Theoretical Insights of Degenerate ZrS2 as a New Buffer for Highly Efficient Emerging Thin‐Film Solar Cells

Abstract

SnS, Sb2Se3, Cu2SnS3, CuSb(S,Se)2, and Cu2BaSn(S,Se)4 are emerging as promising light absorbers for thin‐film photovoltaics due to their extraordinary optoelectronic properties. However, improper band alignment with the buffer and large open‐circuit voltage (VOC) deficit limits their power conversion efficiencies (PCE). Therefore, finding a suitable buffer that overcomes these obstacles is crucial. Herein, ZrS2 as an alternative buffer for the aforementioned emerging thin‐film solar cells using SCAPS‐1D is proposed. The important ZrS2 parameters are optimized, including bandgap, thickness, carrier concentration, and defect density. Interestingly, ZrS2 behaves as a degenerate semiconductor at carrier concentrations >1E17 cm−3, improving the conductivity of the solar cells; it also demonstrates a high defect tolerance nature when the defect density lies between 1E12 and 1E18 cm−3. After ZrS2 parameters optimization, the built‐in potential of SnS, Sb2Se3, Cu2SnS3, CuSb(S,Se)2, and Cu2BaSn(S,Se)4 solar cells is enhanced by 0.2, 0.58, 0.05, 0.42, and 0.3 V, respectively, reducing recombination rate. Upon optimizing absorbers parameters, a PCE > 35% for SnS, Sb2Se3, and CuSb(S,Se)2 while >32% for Cu2SnS3 and Cu2BaSn(S,Se)4 solar cells is accomplished with low VOC loss (≈0.1 V). The absorbers must have high carrier concentration (1E20 cm−3) and low defect density (1E14 cm−3) to achieve these PCEs.