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

Abstract 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 (η c ) of 65.27 cd A −1 , power efficiency (η 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.