Understanding the electronic, structural, optical, photovoltaic and thermoelectric properties of Cs2GeSnBr6 by first-principles and SCAPS-1D simulation

The electronic, optical, structural, thermoelectric and photovoltaic properties of Cs2GeSnBr6 are investigated by using density functional theory and SCAPS-1D simulation. There is a lack of imaginary frequency in the phonon dispersion band structure implies that Cs2GeSnBr6 is stable against lattice distortion. Also, Goldsmith tolerance factor (τ), octahedral factor (µ), and convex-hull calculations demonstrated that Cs2GeSnBr6 can be synthesized. In addition, electronic band structure calculation using GGA-PBE+mBJ+SOC shows that Cs2GeSnBr6 has a direct band gap value of 1.01 eV. Further, optical calculations revealed the higher value of absorption coefficient (α) and optical conductivity (σ) of Cs2GeSnBr6. Motivated by this, we have modelled the ITO/ZnO/Cs2GeSnBr6/Au photovoltaic cell which shows a maximum power conversion efficiency of 18.74%. Moreover, the obtained large ZT value Cs2GeSnBr6 which is originating from its good electrical conductivity with poor thermal conductivity.