Tuning processing parameters for enhanced performance in CsGeI₃ based perovskite solar cells: First principle calculations and SCAPS–1D

This study investigated all-inorganic lead-free CsGeI3-based perovskite solar cells (PSCs) using computational modeling. First-principles calculations determined their photoelectric properties and confirmed the application potential of CsGeI3 in the photovoltaic field. Density functional theory (DFT) studies determined their direct bandgap using PBE-GGA (1.564 eV) and TB-mBJ (1.570 eV) potential functions. Photon absorption was observed in the region with energies exceeding 2 eV. In addition, parameters such as optical conductivity, extinction coefficient, and energy loss function were measured. Device parameters, including defect density (Nt = 10¹⁵ cm^–1), absorber layer thickness (1100 nm), acceptor layer (N_A = 10¹⁹ cm^–1 series resistance (R_S= 1 Ω-cm²), and parallel resistance (R_Sh= 10⁶ kΩ-cm²), were optimized using SCAPS–1D simulations. The effects of environmental factors such as operating temperature (T = 300 K), solar radiation intensity, and 1 solar irradiance on device performance were investigated to understand the efficiency of the CsGeI₃ solar cell under practical conditions. After these optimizations, the device exhibited excellent power conversion efficiency (PCE) of 25.77%, short-circuit current density (Jsc) of 28.60 mA/cm², open-circuit voltage (V_OC) of 1.31 V, and fill factor (FF) of 81.62%. High efficiency was achieved by employing the TB-mBJ potential and optimized device fabrication parameters. The results highlight the important characteristics and functions of CsGeI₃ as the absorber layer (AL) in solar cells.