Tuning the Optical Properties of CsPbBr3 Nanocrystals by Anion Exchange Reactions with CsX Aqueous Solution

Topotactic anion exchange has been developed to tune the composition and band gap energies of cesium lead halide (CsPbX3) perovskite nanocrystals (NCs). However, current anion exchange methods either require harsh conditions or take a long time to realize substantial substitution. Here, we present a method to modulate the composition of colloidal CsPbBr3 NCs through ultrasonication-assisted anion exchange with CsX (X = Cl, I) solution. Efficient anion exchange of CsPbBr3 NCs with Cl-or I-is realized with substitution ratio up to 93% and preservation of the pristine shape and structure of CsPbBr3 NCs. This anion exchange results in tunable emission, covering the whole visible spectral range, with relatively high photoluminescence quantum yield, narrow emission bandwidths, and good stability. This work provides a facile and efficient way to engineer the properties of halide perovskite NCs and has great potential for large-scale production of compositionally diverse perovskite NCs.