A study on the reversible anion-exchange rate in perovskite CsPbX3 nanocrystals

Abstract

The anion-exchange among halogen ions is an effective technique for tuning the chemical composition and emission color of all-inorganic halide perovskite CsPbX3 (X = Cl, Br, and I) nanocrystals by tailoring their bandgaps. This work is focused on the rate of the reversible anion-exchange through finely tuning the luminescence color of perovskite nanocrystals (NCs) in any region between red and green. The luminescence color of the perovskite CsPb(I1-xBrx)3 (0 ≤ x ≤ 1) has been finely tuned through tailoring its bandgap with the anion-exchange between CsPbI3 and 4-bromo-butyric acid (BBA) instead of introducing of bromide salts as starting materials. The BBA could serve as triple functions to afford Br− ions source, short chain ligand with carboxyl group for surface passivation, and weak acid. A systematic study has been carried out to elucidate the effect of experimental parameters, on the color rangeability of the NCs and the anion-exchange rate between CsPbI3 and BBAThe trace of water added into the system can hinder the spontaneous transformation from red CsPbI3 to CsPbBr3 with aging time. It is particularly valuable to realize the reversible processes from green to yellow and finally to red successively by increasing the concentration of the isolated I− ions from various inorganic iodides.