Improvement of the Electroluminescence Performance of Exciplex‐Based OLEDs by Effective Utilization of Long‐Range Coupled Electron–Hole Pairs

Abstract

AbstractAn effective method to utilize the radiation of long‐range coupled electron–hole pairs to improve the electroluminescence performance of exciplex‐based organic light‐emitting diodes (OLEDs) is realized by codoping an organic spacer into the bulk‐heterojunction exciplex emitter. The photoluminescence properties of the codoped films reveal that the fraction of delayed fluorescence will be clearly strengthened with an increasing codoping ratio, indicating that more triplet excitons can be utilized effectively, thus greatly enhancing the efficiency of exciplex‐based OLEDs. The maximum external quantum efficiency is improved by ≈105%, from 3.9% to 8.0%, and maintains 7.5% at a luminance of 1000 cd m−2; the codoped devices with the spacer also exhibit excellent spectrum stability under various applied voltages. Magneto‐electroluminescence properties are also investigated to verify the radiative process of long‐range coupled electron–hole pairs. Furthermore, based on this codoped system, low driving voltage, high efficiency, and low efficiency roll‐off are achieved in the orange phosphorescence OLEDs, indicating the advantage of this method in exciton regulation and utilization. This work can assist for further research to achieve high‐performance exciplex‐based OLEDs by adjusting the exciton behavior in device structure design.