LAUSR

Recently, direct band gap double perovskites have become more popular among the photovoltaic research community owing to their potential to address issues of lead toxicity and structural instability inherent in lead halide (simple) perovskites. In this study, an In-Ag-based direct band gap double perovskite, ${\mathrm{Cs}}_{2}{\mathrm{AgInCl}}_{6}$ (CAIC), is treated with transition metal doping to improve the optoelectronic properties of the material. Investigations of the structural and optoelectronic properties of Cu-doped CAIC, ${\mathrm{Cs}}_{2}{\mathrm{Ag}}_{(1\ensuremath{-}x)}{\mathrm{Cu}}_{x}{\mathrm{InCl}}_{6}$, are done using ab initio calculations with density functional theory and virtual crystal approximation. Our calculations show that with increasing Cu content, the optimized lattice parameter and direct band gap of ${\mathrm{Cs}}_{2}{\mathrm{Ag}}_{(1\ensuremath{-}x)}{\mathrm{Cu}}_{x}{\mathrm{InCl}}_{6}$ decrease following linear and quadratic functions, respectively, while the bulk modulus increases following a quartic polynomial function. The photoabsorption coefficient, optical conductivity, and other optical parameters of interest are also computed, and the obtained spectra indicate enhanced optical properties at higher Cu contents. Based on our results, transition metal (Cu) doping is a viable means of treating double perovskites, by tuning their optoelectronic properties to be suitable for an extensive range of photovoltaics, solar cells, and optoelectronics.