Highly luminescent and stable CsPbBr₃ perovskite nanocrystals coated with polyethersulfone for white light‐emitting diode applications

Simultaneously improving the stability and photoluminescence quantum yield (PLQY) of all inorganic perovskite nanocrystals (NCs) is crucial for their practical utilization in various optoelectronic devices. Here, CsPbBr 3 NCs coated with polyethersulfone (PES) were prepared via an in‐situ co‐precipitation method. The sulfone groups in PES bind to undercoordinated lead ion (Pb 2+ ) on the CsPbBr 3 NCs, resulting in significant reduction of surface defects, thus enhancing the PLQY from 74.2% to 88.3%. Meanwhile, the PES‐coated NCs exhibit high water resistance and excellent heat and light stability, maintaining over 85% of the initial PL intensity under thermal aging (70°C, 4 h) and continuous 365 nm ultraviolet (UV) light irradiation (24 W, 8 h) conditions. By contrast, the PL intensity of the control NCs dramatically dropped to less than 40%. Finally, a diode emitting bright white light was fabricated utilizing the PES‐coated CsPbBr 3 NCs, which exhibits a color gamut of ~110% NTSC standard.