<p>Global warming, caused by the excessive use of fossil fuels for electricity supply and the transportation industry, has forced countries to invest in renewable power generation systems. One of these solutions is solar cells. This study presents the design, simulation, and performance optimization of an advanced five-layer organic solar cell consisting of In₂O₃-SnO₂/MoO₃/P3HT: PC₆₁BM/ZnO/Al using a particle swarm optimization algorithm. Although particle swarm optimization has been widely used in photovoltaic studies, the novelty of this work lies in applying it within a coupled optical–electrical optimization framework for this five-layer organic solar cell, where the optical response of the active layer (absorption with reflection and transmission losses) and the electrical loss parameters (realistic series and shunt resistances in the diode-based model) are optimized simultaneously to enhance both power conversion efficiency and absorption bandwidth. Optical and electrical characterizations were performed to evaluate the light-matter interactions, current-voltage behavior, and power-voltage performance under standard conditions. Optical analysis showed high absorption with minimal reflection and transmission losses across the active layer, ensuring effective photon harvesting. Electrical modeling, based on the diode equation, incorporates realistic series and shunt resistances and allows for accurate extraction of photovoltaic parameters. The optimized device achieved a short-circuit current of 24.63&#xa0;mA, an open-circuit voltage of 1.188&#xa0;V, a fill factor of 65.58%, and a power conversion efficiency of 19.197%, which demonstrates competitive performance compared to recent advanced organic photovoltaics. The device has an absorption band that exceeds 214&#xa0;nm, representing 63% of the visible spectrum. The layer thickness plays a significant role in affecting efficiency, while power-voltage curves confirm the stability of maximum power point operation.</p>