Computational Insights into the Structural and Optical Properties of Ag-Based Halide Double Perovskites

Lead-free halide double perovskites (HDP) have attracted enormous attention in recent years due to their low toxicity, excellent stability, tunable optical properties, and extensive range of compositional possibilities they present. In the very broad HDP family, Ag-based materials are of particular interest due to their easy synthesis, stability to light and moisture, and interesting optical properties, especially in the form of nanocrystals. Given the very large compositional space, theoretical studies play a crucial role in providing insights into the most promising dopant and possible defect interactions to guide the synthesis and explain the properties. In this review, we discuss recent theoretical works on Ag-based perovskites with an emphasis on density functional theory (DFT) calculations. The computational methods and tools are evaluated, assessing their relative strengths and limitations in their ability to clarify experimental results. We focus specifically on how lattice defects influence the structure and properties of HDP, including lattice and thermodynamic stability, band gap tuning, and photoluminescence.