Non-leaded, KSnI3 based perovskite solar cell: A DFT study along with SCAPS simulation

The commercialization of perovskite solar cells raises serious environmental concerns due to the presence of toxic lead. In the present work, we have studied a non-leaded perovskite, KSnI3 through density functional theory (DFT). The structural properties such as tolerance factor, octahedral factor, and formation energy of the orthorhombic structure of KSnI3 have been obtained to highlight its thermodynamic stability. The elastic con-stants and mechanical properties such as young's modulus, Poisson's ratio, and Pugh's ratio have been obtained to show its mechanical stability and ductility, which are desirable properties for the fabrication of thin films of the absorber layer. The optical properties of orthorhombic KSnI3 such as refractive index, absorption coefficient, dielectric function, optical loss factor, and reflectivity have been calculated to show its potential as an absorber material in perovskite solar cells (PSC). The density of states and band structure of orthorhombic KSnI3 have been calculated. The band structure has been utilized to obtain the effective masses of charge carriers, and a bandgap of 1.841 eV. The parameters of orthorhombic KSnI3 obtained through DFT have been used to simulate the performance of PSC. The performance of the perovskite solar cell has been optimized with respect to(w.r.t) its interface defect density, doping concentration, thickness, and defect concentration. The effect of series and shunt resistance on the performance of PSC has been studied. Finally, tungsten has been proposed as a budget-friendly replacement for gold as the back contact, and an efficiency of 9.776% is obtained. This study demonstrates the potential of a low-toxicity, lead-free, KSnI3 as an absorber material in perovskite solar cells.