Time‐Efficient, Accurate, and Experimentally Grounded Optical Modeling of Multiscale‐Textured Thin‐Film Solar Cells

ABSTRACT Accurate prediction of optical performance in solar cells with multiscale‐textured interfaces is essential for optimizing light management in next‐generation photovoltaics. For the first time, a systematic validation of two complementary modeling approaches is carried out on experimentally fabricated thin‐film silicon (TF Si) solar cells: rigorous coupled‐wave analysis (RCWA), offering a full electromagnetic solution but constrained by boundary conditions, and a ray optics model, operating in the refractive regime. The study involves two device architectures: an a‐Si:H single‐junction cell on commercial Asahi VU‐type glass with random nanotextures, and an nc‐Si:H single‐junction cell on novel micro‐periodic honeycomb‐textured glass developed in‐house. Simulated and measured external quantum efficiency (EQE) and total front reflection losses (1‐R) are benchmarked using the root mean squared error (RMSE). The ray model shows deviations of only 2%–6%, comparable to RCWA, while reducing computation time from 1 week to less than 30 min. Applied to an a‐Si:H/nc‐Si:H tandem device on honeycomb‐textured glass, ray optics reproduced the optical response with spectral deviations below 6% and photocurrent mismatch under 0.2 mA/cm 2 . These findings uniquely establish ray optics, when combined with accurate optical constants and realistic interface morphologies, as a reliable and computationally efficient predictive tool broadly transferable to thin‐film technologies, including perovskites.