In this study, we explored the optimal performance of perovskite solar cells (PSCs) using the tin-halide material Rb2SnI6. This study focuses exclusively on the electrical properties of the devices, as simulated using SCAPS-1D software (solar capacitance simulator). The SCAPS-1D was employed to improve the device in the Rb2SnI6-based PSC, which utilized tungsten disulfide (WS2) as the electron transport layer and cadmium telluride (CdTe) as the hole transport layer (HTL). To identify the most suitable electron transport layer (ETL), we initially investigated WS2, SnS2, PCBM, and C60. The ITO/WS2/ Rb2SnI6/CdTe/Ni structure proved to be the most effective ETL after extensive investigation, demonstrating a power conversion efficiency (PCE) of 24.95%, a Voc of 1.0896 V, a Jsc of 44.6795 mA cm2, and an FF of 82.71%. Subsequently, we evaluated the impact of the absorber thickness, ETL thickness, and defect density on the device’s effectiveness in the Rb2SnI6, WS2, and CdTe layers. We further investigated the effect of adjusting the interfacial defect densities at the CdTe/Rb2SnI6 and Rb2SnI6/WS2 interfaces to optimize the device’s capabilities further. Additionally, we examined the proposed PSC’s quantum efficiency (QE), current density–voltage (J-V), shunt resistance, series resistance, capacitance–voltage, working temperature, and generation-recombination parameters. The results of these simulations provide valuable information for the excellent scientific fabrication of an inorganic PSC that is based on Rb2SnI6.