A theoretical analysis of the performance of organic light emission diode based flat panel display is presented for three different color reproduction approaches, i.e. color produced by three primary color emitters, color produced by blue emitters coupled with phosphor filters, and color produced by white emitters coupled with transmission color filters. The validity of this simulation is examined with test results from real AMOLED panels made with three primary color emitters.
Kalluri Sarma, Charles Chanley, Sonia Dodd, Jared Roush, John Schmidt, Gordana Srdanov, Matthew Stevenson, Ralf Wessel, Jeffrey Innocenzo, Gang Yu, Marie O'Regan, W. MacDonald, R. Eveson, Ke Long, Helena Gleskova, Sigurd Wagner, James Sturm
Flexible displays fabricated using plastic substrates have a potential for being very thin, light weight, highly rugged with greatly minimized propensity for breakage, roll-to-roll manufacturing and lower cost. The emerging OLED display media offers the advantage of being a solid state and rugged structure for flexible displays in addition to the many potential advantages of an AM OLED over the currently dominant AM LCD. The current high level of interest in flexible displays is facilitating the development of the required enabling technologies which include development of plastic substrates, low temperature active matrix device and backplane fabrication, and display packaging. In the following we will first discuss our development efforts in the PEN based plastic substrates, active matrix backplane technology, low temperature (150°C) a-Si TFT devices and an AM OLED test chip used for evaluating various candidate designs. We will then describe the design, fabrication and successful evaluation and demonstration of a 64x64 pixel AM OLED test display using a-Si TFT backplane fabricated at 150°C on the flexible plastic substrate.
Gang Yu, Gordana Srdanov, Belinda Zhang, Matthew Stevenson, Jian Wang, Peter Chen, Erlinda Baggao, Johnny Macias, Runguang Sun, Charlie McPherson, Paul Sant, Jeffrey Innocenzo, Matthew Stainer, Marie O'Regan
Active-matrix organic/polyeric light emitting displays (AMOLEDs/AMPLEDs) are of great potentials for high information content display applications. They offer high brightness, fast response time, high image quality (high contrast, high gray levels and small pixel pitch size) and low power consumption. AMPLEDs are ideal for portable electronic devices such as web-phones, personal data assistants, GPS and handhold computers. AMPLEDs are especially suitable for motion picture applications. Since the image pixels consume power only when they are turned on, and only consume the power necessary for their corresponding brightness, video displays made with AMOLED/AMPLED reduce power consumption and extend display lifetime considerably. Motion picture applications also minimize image retention and optimize display homogeneity. In this presentation, we discuss our recent progress on AMPLEDs and compare their performance with that of AMLCD.
Polymer photovoltaic cells and photodetectors have passed their infancy and become mature technologies. The energy conversion efficiency of polymer photovoltaic cells have been improved to over 4.1% (500 nm, 10 mW/cm2). Such high efficiency polymer photovoltaic cells are promising for many applications including e-papers, e-books and smart- windows. The development of polymer photodetectors is even faster. The performance parameters have been improved to the level meeting all specifications for practical applications. The polymer photodetectors are of high photosensitivity (approximately 0.2 - 0.3 A/Watt in visible and UV), low dark current (0.1 - 1 nA/cm2), large dynamic range (> 8 orders of magnitude), linear intensity dependence, low noise level and fast response time (to nanosecond time domain). These devices show long shelf and operation lives. The advantages of low manufacturing cost, large detection area, and easy hybridization and integration with other electronic or optical components make the polymer photodetectors promising for a variety of applications including chemical/biomedical analysis, full-color digital image sensing and high energy radiation detection.
In this presentation, we discuss recent progress on polymer photovoltaic cells and polymer photodetectors. By improving the fill-factor of polymer photovoltaic cells, the energy conversion efficiency was improved significantly to over 4 percent. Such high efficiency polymer photovoltaic cells are promising for many applications including e-papers, e-books and smart-windows. Polymer photodetectors with similar device configuration show high photosensitivity, low dark current, large dynamic range, linear intensity dependence, low noise level and fast response time. These parameters are comparable to or even better than their inorganic counterparts. The advantages of low manufacturing cost, large detection area, and easy hybridization and integration with other electronic or optical components make them promising for a variety of applications including chemical/biomedical analysis, full-color digital image sensing and high energy radiation detection.
High sensitivity visible-blind UV detectors were fabricated with organic semiconductors. The photo-sensitivity at 350 nm reaches 75 mA/Watt, corresponding to quantum efficiency of approximately 27% el/ph. The visible/UV suppression ratio is more than 104 without optical filters. These UV detectors are of linear intensity dependence with fast response time. The simple fabrication process allows these UV detectors to be made in large size, in flexible forms or onto non-planar substrates with low cost. The fabrication process also allows these UV detectors to be integrated with electronic devices or optical devices.
Blending organic semiconductors with different electron affinities results in an interpenetrating bi-continuous network of internal donor/acceptor (D/A) heterojunctions. These nano-scale D/A junctions show efficient charge separation and charge transfer. The interpenetrating bi- continuous networks of the donor and the acceptor phases also allow the separated carriers to be collected effectively at the anode and cathode contacts. Typical materials used for the donor phase are conjugated polymers (MEH-PPV). Typical materials used for the acceptor phase are conjugated polymer CN-PPV or fullerene molecules. These photosensitive materials are soluble to common organic solvents, and are processable at room temperature. Photodiodes and photovoltaic cells are fabricated with high quantum efficiencies. The carrier collection efficiency and energy conversion efficiency of MEH-PPV:C60 photovoltaic cells are approximately 29 percent electrons/photon and approximately 3 percent under illumination of 20 mW/cm2 at 430 nm, two orders of magnitude higher than that in devices with MEH-PPV alone. The photosensitivity and the quantum yields increase to 0.26 A/W and approximately 75 percent electrons/photon at reverse bias of -2V, even higher than those in UV-enhanced Si photodiodes at the same wavelength. Large size photodetectors and image sensors have been fabricated with these materials.
Optical quality organic blend films were developed with high photosensitivity. These materials are composed with conjugated polymers, P3OT, or poly(2-methoxy-5-(2-ethyl- hexyloxy)-1,4-phenylene vinylene), MEH-PPV) and fullerene molecules. These blends are soluble to common organic solvents, and are processable at room temperature. Thin film devices in sandwich configurations were fabricated with high quantum efficiency. The carrier collection efficiency and energy conversion efficiency in the MEH-PPV:C60 photovoltaic cells are approximately 29 percent electrons/photons and 2.9 percent respectively, better by more than two orders of magnitude than devices made with MEH-PPV alone. The photosensitivity are even higher with reverse bias, approximately 0.2A/W-0.3A/W in visible region at a few volts. These numbers are comparable to photodiodes made with inorganic semiconductors.
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