Barry O'Brien

Low-temperature amorphous-silicon backplane technology development for flexible displays in a manufacturing pilot-line environment

— A low-temperature amorphous-silicon (a-Si:H) thin-film-transistor (TFT) backplane technology for high-information-content flexible displays has been developed. Backplanes were integrated with frontplane technologies to produce high-performance active-matrix reflective electrophoretic ink, reflective cholesteric liquid crystal and emissive OLED flexible-display technology demonstrators (TDs). Backplanes up to 4 in. on the diagonal have been fabricated on a 6-in. wafer-scale pilot line. The critical steps in the evolution of backplane technology, from qualification of baseline low-temperature (180°C) a-Si:H process on the 6-in. line with rigid substrates, to transferring the process to flexible plastic and flexible stainless-steel substrates, to form factor scale-up of the TFT arrays, and finally manufacturing scale-up to a Gen 2 (370 × 470 mm) display-scale pilot line, will be reviewed.

Application of Flexible OLED Display Technology for Electro-Optical Stimulation and/or Silencing of Neural Activity

This paper presents a new biophotonic application for large-area, high-resolution, flexible organic light-emitting diode (OLED) display technology currently used to manufacture low-cost color flexible displays on plastic substrates. The new concept uses a fully addressable high resolution flexible OLED pixel array on a thin, mechanically compliant biocompatible plastic substrate to selectively stimulate and/or silence small groups of neurons on either the cortical surface or, alternatively, within the deep brain. Optical measurements from a 455 nm blue flexible OLED test structure demonstrated the ability to emit 1 mW/mm2 of instantaneous light intensity using a 13 V, 20 Hz pulse, which meets the minimum reported intensity at ~ 450 nm to induce optical stimulation in genetically modified neural tissue. Biocompatibility was successfully demonstrated by the ability to grow human epithelial cells on the surface of a full TFT process flow plastic flexible display substrate. Additionally, a new active matrix array display architecture was designed to support pulsed mode OLED operation. These preliminary results demonstrate the initial viability of extending flexible plastic substrate OLED display technology to the development of large-area, high-resolution emissive active matrix arrays for chronic optogenetic applications.

30.2: Active Matrix Electrophoretic Displays on Temporary Bonded Stainless Steel Substrates with 180 °C a‐Si:H TFTs

A low temperature, 180 °C, amorphous Si (a-Si:H) process on bonded stainless steel substrates is discussed and a 3.8-inch QVGA active matrix (AM) electrophoretic display as well as a 64×64 electrophoretic display with integrated column drivers are demonstrated. The n-channel thin-film transistors (TFTs) exhibited saturation mobilities of 0.7 cm2/V-sec, median drive currents of 26.2 μA and low defectivity.

Application of Flexible OLED Display Technology to Point-of-Care Medical Diagnostic Testing

This paper presents a new concept combining flexible organic light-emitting diode (OLED) display technology with fluorescent biorecognition microarray technology to fabricate point-of-care immunobiosensors. Our approach is designed to leverage commercial OLED display technology to reduce pre-functionalized biosensor substrate costs to pennies per cm2 combined with leveraging the display industries ability to manufacture an immense number of low-cost consumer electronic products annually. For this work, we demonstrate that our new approach using high brightness flexible OLED display technology combined with a charge integrating readout circuit and optical filters can offer point-of-care diagnostic sensitivity at or below 10 pg/mL, which approaches the lower limit of detection (LLOD) of typical clinical laboratory instrumentation.

White organic light emitting diodes using Pt-based red, green, and blue phosphorescent dopants

Organic light emitting diodes using Pt-based red, green and blue dopants have been built for application to solid state lighting. All layers were deposited by thermal evaporation. Devices used a stacked design with separate red, green and blue layers. Blue devices achieved external quantum efficiencies of over 16% while devices with red / green / blue emissive layers reached quantum efficiencies of up to 15%, depending on the thickness of the red and green layers. We demonstrate an all-Pt based multiple emissive layer WOLED device.

External quantum efficiency enhancement in organic photovoltaic devices employing dual organic anode interfacial layers

We demonstrate the use of a dual anode interfacial layer of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and tetracene for efficient small molecule organic solar cells. These layers provided a multifaceted improvement on device performance by enhancing absorption in the donor layer, serving as an exciton blocking layer at the anode interface, providing a low resistance anode contact, and serving as a templating layer for increased crystallinity in the donor layer. Palladium phthalocyanine/C60 planar heterojunction devices fabricated on top of the dual layers of PEDOT:PSS and tetracene demonstrates 85% enhancement in the donor contribution to external quantum efficiency and yielded a maximum power conversion efficiency of 3.66%.

Flexible reflective and emissive display integration and manufacturing

The U.S. Army, Arizona State University (ASU) and commercial industry have joined forces to create the Flexible Display Center (FDC) at Arizona State University, a large-scale collaborative venture designed to rapidly advance flexible display technology to the brink of commercialization. The Center has completed its startup phase and is now engaged in an intensive and aggressive applied research and development program that will produce high quality, high performance active matrix reflective and emissive flexible display technology demonstrators (TDs). Electrophoretic ink and cholesteric liquid crystals have been selected as Center reflective imaging layer technologies; these technologies are attractive because they are fully reflective and bistable (extremely low power) and because the materials are environmentally robust and intrinsically rugged. Organic light emitting devices (OLEDs) have been chosen as the emissive imaging layer technology. These three electro-optic subsystems will be integrated with a flexible a-Si thin film transistor active matrix backplane platform. We have created the integrated design, backplane fabrication, display assembly, test and evaluation capability to enable rapid cycles of learning and technology development. Backplane fabrication is currently accomplished on a 6” wafer scale pilot line linked to a Manufacturing Execution System and supported by a comprehensive suite of in-fab metrology tools. We are currently installing a GEN II pilot line, with qualified operation slated for 2006. This line will be used to demonstrate process and display form factor capability, while providing high yield low volume manufacturing of pilot-scale levels of technology demonstrators for the Army and our commercial partners.

Direct Fabrication of a-Si:H Thin Film Transistor Arrays on Flexible Plastic Film and Metal Foil Substrates: Critical Challenges and Enabling Solutions

In this paper we describe solutions to effectively address critical challenges in direct fabrication of amorphous silicon thin film transistor (TFTs) arrays for active matrix flexible displays. For both metal foil and plastic flexible substrates a manufacturable handling protocol in automated display-scale equipment is required. We have successfully demonstrated a temporary bonding protocol that required development of new enabling materials, tools and processes. For metal foil substrates, the principal challenges are planarization and electrical isolation, and management of stress (CTE mismatch) during TFT fabrication. For plastic substrates, the principal challenges are dimensional instability management in conjunction with manufacturing-ready temporary adhesives. Solutions required a systems-level approach to address the challenges of the substrates and their handling simultaneously.

Disposable point-of-use optical biosensor for multiple biomarker detection

This work explored the viability of a new miniaturized fluorescence measurement-based sensor architecture using organic light emitting diode (OLED) display and photodiode active matrix array technology for point-of-use diagnosis of multiple disease biomarkers in a low cost disposable configuration. Sensor feasibility and optical performance were evaluated using a bright 0.3mW/mm2 2 × 2 mm, 455nm blue OLED emitter test structure configured first with orthogonally crossed linear polarizing film; and second, with band-pass and long-pass optical filters. Preliminary measurement results indicated that this type of sensor architecture requires optical filters to approach the sensitivity of laboratory fluorescence-based instrumentation.

Efficiency enhancement in small molecular organic photovoltaic devices employing dual anode interfacial layers

We demonstrated enhanced efficiency in small molecule organic photovoltaic devices using dual organic interfacial layers of PEDOT:PSS followed by tetracene between the ITO anode and the organic donor material. The use of a small molecular templating layer, such as tetracene, proved to increase the molecular stacking of the subsequent phthalocyanine (Pc) based donor materials. Upon application in planar heterojunction devices of ZnPc and C60, an enhancement of over 80 percent in the donor contribution to the external quantum efficiency was observed attributed to the combination of exciton blocking by the higher band gap tetracene layer and enhanced exciton diffusion and charge transport resulting from the increased crystallinity.