Perovskite solar cells (PSCs) are improving in efficiency, but their stability remains a challenge compared to other solar technologies due to the use of hybrid organic–inorganic materials. To overcome this, researchers have shifted focus from methylammonium-based PSCs to more stable cesium (Cs)-based PSCs. By optimizing multi-layer structures to enhance solar spectrum absorption, substantial performance improvements are possible. In this study, we explored single (CsPbIBr2), dual (CsPbIBr2/KSnI3), and triple (CsPbIBr2/KSnI3/MASnBr3) absorber layer designs. The optimization of bilayer and triple-layer PSCs takes into account various factors, such as absorber layer thickness, defect density, and interface defect density for each PSC type. Finally, using the optimal triple-absorber layer combination, we optimized the electron transport layer, hole transport layer, series resistance, and shunt resistance. In this research, we attained impressive efficiencies of 34.22% for the triple-layer solar cell, 20.41% for the bilayer solar cell, and 7.32% for the single-junction PSC. This design approach led to an optimal configuration that showed substantial improvements over the experimental benchmark, including a 7.08% increase in open circuit voltage, a 256.9% increase in short circuit current, a 22.32% increase in fill factor, and a 367.5% increase in efficiency. By meticulously aligning multiple absorber layers in perovskite solar cells, we can unlock new pathways to developing highly efficient solar cells for the future.