Improving Flicker of Low-Refresh-Rate Driven Active-Matrix Organic Light-Emitting Diode Display

Abstract

The brightness of low-temperature polycrystalline silicon and metal-oxide (LTPO) active-matrix organic light-emitting diode (AMOLED) display under low-refresh-rate driving condition tends to increase during pixel voltage holding time of each frame even though there is no critical leakage current path from the storage capacitor. We have found that the main cause of the brightness increase is electron trapping into the gate insulator of driving thin-film transistor (DTFT) which operates in the saturation mode prone to hot carrier injection. We propose a novel driving method to suppress the brightness variation by applying a high voltage to the source and drain of the DTFT during the non-emitting time which is inserted periodically for dimming the organic light-emitting diode (OLED) display. Our experimental results show that the brightness variation can be reduced from 3.7 % to 1.4 % at the 63rd gray level by the proposed DTFT reset scheme.