Exciton‐Resolved Electrical Simulation of PBDB‐T:ITIC Organic Solar Cells: Effects of Active‐Layer Thickness and Charge Mobility

A coupled optical–electrical simulation framework is developed for PBDB‐T:ITIC organic solar cells (OSCs) by integrating exciton‐resolved optical modeling with SCAPS‐1D device simulations. In contrast to conventional approaches that assume direct conversion of absorbed photons into free carriers, spatially resolved exciton generation profiles are obtained using transfer‐matrix optical calculations and converted into free‐carrier generation rates by explicitly accounting for exciton diffusion and dissociation. The model is applied to both conventional (ITO/PEDOT:PSS/PBDB‐T:ITIC/PFN‐Br/Al) and inverted (ITO/ZnO/PBDB‐T:ITIC//Ag) device architectures, revealing that the inverted structure exhibits higher power conversion efficiency and improved tolerance to transport limitations. The proposed framework enables consistent simulation of both broadband current–voltage characteristics and wavelength‐resolved external quantum efficiency (EQE) spectra by linking optical interference effects with exciton dynamics and charge transport. Comparison with experimentally reported – and EQE characteristics shows good agreement, validating the physical consistency of the approach. These results highlight the importance of incorporating exciton‐resolved photogeneration for realistic modeling and design of high‐performance OSCs.