First-principles calculations to investigate the physical properties of lead-free double perovskites Cs2AgXCl6 (X=P, Co, As, Cd) for optoelectronic applications

In this work, we have been systematically studied the structural, electronic, optical, mechanical, and thermodynamic properties of double perovskite Cs2AgXCl6 (X= P, Co, As, Cd) by adopting first-principles calculations based on density functional theory (DFT). We found that the determined lattice parameters are in good agreement with the previously reported study, which are 7.518558 Å, 7.491051 Å, 7.370192 Å, and 7.517199 Å for Cs2AgAsCl6, Cs2AgCdCl6, Cs2AgCoCl6, and Cs2AgPCl6, respectively. The negative result of formation energy (ΔHf) indicates that these compounds are thermodynamically stable and can be experimentally synthesized. The electronic energy band structure indicates that Cs2AgXCl6 (X=P, Co, As, Cd) compounds are semiconductor behavior with the band gap (Eg) of 1.047 eV, 1.085 eV, 1.205 eV, and 2.074 eV for Cs2AgPCl6, Cs2AgCoCl6, Cs2AgAsCl6, and Cs2AgCdCl6, respectively. Electronic properties suggest that carrier transport is enhanced in Cs2AgXCl6 (X=P, Co, As, Cd) because of holes and electrons' small effective mass. Furthermore, optical properties suggest that these compounds have high absorption coefficients and low reflectivity values in the visible region. The structural and thermodynamic stability, the obtained energy band gap, tunable optical properties, and interesting thermodynamic properties indicate that Cs2AgXCl6 (X=P, Co, As, Cd) is a potential candidate in photovoltaic and optoelectronic applications.