First‐Principle Density Functional Theory‐Derived Nonleaded KSn1−xGexI3‐Based Perovskite Solar Cells: A Theoretical Study

The lead toxicity and instability of conventional all‐inorganic lead halide perovskites hinder the production of efficient and stable nontoxic perovskite solar cells (PSCs), which prompts the search for viable nonleaded substitutes for photovoltaic (PV) applications. The present study investigates the optoelectronic characteristics of proposed lead‐free orthorhombic perovskites KSn 1− x Ge x I 3 ( x = 0, 0.5, 1) via first‐principle density functional theory (DFT), to get an insight into their PV applicability. DFT computation with generalized gradient approximation of Perdew–Burke–Ernzerhof exchange–correlation is performed to extract the parameters such as bandgap, mobility, dielectric constant, conduction band minima and valence band maxima of KSnI 3 , KSn 0.5 Ge 0.5 I 3 , and KGeI 3 to demonstrate their capability as a functional layer in PSCs. These characteristics have been utilized to simulate PSCs. The simulated devices FTO/SnO 2 /KSnI 3 /Spiro‐OMeTAD/Au, FTO/SnO 2 /KSn 0.5 Ge 0.5 I 3 /Spiro‐OMeTAD/Au, and FTO/SnO 2 /KGeI 3 /Spiro‐OMeTAD/Au exhibit the efficiency of 8.23%, 8.89%, and 4.12%, respectively. Thereafter, the most effective KSn 0.5 Ge 0.5 I 3 ‐cell with an efficiency of 8.89% is selected for additional optimization of thickness, defect density, and doping concentration to achieve maximum efficiency. The distinctive green proposes KSn 0.5 Ge 0.5 I 3 ‐PSC, with an optimized efficiency of 20.29% stands out among the top PSC technologies. Future research on this subject will focus on synthesizing the proposed novel KSn 0.5 Ge 0.5 I 3 ‐PSC and evaluating the performance of the KGeI 3 ‐PSC.