Cesium lead iodide (CsPbI3) is widely employed as the absorber material for perovskite solar cells (PSC) with its excellent photothermal stability. Here, an electron transport layer (ETL)-free CsPbI3 PSC was modeled using the solar cell capacitance simulator (SCAPS) program. The simulation involves a series of parameters optimization, including the thickness, doping concentration, defect density and permittivity of the fluorine-doped tin oxide (FTO) electrode, the hole transport layer (HTL), and the perovskite (PVK) layer. Additionally, the defect density at the FTO/PVK interface and the PVK/HTL interface were considered. The study revealed that the power conversion efficiency (PCE) of the device is significantly affected by variations in the parameters of the PVK layer, especially the thickness and defect density. Moreover, the defect density at the contact interfaces also notably influences the device efficiency. After systematic computational optimization, the best device exhibited an open-circuit voltage (VOC) of 1.16 V, a short-circuit current (JSC) of 21.52 mA/cm², a fill factor (FF) of 87.83%, and a PCE of 21.9%, which is close to the full-structured device reported in experiment, demonstrating the potential of all inorganic PSCs with simplified structures.