In this paper we develop a new theory to describe the characteristics of amorphous silicon based alloy field-effect transistors. We show that the transition from below to above threshold operation occurs when the Fermi level in the accumulation region moves from the deep to tail localized states in the energy gap. The current-voltage and capacitance-voltage characteristics are related to the basic material parameters such as the distribution of localized states in the energy gap, band mobility, device geometry, channel doping, and series resistances. Our analysis shows that an on current in excess of 2×10−7 A/μm gate width can be obtained with a 10-μm gate length. We also demonstrate that even in the above threshold regime the field-effect mobility is dependent on the gate voltage. Our theory can be used to optimize the design of amorphous silicon based alloy field-effect transistors.

Electrophosphorescent devices with fac-tris(2-phenylpyridine)iridium as the green emitting dopant have been fabricated with a variety of hole and exciton blocking materials. A device with aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolate (BAlq) demonstrates an efficiency of 19 cd/A with a projected operational lifetime of 10 000 h, operated at an initial brightness of 500 cd/m2; or 50 000 h normalized to 100 cd/m2. An orange-red electrophosphorescent device with iridium(III) bis(2-phenylquinolyl-N,C2′)acetylacetonate as the dopant emitter and BAlq as the hole blocker demonstrates a maximum efficiency of 17.6 cd/A with a projected operational lifetime of 5000 h at an initial brightness of 300 cd/m2; or 15 000 h normalized to 100 cd/m2. The average voltage increase for both devices is <0.3 mV/h. The device operational lifetime is found to be inversely proportional to the initial brightness, typical of fluorescent organic light emitting devices.

We describe encapsulated passive matrix, video rate organic light-emitting diode (OLED) displays on flexible plastic substrates using a multilayer barrier encapsulation technology. The flexible OLED (FOLED™) displays are based on highly efficient electrophosphorescent OLED (PHOLED™) technology deposited on barrier coated plastic (Flexible Glass™ substrate) and are hermetically sealed with an optically transmissive multilayer barrier coating (Barix™ encapsulation). Preliminary lifetime to half initial luminance (L0∼100 cd/m2) of order 200 h is achieved on the passive matrix driven encapsulated 80 dpi displays; 2500 h lifetime is achieved on a dc tested encapsulated 5 mm2 FOLED test pixel. The encapsulated displays are flexed 1000 times around a 1 in. diameter cylinder and show minimal damage.

Based on theoretical arguments that top-emitting organic light-emitting devices (TOLEDs) can be more efficient than equivalent bottom-emitting devices, we fabricated TOLEDs comprising reflective anodes and transparent compound cathodes that emit 20.8% more photons in the forward 120° cone than equivalent bottom-emitting OLEDs. Device optimization by tuning the thickness of the top indium–tin–oxide layer according to a microcavity model is also reported.

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A low temperature process for laser dehydrogenation and crystallization of hydrogenated amorphous silicon (a-Si:H) has been developed. This process removes hydrogen by laser irradiations at three energy steps. Studies of hydrogen out-diffusion and microstructure show that hydrogen out-diffusion depends strongly on film structure and the laser energy density. Both high quality and low leakage bottom gate polycrystalline silicon and a-Si:H thin film transistors were monolithically fabricated on the same Corning 7059 glass substrate with a maximum process temperature of only 350 °C.

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We present a new theory describing current-voltage characteristics of amorphous silicon thin-film transistors. We calculate the output conductance in saturation by considering channel shortening effects caused by the space-charge-limited current in the pinch-off region. In this model the drain current is expressed through the free-carrier concentration at the source side of the channel. This allows us to obtain an accurate description of the different operating regimes of a thin-film transistor using one equation that accounts for the dependence of the free-carrier concentration in the channel for different regimes. Our model is in good agreement both with experimental data and the results of our two-dimensional computer simulation. This approach allows one to account for different distributions of localized states in the energy gap. The model has also been developed to be incorporated into a circuit simulator and used for computer-aided design of amorphous silicon integrated circuits.