Realizing high-performance color-tunable WOLED by adjusting the recombination zone and energy distribution in the emitting layer

Color-tunable white organic light-emitting diodes (CT-WOLEDs) having daylight chromaticity and a wide correlated color temperature (CCT) span can mimic our circadian cycle and realize application for lighting or decoration. The effects of the recombination zone and energy distribution on the electro-optical properties and color span are investigated in this paper. We find that it is beneficial to expand the CCT span by increasing the distance between the red ultrathin phosphorescent emissive layer and the center of the recombination zone. By increasing the concentration (y) of mCP in mixed host material in the emitting layer and the thickness (z nm) of the red ultrathin phosphorescent emissive layer, the CCT spans can be expanded towards high CCT and low CCT, respectively. The widest CCT span reaches 4032 K (2391–6423 K) in a simple all-phosphorescent CT-WOLED with a maximum luminance and power efficiency of 9249 cd m⁻² and 15.35 lm W⁻¹, respectively. (paper)