Direct synthesis of ethanolamine-capped alcohol-soluble Zn-doped SnO2 nanocrystals and their application in quantum dot light-emitting diodes

Abstract

An electron transport layer (ETL) plays a crucial role in determining the performance of quantum dot light-emitting diodes (QLEDs), and ZnO nanoparticles (NPs) are widely recognized as the most promising ETL material for group II–VI and III–V QLEDs. However, ZnO NPs are sensitive to water vapor in the air, leading to instability under ambient conditions. SnO₂ NPs have emerged as a promising alternative to ZnO NPs owing to their superior properties. Currently, the synthesis of SnO₂ NPs typically involves high-temperature reactions, which significantly increase energy consumption and production costs. In addition, alcohol-soluble SnO₂ NPs demonstrate superior performance in terms of their environmentally benign nature, film-forming qualities, and device efficiency. Nevertheless, existing methods for preparing alcohol-soluble SnO₂ NPs often require a post-ligand exchange process using dimethyl sulfoxide (DMSO) or ethanolamine. Zn doping of SnO₂ NPs has been shown to effectively reduce the concentration of hydroxyl (–OH) groups on the surface of SnO₂ NPs, thereby alleviating fluorescence quenching and enhancing the performance of the resultant QLEDs. In this study, we develop a direct synthetic method for producing alcohol-soluble Zn-doped SnO₂ NPs using short-chain ethanolamine as a stabilizing agent. The optimal performance of a QLED, with a maximum external quantum efficiency (EQE) of 12.77% and a current efficiency of 19.03 cd A⁻¹, is achieved based on Zn-doped SnO₂ NPs with a Zn doping concentration of 10%, an average particle size of 2.13 nm, and an optical band gap of 4.58 eV, demonstrating the significant potential of the doped SnO₂ NPs as an ETL material in QLEDs.