Surface Defect\nRecovery in Perovskite Nanocrystals\nwith Excess Halide for Core–Shell Structure

We present a method to synthesize stable and uniform\nhigh-quality\nperovskite nanocrystals (PNCs) by using excess halide to recover\nsurface defects in CsPbBr<sub>3</sub>/ZnS core/shell nanocrystals.\nUse of <i>N</i>-bromosuccinimide as a halide donor recovered\nsurface halide vacancies of bare CsPbBr<sub>3</sub> PNCs during the\ngrowth of the ZnS shell, as confirmed by DFT calculations. This approach\nachieves a high photoluminescence quantum yield of nearly 1, and significantly\nincreases the stability of PNCs under adverse conditions such as high\nhumidity and elevated temperature. CsPbBr<sub>3</sub>/ZnS PNC light-emitting\ndiodes demonstrated outstanding luminous characteristics, with a remarkable\nexternal quantum efficiency of 12.77% and a maximum luminance of 1449\ncd m<sup>–2</sup> at 517 nm. These characteristics of the PNCs\nwill have a wide variety of applications and will help enable development\nof highly efficient optoelectronic devices.