Low Operation Voltage White Organic Light-Emitting Diodes with Excellent Color Stability based on Gradient-Doping Sensitization System

With tremendous progresses in material synthesis and device engineering, white organic light-emitting diodes (OLEDs) have achieved continuous breakthroughs in brightness and efficiencies. Regrettably, as another important index, color stability is still a thorny problem restricting the industrial development of white OLEDs. Herein, a gradient-doping sensitization system is constructed to realize low operation voltage white OLEDs with excellent color stability by gradient doping europium complex into light-emitting layer (EML) as sensitizer. The gradient-doping sensitization system realizes the precise regulation of carriers' distribution and the reasonable assignment of recombination zone in different EMLs, thus leading to low turn-on voltage of 2.3 V and negligible chromaticity coordinates variation of (0.005, 0.002) over wide brightness range of 1000-20 000 cd m(-2). Meanwhile, the obtained white OLED realizes the maximum brightness of 67 384 cd m(-2), current efficiency (eta(c)) of 65.27 cd A(-1), power efficiency (eta(p)) of 73.24 lm W-1, and external quantum efficiency of 29.93%. The gradient-doping sensitization system provides an efficient and reliable strategy for designing white OLEDs with improved color stability and reduced power consumption.