Journal Article

LTPO-based pixel circuit with highly uniform luminance and low flicker for variable refresh rate in AMOLED displays

Park, Sang Yoon, Lee, I. Sak, Park, Ji Yeong, Kim, Hyun Jae, Kim, Jae Sung, Yoo, Juhn Suk

2025

Overview

Low-temperature polycrystalline silicon and oxide (LTPO)-based pixel circuits are increasingly being adopted in medium-sized active-matrix organic light-emitting diode (AMOLED) displays due to their power-saving advantages. However, conventional pixel circuits originally developed for mobile displays face challenges when applied to larger panels, due to aggravated IR-drop and residual luminance at black levels. To address these issues, we propose a novel pixel circuit composed of nine thin-film transistors (TFTs) and one storage capacitor (C ST ). The proposed design compensates for luminance non-uniformity caused by IR-drop in the V DD line and ensures stable variable refresh rate (VRR) operation without requiring an additional compensation scheme, such as the on-bias voltage (OBV) used in conventional designs, which causes residual luminance in dark states. To validate the effectiveness of the proposed circuit, a 13-inch LTPO AMOLED panel was fabricated. Flicker was measured to be below − 50 dB at a 10 Hz refresh rate under both 140 nits and 6 nits conditions. In addition, luminance uniformity was significantly improved from 69% to 89% under the high luminance condition of 1,600 nits. These results demonstrate that the proposed pixel circuit achieves improved luminance uniformity and stable VRR performance.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 639/166 / 639/301 / 639/624 / Active-matrix organic light-emitting diode (AMOLED) / Design / Humanities and Social Sciences / IR-drop / Low temperature / Low-temperature polycrystalline silicon and oxide (LTPO) / multidisciplinary / Pixel circuit / Science / Science (multidisciplinary) / Thin films / Variable refresh rate (VRR)