Influence of S-content ratios on the defect properties of Sb₂(S_x, Se_1–x)₃ thin-film solar cells

Sb₂(S, Se)₃ has widely emerged as an absorber material for solar cells because of its favourable optical properties and abundant raw materials. Although the Sb₂(S, Se)₃ film comprises simple binary elements and has a lesser complex phase than that of quaternary copper indium gallium selenide, the distribution of atoms within its structure significantly affects its performance. More specifically, this effect is attributed to three non-equivalent positions of selenium or sulphur atoms and two non-equivalent positions of antimony atoms inside its unique quasi-one-dimensional asymmetric structure. Consequently, the composition ratios inside Sb₂(S_x, Se_1–x)₃ significantly impact the film's properties, especially the defect properties. The underlying origins of this effect remain elusive. Along these lines, in this work, defect measurements of the Sb₂(S_x, Se_1–x)₃ solar cells with different S-content ratios were conducted using deep-level transient spectroscopy and then discussed in detail. The analysis confirmed that deep-level defects were always present, and their lower density favoured the device's performance. Moreover, the solar cells consisting of Sb₂(S_x, Se_1–x)₃ thin films with 0.3 S-content ratios exhibit better conversion efficiency with lower deep-level defects density and capture cross-section.