Revealing the role of intrinsic point defects in the stability of halide double perovskite Cs2AgBiBr6.

Abstract

An ab initio study of halide double perovskite (HDP) Cs₂AgBiBr₆ is presented. The antisites Br-2Cs and Bi+2Cs are found to be dominant acceptor- and donor-type defects, while the Bi_Cs defect exhibits a deep transition level to form electron traps and Br migration has the lowest activation barrier. Our work provides a fundamental understanding of defect physics and chemistry in HDPs, highlighting that the Br-rich condition is preferable for improving the photovoltaic performance and chemical stability.