Highly efficient fluorescent organic electroluminescent diodes based on doping-free phosphorescent sensitization system

Actualizing highly efficient fluorescent organic light-emitting diodes (OLEDs) based on phosphorescent sensitization with simplified structure is still a challenge due to employment of multiple doping technology. In this paper, efficient orange fluorescent OLEDs are successfully realized by combining doping-free phosphorescent sensitization system with thermally activated delayed fluorescence host. By introducing multi-ultrathin phosphor sensitization layers in orange fluorescent emission layer, maximum external quantum efficiencies of 14.1% is achieved in the resulting device. The exciton recombination behavior is demonstrated by systematic investigation of energy transfer mechanism. Moreover, the warm white device is realized by manipulating doping level of orange dye, achieving power efficiency of 38.5 lm/W with high color stability. Our strategy showcases an effective route for the practical applications of high-performance OLEDs based on simplified structures.