The role of EuBr2 in modulating the crystallization and luminescence of caesium lead bromide

Caesium lead bromide perovskite nanocrystals (PNCs) are synthesized using a room-temperature sonochemical method. By mixing equimolar of CsBr and PbBr 2 in Dimethylformamide (DMF), PNCs of CsPbBr 3 structure are formed. Under an identical reaction condition, when EuBr 2 is introduced with the CsBr/PbBr 2 precursor, the resulted product (Eu-PNCs) becomes zero-dimensional Cs 4 PbBr 6 nanocrystals. In addition to the typical green emission observed in both CsPbBr 3 and Cs 4 PbBr 6 , Eu-PNCs has a blue emission band. The overall photoluminescence quantum yield is much higher than the pristine PNCs. We perform detailed analysis of the crystal structure and luminescence properties of the nanocrystals with and without EuBr 2 modification. An X-ray absorption fine structure analysis reveals the local structure of Eu in the PNCs. We propose that the cation-solvent interaction strongly influences the crystallization process of ternary Cs x Pb y Br z , and the formation of Eu-solvent complexes further modifies the PNCs surface resulting in unique luminescence properties.