CuSbS2 and CuBiS2 as potential absorber materials for thin-film solar cells

Abstract

The current thin-film photovoltaic (PV) technologies are dominated by CdTe and Cu(In,Ga)Se2 compounds. However, due to the limited availably and toxicity of the elements in these technologies, the current research efforts are directed to search alternative earth abundant materials. Therefore, in this work, we analyze the CuSbS2 and CuBiS2 compounds as alternative absorber materials for future thin-film solar cells. Employing a first-principles approach within the density functional theory, we calculate the structural, electronic, and optical properties of CuSbS2 and CuBiS2 compounds. We show that these compounds have indirect fundamental band gap Eg ≈ 1.5–1.7 eV. The indirect gap nature is different from the previous experimental measurements. However, due to the flat bands, the direct gap Egd ≈ 1.6–1.8 eV is suitable for solar energy technologies. Furthermore, calculations reveal that these compounds have strong absorption coefficients, which are about twice as large as in other Cu-S based PV materials like CuInS2 and Cu2ZnSnS4. Therefore, CuSbS2 and CuBiS2 have the potential to be used as absorber materials in thin-film PV technologies.