Recently, organic-inorganic perovskite-based solar cells have become promising devices due to their unique properties in the photovoltaic field. However, the factor of toxicity, stability, high production cost and complicated fabrication processes of these devices is a challenge to their progress in commercial production. Here a numerical modelling of Caesium Tin-Germanium Tri-Iodide (CsSnGeI 3 ) as an efficient perovskite light absorber material is carried out. In this paper, different inorganic Hole Transport Materials (HTMs) such as Cu 2 O, CuI, CuSbS 2 , CuSCN and NiO have been analyzed with C 60 as the Electron Transport Material (ETM). We intend to replace the conventional hole and electron transport materials such as TiO 2 and Spiro-OMeTAD which have been known to be susceptible to light induced degradation. Moreover, the influence of the Electron Transport Layer (ETL) and the perovskite layer properties, bandgap, doping concentration and working temperature for various Hole Transport Layers (HTL) on the overall cell performance have been rigorously investigated. The design of the proposed PSC is performed utilizing SCAPS-1D simulator and for optimum device an efficiency greater than 30% was obtained. The results indicate that CsSnGeI 3 and C 60 are viable candidates for use as an absorber layer and electron transport layer in high-efficiency perovskite solar cells, with none of the drawbacks that other PSCs have.