Thermally evaporated SnS absorber layers: Material characterization and integration into a core–shell solar cell

Tin monosulfide (SnS) is a promising earth-abundant absorber for next-generation thin film solar cells, yet its utilization in advanced device architectures remains limited. In this work, we investigate thermally evaporated SnS thin films as an absorber layer in a nanorod-based core–shell solar cell. Phase-pure orthorhombic SnS films grown on glass substrates exhibited flake-like morphology, strong visible-light absorption (E_g ≈ 1.33 eV) and p-type resistivity of 770 Ω·cm, confirming their suitability for photovoltaic applications. Systematic post-deposition annealing between 150 and 400 °C revealed that only moderate heat treatments induce limited microstructural relaxation, whereas higher annealing temperatures trigger sulfur loss, secondary-phase formation, band-gap widening and degradation of the optical response, thereby defining a narrow processing range for preserving high-quality SnS films. Exploiting the optimized as-grown films, a core-shell device with Glass/ITO/ZnO-NRs/CdS/SnS/Ag architecture was successfully fabricated. Vertically-well aligned ZnO nanorods (NRs) provided a large interfacial area and enhanced light harvesting for the conformal SnS absorber shell. The constructed core–shell solar cell exhibited a power conversion efficiency of 1.32% under AM 1.5 G illumination, which is the highest efficiency yet reported for SnS-based core-shell solar cells.