconductor conjugated copolymer blend},
    publisher = {AIP},
    year = {2002},
    journal = {Applied Physics Letters},
    volume = {80},
    number = {12},
    pages = {2204-2206},
    keywords = {conducting polymers; organic semiconductors; polymer blends; dyes; photovoltaic effects; polarons; radiative lifetimes; photodiodes},
    url = {http://link.aip.org/link/?APL/80/2204/1},
    doi = {10.1063/1.1464226}
    }
  • [URL] C. M. Ramsdale, J. A. Barker, A. C. Arias, J. D. MacKenzie, R. H. Friend, and N. C. Greenham, “The origin of the open-circuit voltage in polyfluorene-based photovoltaic devices,” Journal of Applied Physics, vol. 92, iss. 8, pp. 4266-4270, 2002.

    [Bibtex]

    @article{ramsdale:4266,
    author = {C. M. Ramsdale and J. A. Barker and A. C. Arias and J. D. MacKenzie and R. H. Friend and N. C. Greenham},
    collaboration = {},
    title = {The origin of the open-circuit voltage in polyfluorene-based photovoltaic devices},
    publisher = {AIP},
    year = {2002},
    journal = {Journal of Applied Physics},
    volume = {92},
    number = {8},
    pages = {4266-4270},
    keywords = {polymer films; photoelectric devices; work function},
    url = {http://link.aip.org/link/?JAP/92/4266/1},
    doi = {10.1063/1.1506385}
    }
  • [URL] H. J. Snaith, A. C. Arias, A. C. Morteani, C. Silva, and R. H. Friend, “Charge Generation Kinetics and Transport Mechanisms in Blended Polyfluorene Photovoltaic Devices,” Nano Letters, vol. 2, iss. 12, pp. 1353-1357, 2002.

    [Bibtex]

    @article{doi:10.1021/nl0257418,
    author = {Snaith, Henry J. and Arias, Ana C. and Morteani, Arne C. and Silva, Carlos and Friend, Richard H.},
    title = {Charge Generation Kinetics and Transport Mechanisms in Blended Polyfluorene Photovoltaic Devices},
    journal = {Nano Letters},
    volume = {2},
    number = {12},
    pages = {1353-1357},
    year = {2002},
    doi = {10.1021/nl0257418},
    URL = {http://pubs.acs.org/doi/abs/10.1021/nl0257418},
    eprint = {http://pubs.acs.org/doi/pdf/10.1021/nl0257418}
    }
  • [URL] S. Burns, C. Kuhn, N. Stone, D. Wilson, A. C. Arias, T. Brown, P. Cain, P. Devine, K. Jacobs, N. Murton, J. D. MacKenzie, J. Mills, and H. Sirringhaus, “43.1: Invited Paper: Inkjet Printed Polymer Thin Film Transistors for Active-Matrix Display Applications,” SID Symposium Digest of Technical Papers, vol. 33, iss. 1, pp. 1193-1195, 2002.

    [Abstract]

    We have recently demonstrated fabrication of polymer thin film transistor (TFT) circuits by a combination of solution self-assembly and direct inkjet printing. Control over the morphology of the polymer semiconductor and uniaxial alignment of polymer chains parallel to the direction of current flow in the device is obtained by making use of polymer self-organisation. Accurate definition of the transistor channel and other circuit components is achieved by direct inkjet printing combined with surface energy patterning. Here we discuss the application of this novel manufacturing process for polymer TFTs to active matrix displays. We will focus on advantages and disadvantages of polymer TFT technology compared with conventional thin film silicon devices.

    [Bibtex]

    @article {SDTP:SDTP3922,
    author = {Burns, S. and Kuhn, C. and Stone, N. and Wilson, D. and Arias, A. C. and Brown, T. and Cain, P. and Devine, P. and Jacobs, K. and Murton, N. and MacKenzie, J. D. and Mills, J. and Sirringhaus, H.},
    title = {43.1: Invited Paper: Inkjet Printed Polymer Thin Film Transistors for Active-Matrix Display Applications},
    journal = {SID Symposium Digest of Technical Papers},
    volume = {33},
    number = {1},
    publisher = {Blackwell Publishing Ltd},
    issn = {2168-0159},
    url = {http://dx.doi.org/10.1889/1.1830158},
    doi = {10.1889/1.1830158},
    pages = {1193–1195},
    year = {2002},
    abstract = {We have recently demonstrated fabrication of polymer thin film transistor (TFT) circuits by a combination of solution self-assembly and direct inkjet printing. Control over the morphology of the polymer semiconductor and uniaxial alignment of polymer chains parallel to the direction of current flow in the device is obtained by making use of polymer self-organisation. Accurate definition of the transistor channel and other circuit components is achieved by direct inkjet printing combined with surface energy patterning. Here we discuss the application of this novel manufacturing process for polymer TFTs to active matrix displays. We will focus on advantages and disadvantages of polymer TFT technology compared with conventional thin film silicon devices.},
    }
  • [URL] A. C. Arias, N. Corcoran, M. Banach, R. H. Friend, J. D. MacKenzie, and W. T. S. Huck, “Vertically segregated polymer-blend photovoltaic thin-film structures through surface-mediated solution processing,” Applied Physics Letters, vol. 80, iss. 10, pp. 1695-1697, 2002.

    [Bibtex]

    @article{arias:1695,
    author = {A. C. Arias and N. Corcoran and M. Banach and R. H. Friend and J. D. MacKenzie and W. T. S. Huck},
    collaboration = {},
    title = {Vertically segregated polymer-blend photovoltaic thin-film structures through surface-mediated solution processing},
    publisher = {AIP},
    year = {2002},
    journal = {Applied Physics Letters},
    volume = {80},
    number = {10},
    pages = {1695-1697},
    keywords = {polymer blends; polymer films; liquid phase deposited coatings; semiconductor thin films; organic semiconductors; surface treatment; evaporation; surface segregation; photoelectric devices; surface energy; self-assembly; monolayers; semiconductor growth},
    url = {http://link.aip.org/link/?APL/80/1695/1},
    doi = {10.1063/1.1456550}
    }
  • C. Silva, D. M. Russell, A. S. Dhoot, L. M. Herz, C. Daniel, N. C. Greenham, A. C Arias, S. Setayesh, K. Müllen, and R. H. Friend, “Exciton and polaron dynamics in a step-ladder polymeric semiconductor: the influence of interchain order,” Journal of Physics: Condensed Matter, vol. 14, iss. 42, p. 9803, 2002.

    [Bibtex]

    @article{0953-8984-14-42-302,
    author={Carlos Silva and David M Russell and Anoop S Dhoot and Laura M Herz and Clément Daniel and Neil C Greenham and Ana C
    Arias and Sepas Setayesh and Klaus Müllen and Richard H Friend},
    title={Exciton and polaron dynamics in a step-ladder polymeric semiconductor: the influence of interchain order},
    journal={Journal of Physics: Condensed Matter},
    volume={14},
    number={42},
    pages={9803},
    url={http://stacks.iop.org/0953-8984/14/i=42/a=302},
    year={2002}
    }
  • [URL] R. G. Milner, A. C. Arias, R. Stevenson, J. D. Mackenzie, D. Richards, R. H. Friend, D. -J. Kang, and M. Blamire, “Phase separation in polyfluorene blends investigated with complementary scanning probe microscopies,” Materials Science and Technology, vol. 18, iss. 7, pp. 759-762, 2002.

    [Bibtex]

    @article {Milner:2002-07-01T00:00:00:0267-0836:759,
    author = "Milner, R. G. and Arias, A. C. and Stevenson, R. and Mackenzie, J. D. and Richards, D. and Friend, R. H. and Kang, D.-J. and Blamire, M.",
    title = "Phase separation in polyfluorene blends investigated with complementary scanning probe microscopies",
    journal = "Materials Science and Technology",
    volume = "18",
    number = "7",
    year = "2002",
    pages = "759-762",
    url = "http://www.ingentaconnect.com/content/maney/mst/2002/00000018/00000007/art00012",
    doi = "doi:10.1179/026708302225003910"
    }

2001

  • [URL] A. C. Arias, J. D. MacKenzie, R. Stevenson, J. J. M. Halls, M. Inbasekaran, E. P. Woo, D. Richards, and R. H. Friend, “Photovoltaic Performance and Morphology of Polyfluorene Blends:  A Combined Microscopic and Photovoltaic Investigation,” Macromolecules, vol. 34, iss. 17, pp. 6005-6013, 2001.

    [Bibtex]

    @article{doi:10.1021/ma010240e,
    author = {Arias, A. C. and MacKenzie, J. D. and Stevenson, R. and Halls, J. J. M. and Inbasekaran, M. and Woo, E. P. and Richards, D. and Friend, R. H.},
    title = {Photovoltaic Performance and Morphology of Polyfluorene Blends:  A Combined Microscopic and Photovoltaic Investigation},
    journal = {Macromolecules},
    volume = {34},
    number = {17},
    pages = {6005-6013},
    year = {2001},
    doi = {10.1021/ma010240e},
    URL = {http://pubs.acs.org/doi/abs/10.1021/ma010240e},
    eprint = {http://pubs.acs.org/doi/pdf/10.1021/ma010240e}
    }
  • [URL] R. Stevenson, A. C. Arias, C. Ramsdale, J. D. MacKenzie, and D. Richards, “Raman microscopy determination of phase composition in polyfluorene composites,” Applied Physics Letters, vol. 79, iss. 14, pp. 2178-2180, 2001.

    [Bibtex]

    @article{stevenson:2178,
    author = {R. Stevenson and A. C. Arias and C. Ramsdale and J. D. MacKenzie and D. Richards},
    collaboration = {},
    title = {Raman microscopy determination of phase composition in polyfluorene composites},
    publisher = {AIP},
    year = {2001},
    journal = {Applied Physics Letters},
    volume = {79},
    number = {14},
    pages = {2178-2180},
    keywords = {polymer blends; Raman spectra; optical microscopy; phase separation; excitons; optical polymers},
    url = {http://link.aip.org/link/?APL/79/2178/1},
    doi = {10.1063/1.1407863}
    }
  • [URL] C. Silva, A. S. Dhoot, D. M. Russell, M. A. Stevens, A. C. Arias, D. J. MacKenzie, N. C. Greenham, R. H. Friend, S. Setayesh, and K. Müllen, “Efficient exciton dissociation via two-step photoexcitation in polymeric semiconductors,” Phys. Rev. B, vol. 64, p. 125211, 2001.

    [Bibtex]

    @article{PhysRevB.64.125211,
    title = {Efficient exciton dissociation via two-step photoexcitation in polymeric semiconductors},
    author = {Silva, Carlos and Dhoot, Anoop S. and Russell, David M. and Stevens, Mark A. and Arias, Ana C. and MacKenzie, J. Devin and Greenham, Neil C. and Friend, Richard H. and Setayesh, Sepas and M\"ullen, Klaus},
    journal = {Phys. Rev. B},
    volume = {64},
    issue = {12},
    pages = {125211},
    numpages = {7},
    year = {2001},
    month = {Sep},
    doi = {10.1103/PhysRevB.64.125211},
    url = {http://link.aps.org/doi/10.1103/PhysRevB.64.125211},
    publisher = {American Physical Society}
    }
  • [URL] R. Stevenson, R. G. Milner, D. Richards, A. C. Arias, J. D. Mackenzie, J. J. M. Halls, R. H. Friend, D. -J. Kang, and M. Blamire, “Fluorescence scanning near-field optical microscopy of polyfluorene composites,” Journal of Microscopy, vol. 202, iss. 2, pp. 433-438, 2001.

    [Bibtex]

    @article {JMI:JMI871,
    author = {Stevenson, R. and Milner, R. G. and Richards, D. and Arias, A. C. and Mackenzie, J. D. and Halls, J. J. M. and Friend, R. H. and Kang, D.-J. and Blamire, M.},
    title = {Fluorescence scanning near-field optical microscopy of polyfluorene composites},
    journal = {Journal of Microscopy},
    volume = {202},
    number = {2},
    publisher = {Blackwell Science Ltd},
    issn = {1365-2818},
    url = {http://dx.doi.org/10.1046/j.1365-2818.2001.00871.x},
    doi = {10.1046/j.1365-2818.2001.00871.x},
    pages = {433–438},
    keywords = {charge transfer, conjugated polymers, morphology, nanostructures, phase separation, photovoltaic devices, SNOM},
    year = {2001}
    }

2000

  • [URL] J. J. M. Halls, A. C. Arias, J. D. MacKenzie, W. Wu, M. Inbasekaran, E. P. Woo, and R. H. Friend, “Photodiodes Based on Polyfluorene Composites: Influence of Morphology,” Advanced Materials, vol. 12, iss. 7, pp. 498-502, 2000.

    [Bibtex]

    @article {ADMA:ADMA498,
    author = {Halls, J. J. M. and Arias, A. C. and MacKenzie, J. D. and Wu, W. and Inbasekaran, M. and Woo, E. P. and Friend, R. H.},
    title = {Photodiodes Based on Polyfluorene Composites: Influence of Morphology},
    journal = {Advanced Materials},
    volume = {12},
    number = {7},
    publisher = {WILEY-VCH Verlag GmbH},
    issn = {1521-4095},
    url = {http://dx.doi.org/10.1002/(SICI)1521-4095(200004)12:7<498::AID-ADMA498>3.0.CO;2-H},
    doi = {10.1002/(SICI)1521-4095(200004)12:7<498::AID-ADMA498>3.0.CO;2-H},
    pages = {498–502},
    keywords = {Composite materials, Conjugated polymers, Photodiodes, Photovoltaic cells, Polyfluorenes, Semiconductors},
    year = {2000},
    }
  • [URL] A. C. Arias, L. S. Roman, T. Kugler, R. Toniolo, M. S. Meruvia, and I. A. Hümmelgen, “The use of tin oxide thin films as a transparent electrode in PPV based light-emitting diodes,” Thin Solid Films, vol. 371, iss. 1–2, pp. 201-206, 2000.

    [Bibtex]

    @article{Arias2000201,
    title = "The use of tin oxide thin films as a transparent electrode in PPV based light-emitting diodes",
    journal = "Thin Solid Films",
    volume = "371",
    number = "1–2",
    pages = "201 – 206",
    year = "2000",
    note = "",
    issn = "0040-6090",
    doi = "10.1016/S0040-6090(00)00967-6",
    url = "http://www.sciencedirect.com/science/article/pii/S0040609000009676",
    author = "A.C Arias and L.S Roman and T Kugler and R Toniolo and M.S Meruvia and I.A Hümmelgen",
    keywords = "Chemical vapour deposition",
    keywords = "Electroluminescence",
    keywords = "Stability",
    keywords = "Tin oxide",
    keywords = "Poly(<span style=’font-style: italic’>p</span>-phenylene vinylene)",
    keywords = "Light-emitting diodes"
    }

1999

  • [URL] M. Granström, K. Petritsch, A. C. Arias, and R. H. Friend, “High efficiency polymer photodiodes,” Synthetic Metals, vol. 102, iss. 1–3, pp. 957-958, 1999.

    [Bibtex]

    @article{Granström1999957,
    title = "High efficiency polymer photodiodes",
    journal = "Synthetic Metals",
    volume = "102",
    number = "1–3",
    pages = "957 – 958",
    year = "1999",
    note = "",
    issn = "0379-6779",
    doi = "10.1016/S0379-6779(98)00993-X",
    url = "http://www.sciencedirect.com/science/article/pii/S037967799800993X",
    author = "Magnus Granström and Klaus Petritsch and Ana Claudia Arias and Richard H. Friend",
    keywords = "Poly(phenylene vinylene) and derivatives",
    keywords = "Polythiophene and derivatives",
    keywords = "Solar cells",
    keywords = "Interface preparation"
    }
  • [URL] A. C. Arias, M. Granström, K. Petritsch, and R. H. Friend, “Organic Photodiodes using Polymeric Anodes,” Synthetic Metals, vol. 102, iss. 1–3, pp. 953-954, 1999.

    [Bibtex]

    @article{Arias1999953,
    title = "Organic Photodiodes using Polymeric Anodes",
    journal = "Synthetic Metals",
    volume = "102",
    number = "1–3",
    pages = "953 – 954",
    year = "1999",
    note = "",
    issn = "0379-6779",
    doi = "10.1016/S0379-6779(98)00976-X",
    url = "http://www.sciencedirect.com/science/article/pii/S037967799800976X",
    author = "A.C. Arias and M. Granström and K. Petritsch and R.H. Friend",
    keywords = "photodiodes",
    keywords = "poly (<span style=’font-style: italic’>p</span>-phenylenevinylene) and poly (3,4 ethylenedioxythiophene)"
    }
  • [URL] A. C. Arias, M. Granström, D. S. Thomas, K. Petritsch, and R. H. Friend, “Doped conducting-polymer\char21semiconducting-polymer interfaces: Their use in organic photovoltaic devices,” Phys. Rev. B, vol. 60, pp. 1854-1860, 1999.

    [Bibtex]

    @article{PhysRevB.60.1854,
    title = {Doped conducting-polymer\char21{}semiconducting-polymer interfaces: Their use in organic photovoltaic devices},
    author = {Arias, A. C. and Granstr\"om, M. and Thomas, D. S. and Petritsch, K. and Friend, R. H.},
    journal = {Phys. Rev. B},
    volume = {60},
    issue = {3},
    pages = {1854–1860},
    year = {1999},
    month = {Jul},
    doi = {10.1103/PhysRevB.60.1854},
    url = {http://link.aps.org/doi/10.1103/PhysRevB.60.1854},
    publisher = {American Physical Society}
    }

1998

  • [URL] A. C. Arias, J. R. de Lima, and I. A. Hümmelgen, “Tin Oxide as a Cathode in Organic Light-Emitting Diodes,” Advanced Materials, vol. 10, iss. 5, pp. 392-394, 1998.

    [Bibtex]

    @article {ADMA:ADMA392,
    author = {Arias, Ana C. and de Lima, Joaquim R. and Hümmelgen, Ivo A.},
    title = {Tin Oxide as a Cathode in Organic Light-Emitting Diodes},
    journal = {Advanced Materials},
    volume = {10},
    number = {5},
    publisher = {WILEY-VCH Verlag GmbH},
    issn = {1521-4095},
    url = {http://dx.doi.org/10.1002/(SICI)1521-4095(199803)10:5<392::AID-ADMA392>3.0.CO;2-U},
    doi = {10.1002/(SICI)1521-4095(199803)10:5<392::AID-ADMA392>3.0.CO;2-U},
    pages = {392–394},
    year = {1998},
    }
  • [URL] M. Granstrom, K. Petritsch, A. C. Arias, A. Lux, M. R. Andersson, and R. H. Friend, “Laminated fabrication of polymeric photovoltaic diodes,” Nature, vol. 395, iss. 6699, pp. 257-260, 1998.

    [Bibtex]

    @article {Granstrom1998,
    author = {M. Granstrom and K. Petritsch and A. C. Arias and A. Lux and M. R. Andersson and R. H. Friend},
    title = {Laminated fabrication of polymeric photovoltaic diodes},
    journal = {Nature},
    volume = {395},
    number = {6699},
    url = {http://dx.doi.org/10.1038/26183},
    doi = {10.1038/26183},
    pages = {257-260},
    year = {1998},
    }

1997

  • [URL] Y. P. Yadava, G. Denicoló, A. C. Arias, L. S. Roman, and I. A. Hümmelgen, “Preparation and characterization of transparent conducting tin oxide thin film electrodes by chemical vapour deposition from reactive thermal evaporation of SnCl2,” Materials Chemistry and Physics, vol. 48, iss. 3, pp. 263-267, 1997.

    [Bibtex]

    @article{Yadava1997263,
    title = "Preparation and characterization of transparent conducting tin oxide thin film electrodes by chemical vapour deposition from reactive thermal evaporation of SnCl2",
    journal = "Materials Chemistry and Physics",
    volume = "48",
    number = "3",
    pages = "263 – 267",
    year = "1997",
    note = "",
    issn = "0254-0584",
    doi = "10.1016/S0254-0584(96)01899-8",
    url = "http://www.sciencedirect.com/science/article/pii/S0254058496018998",
    author = "Y.P Yadava and G Denicoló and A.C Arias and L.S Roman and I.A Hümmelgen",
    keywords = "Tin oxide",
    keywords = "Thin films chemical vapour deposition",
    keywords = "Structure",
    keywords = "Optical transmittance",
    keywords = "Electrical properties",
    keywords = "Surface morphology"
    }
  • [URL] A. C. Arias, I. A. Hümmelgen, A. Meneguzzi, and C. A. Ferreira, “A conjugated polymer-based voltage-regulator device,” Advanced Materials, vol. 9, iss. 12, pp. 972-974, 1997.

    [Bibtex]

    @article {ADMA:ADMA19970091209,
    author = {Arias, Ana C. and Hümmelgen, Ivo A. and Meneguzzi, Alvaro and Ferreira, Carlos A.},
    title = {A conjugated polymer-based voltage-regulator device},
    journal = {Advanced Materials},
    volume = {9},
    number = {12},
    publisher = {WILEY-VCH Verlag GmbH},
    issn = {1521-4095},
    url = {http://dx.doi.org/10.1002/adma.19970091209},
    doi = {10.1002/adma.19970091209},
    pages = {972–974},
    year = {1997},
    }

1996

  • L. S. Roman, Y. P. Yadava, G. Denicoló, A. C. Arias, and I. A. Hümmelgen, “Time-dependent structural modifications in tin oxide thin films under environmental conditions,” Journal of Materials Science: Materials in Electronics, vol. 7, pp. 423-426, 1996.
    10.1007/BF00180780
    [Bibtex]
    @article {springerlink:10.1007/BF00180780,
    author = {Roman, L. S. and Yadava, Y. P. and Denicoló, G. and Arias, A. C. and Hümmelgen, I. A.},
    title = {Time-dependent structural modifications in tin oxide thin films under environmental conditions},
    journal = {Journal of Materials Science: Materials in Electronics},
    publisher = {Springer New York},
    issn = {0957-4522},
    keyword = {Chemistry and Materials Science},
    pages = {423-426},
    volume = {7},
    issue = {6},
    url = {http://dx.doi.org/10.1007/BF00180780},
    note = {10.1007/BF00180780},
    year = {1996}
    }
  • I. Hümmelgen, Y. Yadava, L. Roman, A. Arias, M. Fernandes, and F. Nart, “Tin oxide as a transparent electrode material for light-emitting diodes fabricated with poly (&lt;i&gt;p&lt;/i&gt;-phenylene vinylene),” Bulletin of Materials Science, vol. 19, pp. 423-427, 1996.
    10.1007/BF02744679
    [Bibtex]
    @article {springerlink:10.1007/BF02744679,
    author = {Hümmelgen, I and Yadava, Y and Roman, L and Arias, A and Fernandes, M and Nart, F},
    affiliation = {Universidade Federal do Paraná Departamento de Física Cx. Postal 19081 81531-990 Curitiba PR Brasil},
    title = {Tin oxide as a transparent electrode material for light-emitting diodes fabricated with poly (&lt;i&gt;p&lt;/i&gt;-phenylene vinylene)},
    journal = {Bulletin of Materials Science},
    publisher = {Springer India, in co-publication with Indian Academy of Sciences},
    issn = {0250-4707},
    keyword = {Chemistry and Materials Science},
    pages = {423-427},
    volume = {19},
    issue = {2},
    url = {http://dx.doi.org/10.1007/BF02744679},
    note = {10.1007/BF02744679},
    year = {1996}
    }