In this study, we reported the simulation study of lead-free all-perovskite tandem solar cell comprised of varied vacancy formation perovskite structure as wide bandgap absorber layer for FAMASnGeI3. The observations revealed that all-perovskite tandem solar cell of FTO/ZnO; 400 nm/Cs2AgBiBr6; 600 nm/FAMASnGeI3; 200 nm/Cu2O; 100 nm/Au achieved a notable PCE of 22.63 % at an operating temperature of 300 K with Jsc; 27.09 mA/cm2 Voc; 1.10 V and FF; 75.68 %. These findings suggests that this cell has strong potential in converting sunlight into electrical energy and indirectly will contribute to the advancement of environmentally friendly and high-performance solar cells, promoting the broader adoption of renewable energy technologies.