Efficiency Enhancement of Organic Light Emitting Diodes with Black Matrices

Organic Light-Emitting Diode (OLED) can achieve a shorter response time and better color quality than Thin-Film-Transistor Liquid Crystal Display (TFT-LCD), the mostly used display technology recently. Furthermore, OLED displays have the advantage of being made on flexible substrate. Also, the high color rendering index, the adjustable color temperature, and the surface emitting source makes OLED important in both the display and lighting industry in the future. The biggest confrontation of OLED is that its multi-layer structure and large amount of the light emitted from the organic layer will be trapped within the layers by total internal reflection (TIR). Micro-lens array films (MAFs) is used solve the problem. It breaks down the TIR between glass substrate and the air. Black matrix (BM) layer is normally used to reduce the ambient light when using OLED structure, which might cause a significant drop in the contrast ratio. The BM layer, however reduce the light out-coupling efficiency in a very effective way. Through examinations, we studied the light out-coupling improvement mechanism of the MAFs, and found out why the BM layer causes such a huge difference. In this study, we also give out four possible optimizations on the OLED structure to avoid the trade-off between BM and MAFs.