Lead/lead-free based organic/inorganic absorbers such as our novel CS3Sb2Br9, CsSnGeI3 and MAPbI3 are studied to find an efficient absorber with better stability. The model validation for CsSnGeI3 shows a very good consistency. The numerical simulations are done with the help of SCAPS-1D having a planar structure as ITO/ETL/Absorber/HTL/Au for all three absorbers. TiO2 as ETL and Spiro-OMeTAD as HTL are used for simulation. The optimal thickness (defect density) for all three absorber are obtained as 1000 nm (1 × 1012 cm-3), 800 nm (1 × 1014 cm-3), and 1000 nm (1×1014 cm-3) for CS3Sb2Br9, CsSnGeI3 and MAPbI3, respectively. Finally, the maximum obtained power conversion efficiency (PCE) of CS3Sb2Br9, CsSnGeI3 and MAPbI3 are 15.69%, 15.89% and 15.95%, respectively. From the results, it can be concluded that our novel CS3Sb2Br9 shows the lowest short circuit current density (Jsc) but highest open circuit voltage (Voc) and quantum efficiency (QE) among all three PSCs. CsSnGeI3 followed nearly the same pattern as MAPbI3. Thus, the lead-free inorganic PSCs, CS3Sb2Br9 CsSnGeI3, express an efficient PCE in compare to lead based PSC, MAPbI3, with a significant improvements in terms of Jsc and fill factor (FF).