Comprehensive analysis and optimal design of top-emitting organic light-emitting devices

We present an accurate analysis of light emission in top-emitting organic light-emitting devices (TOLEDs) by explicitly considering the Purcell effect. TOLEDs are optimized separately for maximum zero-degree luminance, maximum electroluminescence (EL) efficiency, and wide viewing angle with high EL efficiency. For fluorescent material with an internal quantum efficiency $(ηint0)$ of 0.25, the maximum zero-degree luminance and EL efficiency can be achieved by locating the emitters around the first antinode of the microcavity while for phosphorescent material with $ηint0=1.0$⁠, the maximum zero-degree luminance and EL efficiency are around the second antinode. Through relaxing the efficiency by 10%–20%, the angular intensity distribution can be even better than the Lambertian distribution; meanwhile, the color shows only a small variation over an angle range of 150°. Our results, which are in good agreement with experiments, show that the Purcell effect on TOLED performances is significant and should be carefully examined in studying TOLEDs.