First principle comparative study of transitional elements Co, Rh, Ir (III)-based double halide perovskites

The transitional elements Co, Rh, Ir(III)-based double halide perovskites Cs2AgMX6(M=Co, Rh, Ir; X = Cl, Br, I) were studied by first principle calculation. The structural stability analysis was carried out through the tolerance factors, formation energy and formation enthalpy. The elastic constants further confirm the mechanical stability and demonstrate the ductile and ionic nature of materials. The electronic band structures indicate that all materials are either direct or quasi-direct bandgap semiconductors, and their band gap value varies from 0.783 eV to 2.418 eV. The optical properties especially the absorption coefficient prove the broad light response in the UV-visible-IR region. In conclusion, Cs2AgCoBr6 was considered as the candidate for optoelectronic application such as solar absorber, due to its appropriate band gap, ductility and broad light absorption.