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Keywords:

  • doping profile;
  • efficiency;
  • organic light-emitting diodes;
  • phosphorescence

Abstract

We demonstrate highly efficient blue phosphorescence organic light-emitting diodes (PHOLED) with irregular stepwise-doping emitting layers (EMLs). High efficiency is realized by inserting a high-doping EML between two relatively low-doping EMLs. Peak luminous efficiency and power efficiency of 19.2 cd A−1 and 18.0 lm W−1 are achieved, while those of a continuous stepwise-doping device are 9.8 cd A−1 and 8.6 lm W−1. The dramatic efficiency enhancement is mainly attributed to the high hole–electron recombination probability and suppressed triplet excitons quenching by fine tuning the doping concentrations in the EMLs.