Coupled optical and electrical modeling of TiO2 anti-reflective coatings for enhanced performance in GaAs thin-film solar cells

Optical reflection losses at the air--semiconductor interface limit the performance of gallium arsenide (GaAs) thin-film solar cells, whereas optical and electrical optimization are often considered separately. This study develops a coupled MATLAB-based optical--electrical simulation framework to evaluate the effect of titanium dioxide (TiO2) anti-reflective coating (ARC) thickness on GaAs thin-film solar cells. The optical response was assessed from wavelength-dependent reflectance, transmittance, absorptance, and quantum efficiency, and electrical performance was evaluated from current density--voltage characteristics, short-circuit current density ( Jsc), open-circuit voltage (Voc), fill factor (FF), and power conversion efficiency (PCE). TiO2 ARC thicknesses of 50, 75, and 100 nm were simulated under AM 1.5G illumination at 300 K. The 50 nm coating produced the lowest reflectance, highest absorptance, highest current density, and highest quantum efficiency across 300--900 nm. It also provided the best overall photovoltaic performance, with Jsc ≈ 34.7 mA cm-2, Voc approx 0.839 V, FF ≈ 0.842, and a maximum PCE of approximately 24.2%. Increasing the coating thickness to 75 and 100~nm reduced the PCE to approximately 22.95% and 21.85%, respectively. The results show that optimum photovoltaic efficiency requires a balanced combination of optical absorption, current generation, voltage, and FF. The coupled framework provides a computationally efficient tool for designing and optimizing ARCs for high-efficiency III--V photovoltaic devices.