Effect of Air Exposure of ZnMgO Nanoparticle Electron Transport Layer on Efficiency of Quantum-Dot Light-Emitting Diodes

We demonstrate the effect of air exposure on optical and electrical properties of ZnMgO nanoparticles (NPs) typically exploited as an electron transport layer in Cd-based quantum-dot light-emitting diodes (QLEDs). We analyze the roles of air components in modifying the electrical properties of ZnMgO NPs, which reveals that H2O enables the reduction of hole leakage while O-2 alters the character of charge transport due to its ability to trap electrons. As a result, the charge balance in the QDs layer is improved, which is confirmed by voltage-dependent measurements of photoluminescence quantum yield. The maximum external quantum efficiency is improved over 2-fold and reaches the value of 9.5% at a luminance of 10(4) cd/m(2). In addition, we investigate the problem of electron leakage into the hole transport layer and show that trap-mediated electron transport in the ZnMgO layer caused by adsorbed O-2 ensures a higher leakage threshold. This work also provides an insight into the possible disadvantages of device contact with air as well as problems and challenges that might occur during open-air fabrication of QLEDs.

Automated summary

This study demonstrates the impact of air exposure on the optical and electrical properties of ZnMgO nanoparticles, revealing that different air components play roles in modifying the electrical properties. The findings show that H2O reduces hole leakage while O-2 traps electrons, improving charge balance in the quantum-dot layer and increasing external quantum efficiency by over 2-fold. This work also highlights the potential disadvantages of device contact with air and challenges in open-air fabrication of QLEDs.