Improved efficiency of blue phosphorescence organic light-emitting diodes with irregular stepwise-doping emitting layers

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 19.2cdA1 and 18.0lmW1 are achieved, while those of a continuous stepwise-doping device are 9.8cdA1 and 8.6lmW1. The dramatic efficiency enhancement is mainly attributed to the high holeelectron recombination probability and suppressed triplet excitons quenching by fine tuning the doping concentrations in the EMLs.