Cesium lead halide perovskites emitting blue light in the 460−470 nm range of wavelengths have so far been plagued with rather poor luminescent performance, placing inevitable limitations on the development of perovskite nanocrystal-based blue light-emitting devices. Herein, a selective surface defect elimination process with the help of hydrated nitrates was introduced into the perovskite/toluene solution to strip the undesired surface defects and vacancies and to boost the photoluminescence quantum yield of true-blue-light-emitting (at 466 nm) CsPb(Cl/Br) 3 perovskite nanocrystals to the impressive value of 85%. Unlike the conventional passivation strategy, the anionic nitrate ions are able to desorb the undesired surface metallic lead and combine with excess surface metal ions, leaving perovskite quantum dots with better crystallinity and fewer surface defects.

Figure 4. a) FTIR spectra and b) Raman spectra (taken under excitation at 633 nm) of the pristine (black), the "2 s OxA" (red), and the "10 min OxA" (blue) CsPb(Cl/Br) 3 perovskite NCs.

We report a facile and low‐cost synthesis of WS2 quantum dots with bright broad‐band emission, which are suitable for lighting applications. The thus fabricated WS2 light‐emitting diodes (LEDs) exhibit voltage independent electroluminescence spectra, and the optimized white LEDs generate a high color rendering index of 93.