Improvement in optical properties of Cs₄PbBr₆ nanocrystals using aprotic polar purification solvent

We demonstrate the influence mechanism on the optical property of Cs₄PbBr₆ during purification of solution with different protonated levels and polarities. During the purification process, organic groups originating from oleic acid (OA) and PbBr impurity on the surface of Cs₄PbBr₆ nanocrystals can be removed using high polarity aprotic and protonic solvents, and the number of Br vacancies (V _Br) can be reduced. The protonic polar solvent can not only etch the organic groups on the surface of nanocrystals, causing surface reconstruction and particle growth of nanocrystals, but also enter into the lattice of Cs₄PbBr₆ and react with the embedded CsPbBr₃. However, aprotic polar solvent decreases the particle size of Cs₄PbBr₆ nanocrystals with the increase in the solvent polarity. The optical properties of Cs₄PbBr₆ can be effectively improved using aprotic polar solvents as a purification solvent, which is very significant to improve the luminescence efficiency of perovskites.