Chalcogen Incorporation in Cu-Sn-S Absorbers: Structural, Optical, and Photovoltaic Performance of Simulation-Guided CTS and CTSSe Solar Cells

This work presents a comprehensive experimental, simulation, and device performance comparative study of sustainable thin-film photovoltaic absorbers, Cu2SnS3 (CTS) and Cu2Sn(S, Se)3 (CTSSe). The CTS and CTSSe films were synthesized from a dip-coated Cu-Sn-S precursor layer followed by sulfurization and selenization processes, respectively. Structural analysis confirms the formation of a monoclinic phase in both films, while selenium incorporation promotes significant grain growth in CTSSe films. Both absorbers exhibited high optical absorption coefficient (α > 10⁵ cm⁻¹) and suitable band gaps (1.0–1.6 eV) for photovoltaic applications. Furthermore, numerical device simulations were used to evaluate the photovoltaic performance of CTS and CTSSe-based absorbers. Device simulations combined with experimental analysis identified 475 ℃ as the optimal annealing temperature. Based on these simulation results, prototype devices were fabricated, obtaining commendable efficiencies of 2.2% and 3.0% for CTS and CTSSe based devices, respectively.