Invited paper: Amorphous silicon tft’s with 100-year lifetimes in a clear plastic compatible process for amoleds

We demonstrate critical elements of a-Si technology on clear plastic for flexible AMOLED applications. First, we show that a-Si TFT’s with gate voltages under 5 V provide sufficient current for OLED pixel brightness of over 1000 cd/m², with minimum geometries (W/L = 1) for 100 µm × 100 µm pixels. Critical to this result is a clear plastic with the combined properties of high transparency, glass transition temperature in excess of 300^oC, and low coefficient of thermal expansion. Second, we show that by engineering the a-Si TFT stack, under the bias conditions for pixel operation, the “half-life” of the TFT (defined as the time for the current to fall by 50% in DC operation) is 10 years for a 280^oC process on clear plastic, and at least 100 years for 300^oC. This is several orders of magnitude higher than that of common a-Si TFT processes and in general larger than the lifetimes for the 50% decay of the luminescence of the OLED’s themselves. Finally, we provide a framework demonstrating the tradeoff between drive current and TFT stability.