In this study, an all perovskite solar cell with CsSnI3 as HTM, MASnI3 as absorber layer and MAGeI3 as ETM is proposed. Our main aims are replacing costlier HTM and ETM with low-cost perovskite materials, designing highly efficient non-toxic perovskite solar cells and finding an alternative for expensive contact materials. Initially, the cell is simulated without optimizing the parameters and a PCE of 24.92%. However, the cell was not optimized, as the quantum efficiency of the cell is very low. Hence, the cell is simulated and optimized further to improve the efficiency. After optimizing the thickness, it was found that the optimal thickness for HTM is 0.025μm, ETM is 0.02μm, absorber is 0.315μm and the PCE have increased to 28.41%, which is 14% improvement. While doping density optimization have improved the PCE to 29.45% and the optimal doping density for HTM is 1×10 20 1/cm 3 , ETM is 1×10 17 1/cm 3 and absorber is 1×10 16 a/cm 3 . The cell is further tested with varying temperature and the cell can provide a PCE of 29.57% at 25 0 c. The cell is further optimized with series resistance and the cell can provide a PCE of 28.43% at 1Ω series resistance. Finally, the cell was optimized with contact materials. Four back contact materials can provide an optimized PCE of 28.28%, however the cost of Ni back contact is lower than other materials.