Perovskite solar cells (PSCs) have drawn much attention in recent years due to their high efficiency at a lower cost. However, lack of stability restricts the wide use of PSC in modern technology. Reported literature shows, 2D perovskite material provides better tunability and a reduced number of defects in the crystal structure, leading to increased stability compared to 3D-perovskite. Although, 2D-PSCs still face challenges such as lower power conversion efficiencies compared to 3D perovskites and greater susceptibility to moisture and temperature changes. Therefore, ongoing research efforts are focused on improving the performance and stability of 2D perovskite solar cells. Furthermore, mixed-dimensional (2D/3D) perovskite solar cells are also expected to provide substantial stability and higher efficiency. This research is focused on optimizing the mixed dimensional (2D/3D) perovskite solar cells BA₂MA₂Pb₃I₁₀ and BA₂MA₂Pb₄I₁₃ as 2D and with MAGeI₃ as 3D perovskite, which results in a 27.15% and 27.58% increase in efficiency through the simulations handled by SCAPS-1D software. A detailed study of the structure and distinctive features of 2D and mixed dimensional 2D-3D perovskites has also been studied. Furthermore, the band alignment of 2D/3D perovskite solar cells has been studied by analyzing the structural and chemical composition. The effect of defect densities on 2D-3D mixed perovskites and on PSCs has also been presented.