Abstract
Herein we demonstrate a facile approach for the synthesis of all inorganic cesium lead halide perovskite nanocrystal composites CsPbX3 (X = Cl, Br, I) with high quantum yield by post-synthetic modulation of zero dimensional Cs4PbBr6 nanocrystals with ZnX2 salts. The transformation of Cs4PbBr6 nanocrystals into CsPbBr3 takes place in two steps, the first step being the surface modification of the Cs4PbBr6 nanocrystals with Zn2+ ions and the second step being extraction of CsBr by the Zn2+ ions resulting in the formation of composite Cs4PbBr6/CsPbBr3 nanocrystals. The transformed composite nanocrystals were found to have a PL QY exceeding 90% and the shape of the nanocrystals also changed from hexagonal to cubic shaped. Owing to the highly ionic nature of the nanocrystals, complete anion exchange could be also realized using ZnI2 salt. In the case of the iodide post-treated samples, nanorods were obtained which exhibited bright red photoluminescence. Photodetectors based on the ZnI2 treated Cs4PbBr6 NCs were fabricated, and the photodetectors exhibited a high on/off ratio with a fast response time. The excellent optoelectronic properties make this treatment versatile for a wide range of functional optoelectronic devices like light emitting diodes and photovoltaic devices.