Understanding the Effect of Intrinsic Defects in Lead-Free Vacancy-Ordered Double Perovskites Cs2PdBr6

Vacancy-ordered double perovskites, the variant of metal-halide perovskites, have excellent potential for use in optoelectronic and thermoelectric devices. A narrow region of forming the stable vacancy-ordered double perovskite Cs2PdBr6 by the chemical potential calculation via the first principles method was reported. Perdew–Burke–Ernzerhof functionals were used to investigate the possible intrinsic defects and the corresponding formation energy of Cs2PdBr6. Under the Pd-rich condition, the VBr defect was spontaneously formed as it has the lowest formation energy among all donor defects. In contrast, the sample became a p-type conducting material with a high hole concentration under the Pd-poor condition. This indicates that the defect-induced decline of photoelectric properties of Cs2PdBr6 can be alleviated by regulating the VBr defect alone. Finally, the Cs2PdBr6 microcrystals were fabricated via hydrothermal synthesis. In addition, XRD, PL, and Raman spectroscopy were also performed on Cs2PdBr6 powder to characterize the microstructure and optical properties of the compound; the results showed that VBr defects can be formed spontaneously, which is consistent with our theoretical calculations.