Mercaptopropionic Acid Capped ZnMgO for Efficient and Stable Quantum Dot Light‐Emitting Diodes

Abstract ZnO nanoparticles (NPs) and their derivatives are the most commonly used electron transport materials for quantum dot light‐emitting diodes (QLEDs). However, their ubiquitous issues of severe exciton quenching and poor shelf stability render a limited application in practical use. Herein, the mercaptopropionic acid (MPA)‐capped ZnMgO (MPA‐ZMO) NPs with good optoelectronic properties are proposed to address these problems for efficient and stable QLEDs. The massive oxygen vacancy defects at the ZMO NP surface are effectively passivated by MPA, which inhibits the defect‐associated exciton quenching for bright emission. Besides, an improvement in electron mobility and an upward energy band is also achieved for MPA‐capped ZMO NPs, enabling good carrier injection and transportation. The superior optoelectronic properties contribute great enhancements of the device performances with over 30% increase in external quantum efficiency (EQE) from 16.5 to 21.6% and over 2.5‐fold improvement in a lifetime from 2636.41 to 6601.29 h at 1000 cd m −2 , together with the impressive QLED shelf stability of less than 5% variation in device efficiency during 3‐week storage, showing one of the best performances among currently reported ZMO‐based QLEDs. Consequently, this work contributes an effective approach to decorating the inorganic metal oxide NPs for efficient and stable QLEDs.