<p>In this study, we investigated a solar cell with a lead-free inorganic double perovskite material, CS2AgBiBr6. Traditional lead halide perovskite solar cells have toxicity and stability issues. We used an organic hole transport layer (HTL), PEDOT:PSS, and two electron transport layers (ETLs), SnO2 and TiO2. The optimum parameters of the solar cells were obtained using the Solar cell Capacitance Simulator (SCAPS). The structure of the solar cell is ITO/SnO2/TiO2/CS2AgBiBr6/PEDOT:PSS/Au. We optimized the absorber layer thickness, and our results show that for a thickness of 2000&#xa0;nm, there is a high power conversion efficiency (PCE) value of 24.52.% In addition, the band-to- band radiative recombination effect was investigated for three radiative recombination coefficients, 10⁻⁸ cm³/s, 10⁻⁹ cm³/s, and 10⁻¹⁰ cm³/s. We calculated the open-circuit voltage, Voc, short-circuit current density, Jsc, fill factor (FF), and PCE and compared the photovoltaic parameters for different radiative recombination coefficients without considering the band-to-band radiative recombination. Furthermore, the effect of defect states in the active layer, ETL, and HTLs on the PCE has been expressed. We found that defects in the perovskite layer have a more drastic impact on the performance of the solar cells.</p>