Iodide Vacancy Defects Clustering in Pairs Rather Than in Isolation in a Lead Iodide Perovskite: Identification, Origin, and Implications
Xiangxiang Feng, Yunhao Li, Biao Liu, Chuan‐Jia Tong, Mengqiu Long, Meng‐Qiu Cai, Junliang Yang
Abstract
Iodide (I – ) vacancy defects are strongly related to the stability of perovskite optoelectronic devices. The I – vacancy in lead iodide perovskites is normally considered to exist in the form of a single isolated defect. However, we determined that the I – vacancies cluster in pairs in specific ways in the typical perovskite of tetragonal CsPbI 3 . This I – vacancy–vacancy dimer is energetically more favorable than two isolated I – monovacancies. It breaks the symmetry of the Pb–I octahedron, resulting in lattice distortion. Its origin lies in the special lattice distortion effect caused by the electron orbital interaction of the perovskite material. Furthermore, the I – vacancy–vacancy dimer and the associated lattice distortion increase the carrier lifetime by 1.3 times compared to that of the system with two isolated I – monovacancies, but they also compromise its structural stability. This new insight into the I – vacancy defect will enhance our understanding of perovskite optoelectronic devices.