Different photocurrent response of CsPbBr particles.

Zero-dimensional (0D) all-inorganic cesium lead halide perovskites, particularly CsPbBr, have been attracting wide attention due to their excellent optical properties and stability. The research also focuses on the origin of green emission from CsPbBr, which has a bandgap located in the ultraviolet B (UVB) region. So far, both CsPbBr 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, CsPbBr 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 CsPbBr. From our calculations, numerous vacancies of Br are easier to appear in green-emissive CsPbBr 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 CsPbBr to some extent.