Microemulsion-Induced Stable CsPbBr3/PbWO4 Nanocrystals for Light-Emitting Diodes

All-inorganic cesium lead halide perovskite colloidal nanocrystals (NCs) (CsPbX 3 , X = Cl, Br, I) have emerged as potential candidates for next-generation light-emitting diodes (LEDs). However, high trap states on the surface of CsPbX 3 NCs caused by ionic nature and dynamic bonding of organic ligands limit the performance of CsPbX 3 NCs-based LEDs. Herein, a microemulsion (ME)-modified strategy to decorate CsPbBr 3 NC cores with inorganic PbWO 4 is developed. It is demonstrated that ME-assisted modification plays a crucial role in bridging the WO 4 2− anion solution and the CsPbBr 3 NC suspension. Compared with pristine CsPbBr 3 NCs, the obtained PbWO 4 -modified NCs exhibit improved photoluminescence efficiency. The corresponding NC films also show enhanced stability at elevated temperature and also in humid atmosphere. Consequently, the PbWO 4 -modified NCs-based LED exhibits a pronounced improvement of electroluminescence with an external quantum efficiency from 0.2% to 5.7% and twofold enhancement of the operational lifetime through PbWO 4 passivation in comparison with that of pristine CsPbBr 3 NCs-based LED. These results show a promising pathway by ME-induced anionic modification for high-performance and stable LEDs based on perovskite NCs.