Cu3BiS3 as a potential photovoltaic absorber with high optical efficiency

Cu3BiS3 is a potential photovoltaic material. Employing a first-principles approach, we calculate the structural, electronic, and optical properties of Cu3BiS3, and we demonstrate that Cu3BiS3 is an indirect band gap semiconductor in contrast to similar chalcogenide semiconductors. The fundamental band gap energy is estimated to be Eg ≈ 1.5–1.7 eV. The analysis reveals that Cu3BiS3 has a much stronger absorption coefficient (>105 cm−1) compared to other Cu-S based materials like CuInS2 and Cu2ZnSnS4. This is explained by the presence of localized Bi 6p states in the band gap region, generating a flat lowest conduction band.