HTL-Free Sb₂(S, Se)₃ Solar Cells with an Optimal Detailed Balance Band Gap

Antimony chalcogenides are widely studied as a light-absorbing material due to their merits of low toxicity, efficient cost, and excellent photovoltaic properties. However, the band gaps of antimony selenide (approximately 1.1 eV) and antimony sulfide (approximately 1.7 eV) both deviate from the optimal detailed balance band gap (∼1.3 eV) for terrestrial single-junction solar cells. Notably, the band gap of Sb₂(S, Se)₃ can be tunable in the range from 1.1 to 1.7 eV, which can cover the detailed balance band gap. In this work, the vapor transport deposition method with two independent evaporation sources is used to deposit Sb₂(S, Se)₃ thin films. By carefully optimizing the evaporation temperature and the start evaporation time of the Sb₂Se₃ and Sb₂S₃ sources, a suitable band gap of 1.33 eV is obtained. Finally, on the basis of the optimal Sb₂(S, Se)₃ films, Sb₂(S, Se)₃ solar cells without a hole transport layer achieved an efficiency of 7.03%.