Full inorganic cesium lead iodide (CsPbI3) HTL free transport layer is investigated and simulated using SCAPS. The aim of the study is to investigate the optimum performance of the device structure. Using DFT study, the optical refractive index and reflectivity of CsPbI3 are calculated. Further investigation of the device performance with changing parameters like metal back contact, absorber thickness, acceptor density, and defect density. The solar cell device has the optimum performance with Selenium as a back contact. The solar cell device structure of (FTO/ZnO/CsPbI3/Se) with Voc of 1.34 V, Jsc of 19.75 mA/cm2, an FF of 87.5%, and PCE of 23.25% are acquired for the proposed HTL-free CsPbI3-based PSC. The simulation study will be a guide in fabricating low cost highly efficient HTL free inorganic CsPbI3 solar cells.