Enhancing luminance response during gray-level transitions at low frequencies in AMOLED displays

Abstract This study proposes a novel driving method to address temporal response degradation observed during gray-level transitions under low-frequency operation in low-temperature poly-Si and oxide (LTPO) active-matrix organic light-emitting diode (AMOLED) displays. Through experimental investigation, we demonstrate that the delayed response is primarily attributed to the hysteresis behavior of the driving thin-film transistor (D-TFT), leading to a threshold voltage (VTH) shift and delayed recovery during black-to-white transitions (i.e., gray-level transition). Moreover, the VTH shift can distort the parasitic coupling effect during the programming phase, leading to further degradation in temporal response. To mitigate this issue, we evaluate two approaches, increasing a reset voltage and introducing short-duration high-frequency frame insertion during gray-level transitions to facilitate rapid VTH recovery. Through this, we demonstrate that while both methods improve the luminance response, the frame insertion technique achieves superior performance particularly in luminance stability. This frame insertion method improved the first-second luminance response from 68.1% to 98.2%, while achieving this enhancement with only a 0.6% increase in power consumption through power-efficient optimization. This approach significantly enhances display performance under low-refresh-rate operation, such as in always-on display (AoD) modes.