Different photocurrent response of Cs₄PbBr₆ particles

Zero-dimensional (0D) all-inorganic cesium lead halide perovskites, particularly Cs₄PbBr₆, have been attracting wide attention due to their excellent optical properties and stability. The research also focuses on the origin of green emission from Cs₄PbBr₆, which has a bandgap located in the ultraviolet B (UVB) region. So far, both Cs₄PbBr₆ without visible emission and with green emission have been successfully prepared; however, the origin of green emission remains controversial. Photocurrent response is one of the effective approaches to explore how the photo-excited carriers influence the photo-physical properties of materials. In our study, Cs₄PbBr₆ particles without visible emission and with green emission were synthesized and their photocurrent response was investigated. The former showed a positive photocurrent response, while the latter showed a negative photocurrent response. The negative response was believed to be due to a built-in electric field constructed by the charged excitons in green-emissive Cs₄PbBr₆. From our calculations, numerous vacancies of Br are easier to appear in green-emissive Cs₄PbBr₆ lattices, which could combine the neutral excitons to form charged excitons. This work may contribute to the explanation of the origin of green emission of Cs₄PbBr₆ to some extent.