Perovskite solar cells have emerged as promising candidates for next-generation renewable energy technologies due to their high absorption coefficients, tunable bandgaps, and low-cost fabrication potential. Methylammonium lead iodide (MAPbI₃), one of the most studied perovskite materials, has demonstrated exceptional photovoltaic performance. However, challenges such as lead toxicity and long-term material instability continue to hinder commercial viability. Here, we discuss numerical simulation and optimization studies conducted using the SCAPS-1D program to optimize the architecture of single-junction, heterojunction, and tandem perovskite solar cells. The device structures were analyzed by varying the parameters of various perovskite absorber layers, hole transport layers, and electron transport layers to improve the power conversion efficiency and other critical performance metrics. To address concerns related to lead toxicity, the study explored lead-free alternatives such as MASnI₃, FASnI₃, etc., and discussed the reasons associated with their low efficiency and long-term stability as compared to the lead-based counterparts.