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 (VBr) 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.