Enhancing hole injection by electric dipoles for efficient blue InP QLEDs

Yangzhi Tan,Fangqing Zhao,Guanding Mei,Wallace C H Choy,Kai Wang,Jiayun Sun,Zhaojin Wang,Xiangtian Xiao,Wenda Zhang,Xiao Wei Sun,Jingrui Ma,Tianqi Zhang,Dan Wu

doi:10.1063/5.0071508

Abstract

The unbalanced carrier injection is a key factor that deteriorates the performance of blue InP quantum dot light-emitting diodes (QLEDs). Therefore, to achieve efficient blue InP QLEDs, an effective strategy that balances carrier injection through enhancing the hole injection and transport is in demand. In this study, we introduced an ultrathin MoO3 electric dipole layer between the hole injection layer and the hole transport layer (HTL) to form a pair of dipole-induced built-in electric fields with forward resultant direction to enhance hole injection and facilitate the balance of carrier injection. Meanwhile, the p-doping effect by MoO3 leads to increased carrier concentration and decreased trap density of interfacial HTL, therefore improved its effective hole mobility. Consequently, the maximal external quantum efficiency of blue InP QLEDs was enhanced from 1.0% to 2.1%. This work provides an effective method to balance carrier injection by modulating hole injection and transport, indicating the feasibility to realize high-efficiency QLEDs.

Highlights

The highest reported external quantum efficiency (EQE) of blue InP quantum dot light-emitting diodes (QLEDs) is only 2.5% (Ref. 9) so far, which is far from the figure of Cd-based blue QLEDs.3 The relatively low efficiency of blue InP QLEDs could be attributed to several reasons
The unbalanced carrier injection is a key factor that deteriorates the performance of blue InP quantum dot light-emitting diodes (QLEDs)
We introduced an ultrathin MoO3 electric dipole layer between the hole injection layer and the hole transport layer (HTL) to form a pair of dipole-induced built-in electric fields with forward resultant direction to enhance hole injection and facilitate the balance of carrier injection

Summary

Introduction

The highest reported EQE of blue InP QLEDs is only 2.5% (Ref. 9) so far, which is far from the figure of Cd-based blue QLEDs.3 The relatively low efficiency of blue InP QLEDs could be attributed to several reasons. To achieve efficient blue InP QLEDs, an effective strategy that balances carrier injection through enhancing the hole injection and transport is in demand.

Results

Conclusion