Structural and optoelectronic behavior of the copper-doped Cs2AgInCl6 double perovskite: A density functional theory investigation

Recently, direct bandgap double perovskites are becoming more popular among photovoltaic research community owing to their potential to address issues of lead (Pb) toxicity and structural instability inherent in lead halide (simple) perovskites. In this study, In-Ag based direct bandgap double perovskite, Cs2AgInCl6 (CAIC), is treated with transition metal doping to improve the optoelectronic properties of the material. Investigations of structural and optoelectronic properties of Cu-doped CAIC, Cs2Ag(1-x)CuxInCl6, are done using ab-initio calculations with density functional theory (DFT) and virtual crystal approximation (VCA). Our calculations show that with increasing Cu content, the optimized lattice parameter and direct bandgap of Cs2Ag(1-x)CuxInCl6 decrease following linear and quadratic functions respectively, while the bulk modulus increases following a quadratic function. The photo-absorption coefficient, optical conductivity and other optical parameters of interest are also computed, indicating enhanced absorption and conductivity for higher Cu contents. Based on our results, transition metal (Cu) doping is a viable means of treating double perovskites - by tuning their optoelectronic properties suitable for an extensive range of photovoltaics, solar cells and optoelectronics.