A DFT engineering of double halide type perovskites Cs2SiCl6, Cs2GeCl6, Cs2SnCl6 for optoelectronic applications

Double halide type perovskites may be a game changer materials in optoelectronic technology in the near future because these materials are stable, reliable, compactable, and free the issues of toxicity observed in mostly lead based perovskite type halides. Herein, we will explore structural, optoelectronic, vibrational and thermodynamic, and mechanical properties based on DFT by using PBE + GGA and hybrid HSE06 functional to predict the applications of the double halide type perovskites Cs2SiCl6, Cs2GeCl6, and Cs2SnCl6 in optoelectronic and photovoltaic devices and related applications. The crystal structures of the considered materials are completely optimized and the observed energy band gap of the order of 3.2 eV, 3.32eV and 4.5 eV for Cs2GeCl6, Cs2SiCl6, and Cs2SnCl6, respectively. The mechanical stability of the studied materials has been observed by the criteria of Born stability, vibrational and thermodynamic stability has been confirmed due to no imaginary mode of phonon and by the negative formation of cohesive energy and enthalpy. In particular, the exceptional optical properties with large optical absorption, large dielectric constant, small reflectivity and good conductivity predict that the considered double halide type perovskites may be potential candidates for future optoelectronic devices and related applications.