Quantitative analysis of pixel crosstalk in AMOLED displays

The resolution of organic light-emitting diode (OLED) displays is increasing steadily as these displays are adopted for mobile and virtual reality (VR) devices. This leads to a stronger pixel crosstalk effect, where the neighbors of active pixels unintentionally emit light due to a lateral electric current between the pixels. Recently, the crosstalk was quantified by measuring the current flowing through the common hole transport layer between the neighboring pixels and comparing it to the current through the active pixel diode [S.-K. Kwon, K.-S. Kim, H.-C. Choi and J. H. Kwon, presented at the International Meeting on Information Display, Jeju, South Korea, 2016]. The measurements showed that the crosstalk is more crucial for low light levels. In such cases, the intended and parasitic currents are similar. The simulations performed in this study validated these measurement results. By simulations, we quantify the crosstalk current through the diode. The luminous intensity can be calculated with the measured current efficiency of the diodes. For low light levels, the unintended luminance can reach up to 40% of the intended luminance. The luminance due to pixel crosstalk is perceivable by humans. This effect should be considered for OLED displays with resolutions higher than 300 PPI.

有机发光二极管（organic light-emitting diode，OLED）显示屏的分辨率正稳步提升，随着这类显示技术被广泛应用于移动设备与虚拟现实（virtual reality，VR）终端，由此引发的像素串扰效应也愈发显著：有源像素的邻接像素会因像素间的横向电流而产生非预期的发光行为。近期有研究通过测量相邻像素间共用空穴传输层的电流，并将其与有源像素二极管的电流进行对比，实现了对串扰效应的量化分析[S.-K. Kwon、K.-S. Kim、H.-C. Choi 与 J. H. Kwon，2016年于韩国济州岛举办的国际信息显示会议（International Meeting on Information Display）]。测量结果表明，串扰效应在低亮度环境下影响更为突出，此时系统的预期电流与寄生电流水平相近；本研究开展的仿真实验验证了前述测量结果，并通过仿真对二极管的串扰电流实现了量化表征，可借助二极管的实测电流效率计算其发光强度。针对低亮度场景，非预期发光亮度最高可达预期发光亮度的40%，像素串扰引发的非预期亮度具备可感知性，即人眼可察觉此类串扰发光现象。对于分辨率高于300像素每英寸（Pixels Per Inch，PPI）的OLED显示屏，该效应需被纳入设计与优化的考量范畴。