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

The anion-exchange among halogen ions is an effective technique for tuning the chemical composition and emission color of all-inorganic halide perovskite CsPbX 3 (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(I 1-x Br x ) 3 (0 ≤ x ≤ 1) has been finely tuned through tailoring its bandgap with the anion-exchange between CsPbI 3 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 CsPbI 3 and BBAThe trace of water added into the system can hinder the spontaneous transformation from red CsPbI 3 to CsPbBr 3 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.