Energy-Band Alignment and Charge Balance of Electron Transport Layer With Quinary Zn–Mg–Ga–Cl–O Nanoparticles in InP-Based Quantum Dot Light Emitting Diodes

Abstract

Quinary Zn-Mg-Ga-Cl-O nanoparticles were synthesized for the electron transport layer (ETL) of green InP-based quantum dot light emitting diodes (QLEDs) to achieve band alignment and charge balance. These nanoparticles were synthesized by simple hydrolysis reactions in the solution phase. The band gap of Zn-Mg-Ga-Cl-O increased to 3.85 eV, which exceeded that of ZnO by 0.3 eV. The energy gap between the conduction bands of Zn-Mg-Ga-Cl-O and InP-based quantum dots changed from 0.78 eV to −0.17 eV. Electron transport in green InP-based QLEDs was reduced, and the charge balance was improved by Zn-Mg-Ga-Cl-O compared with that by ZnO and Zn-Mg-O. Green InP-based QLEDs with a Zn-Mg-Ga-Cl-O ETL exhibited a maximum luminance of 3270 cd/m2. The maximum external quantum efficiency (EQE) and power efficiency of the QLEDs with a Zn-Mg-Ga-Cl-O ETL were 3.8% and 19.6 lm/W, respectively, which were 9.5 times and 9.24 times higher than those of the QLEDs with a ZnO ETL. The maximum EQE and power efficiency were achieved at 2.5 V and 170 cd/m2.