Preparation of surface modified CsPbBr3@CsPb2Br5 nanocrystals with high stability by a pseudo-peritectic method.

Lead halide perovskite CsPbBr 3 nanocrystals (NCs) have attracted great interest in recent years owing to their excellent properties such as strong light absorption, high photoluminescence quantum yield (PLQY), good wavelength tunability, and narrow FWHM. However, their instability is still a bottleneck for their potential application. In this work, a pseudo-peritectic method, which is a peritectic reaction in solutions, was proposed. The phenomenon of "Survival of the fittest" was observed. The synthesized CsPb 2 Br 5 phase greatly reduces the surface defects, and improves the stability and PL properties. The pseudo-peritectic method using for preparing surface modified CsPbBr 3 @CsPb 2 Br 5 nanocrystals is a significant pathway to achieve long-term stable lead halide perovskite for optoelectronic devices. • A pseudo-peritectic method was proposed to prepare surface modified CsPbBr 3 @CsPb 2 Br 5 nanocrystals. • The phenomenon of "Survival of the fittest" was observed. • The CsPb 2 Br 5 phase has no impacts on light emission of CsPbBr 3 , but greatly improves the stability and the PL properties. • The fluorescence quantum efficiency of CsPbBr 3 @CsPb 2 Br 5 composite nanocrystals is up to 70% after 72 h in water. [ABSTRACT FROM AUTHOR]