Overcoming the Photoinduced Solvent-Assisted Anion Exchange Reactions of CsPbBr₃ Perovskite Nanocrystals

Abstract

Photocatalytic solvent-assisted anion exchange of lead halide perovskites are extremely important, as it can tune the redox properties/band positions of the perovskite nanocrystals. Among that, the generation of chloride ions from the solvents chloroform and dichloromethane by accepting an electron from the photoexcited CsPbBr 3 nanocrystals and the resulting anion exchanges are investigated. The redox potentials of the solvent molecules and the band positions of the semiconductor allow for the photoinduced electron transfer process, thermodynamically, in these two solvents. However, the presence of a better electron acceptor N-bromosuccinimide (NBS) can prevent the photocatalytic solvent-assisted chloride ion exchange reactions in CsPbBr 3 . The preferential interaction of Pb 2+ of lead halide perovskites with the bromide ions in preference to Cl − , as a result of Pearson's hard soft acid base theory, stabilizes CsPbBr 3 nanocrystals. This is confirmed by using bromine-containing chloroform as the solvent. Interestingly, in the presence of NBS/ bromine, the anion exchange with chloride ions formed by the reduction of solvents can be prevented. The present investigations can give insights into the mechanistic aspects of the anion exchange reaction and suggest new methodologies to stabilize CsPbBr 3 nanocrystals in chlorine-containing solvents.

Probing the Structural Degradation of CsPbBr3 Perovskite Nanocrystals in the Presence of H2O and H2S: How Weak Interactions and HSAB Matter

“…The details of the preparation and purification of all inorganic CsPbBr 3 perovskite nanocrystals are provided in Experimental Section. Oleylamine (OAm) and oleic acid (OA) are the capping agents used for the preparation of nanocrystals, which facilitated the dispersion of CsPbBr 3 nanocrystals in nonpolar organic solvents. , Furthermore, the purified CsPbBr 3 perovskite nanocrystals are characterized using spectroscopic methods, X-ray diffraction, and electron microscopy. The quantum confined nature of the CsPbBr 3 nanocrystals is confirmed by the presence of the excitonic peak in the UV–vis electronic absorption spectrum (Figure A).…”