Pu Lei, Gu Yarong, Meng Qian, Pang Qi, Lu Aijiang, Zhao Lijuan
Materials Genome Institute, Shanghai University, Shanghai 200444, People's Republic of China.
School of Chemistry and Chemical Engineering, Guangxi University, Nanning, Guangxi 530004, People's Republic of China.
J Chem Phys. 2022 Jun 21;156(23):234702. doi: 10.1063/5.0095106.
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.
零维（0D）全无机铯铅卤化物钙钛矿，特别是CsPbBr，因其优异的光学性能和稳定性而备受关注。该研究还聚焦于CsPbBr绿色发光的起源，其带隙位于紫外线B（UVB）区域。到目前为止，无可见发射和有绿色发射的CsPbBr均已成功制备；然而，绿色发射的起源仍存在争议。光电流响应是探索光激发载流子如何影响材料光物理性质的有效方法之一。在我们的研究中，合成了无可见发射和有绿色发射的CsPbBr颗粒，并研究了它们的光电流响应。前者表现出正的光电流响应，而后者表现出负的光电流响应。这种负响应被认为是由于绿色发光的CsPbBr中带电激子构建的内建电场所致。根据我们的计算，大量的Br空位更容易出现在绿色发光的CsPbBr晶格中，这些空位可以与中性激子结合形成带电激子。这项工作可能在一定程度上有助于解释CsPbBr绿色发射的起源。
