The practical application of all-inorganic semiconductor lead halide perovskite nanocrystals (LHP NCs) has been limited by their poor stability. Recently, a lot of research on core–shell structure has been done to improve the stability of perovskite NCs, but the effect was far from the application requirements. Herein, we, for the first time, report a convenient approach to synthesize organic–inorganic double shell CsPbBr₃@SiO₂@polystyrene (PS) NCs with an inter-core of CsPbBr₃, the intermediate layer of SiO₂ shell, and outmost PS shell. Particularly, the CsPbBr₃@SiO₂@PS NCs maintained more than 90% of their initial photoluminescence (PL) intensity under one month's ultraviolet lamp irradiation or in 85 °C and 85% relative humidity (RH) condition. The white-light-emitting-diodes (WLEDs) were fabricated by encapsulating commercial InGaN chip with CsPbBr₃@SiO₂@PS NCs and K₂SiF₆:Mn⁴⁺ (KSF:Mn⁴⁺) phosphor with a luminous efficacy of ~ 100 lm/W at 20 mA current and a color gamut of 128% of the National Television Standards Committee (NTSC) standard. In addition, these WLEDs still maintain 91% of the initial luminous efficacy after 1200 h of continuous lighting. These results demonstrated that double shell-protected CsPbBr₃ perovskite NCs have great potential in the field of WLEDs.

All-inorganic cesium lead halide perovskite nanocrystals (CsPbX₃, X = Cl, Br, I) have attracted considerable scientific and technological interest due to their precise bandgap tunability, high color purity and efficient luminescence. Nevertheless, their poor stability in harsh conditions such as moisture, ultraviolet (UV) light irradiation and high temperature, is a major obstacle for their further commercial applications. Herein, by simply using a new type of precursor, namely "HPbX₃" (X = Cl, Br, I), we can achieve the coordination equilibrium for Pb precursors during reaction and obtain high-quality perovskite nanocrystals with tremendously enhanced luminous efficiency and chemical stability based on hot-injection method. The prepared α-CsPbI₃ nanocrystals exhibit an extremely high photoluminescence quantum yield of 96% and keep stable in air for more than two months without any post-synthesis treatment. Moreover, stability evaluations under UV light irradiation, water or thermal impact are also performed and the results show substantially improved stability of these nanocrystals as compared with the samples prepared using traditional PbI₂ as precursor. Through temperature-dependent (10–300 K) steady and transient spectral analysis combined with compositional measurements, it is revealed that the lower structural defect density, which is guaranteed by abundant halogen when using HPbX₃ as precursor, is the most important reason for such performance enhancement.