Intrinsic defects in B-site columnar-ordered halide double perovskites Cs₂AgPdBr₅

Cs₂AgPdBr₅ is a new type of double perovskite with one-dimensional electronic dimensionality, which is expected to be a promising candidate of photovoltaic materials. Considering that defects usually exist in real materials, in this study, we investigate the intrinsic defect properties of Cs₂AgPdBr₅ from first principles. First, the phase diagram of Cs₂AgPdBr₅ is calculated. It turns out that its thermodynamic stable region is small, suggesting that the growth conditions should be carefully controlled to obtain high-quality samples. By systematically investigating the Fermi-level pinning behavior, we find that p-type Cs₂AgPdBr₅ can be obtained at an Ag-poor condition. At the same time, Pd2+i and Pd1+Ag are the only two deep-level recombination centers at 300 K. Therefore, if possible, the amount of palladium should be relatively small in the synthesis process. Our study provides guidance to obtain high-performance Cs₂AgPdBr₅ materials for photovoltaic applications.