Modification of CuSbS2 Photovoltaic Absorbent Properties via Defect Substitution

Abstract

CuSbS2 is an earth-abundant alternative absorbent material for thin-film solar cells. However, because of the comparable size of cations in CuSbS2 thin films, atomic disorder occurs, which modifies the Cu/Sb ratio and lowers the efficiency of the solar cells. A similar effect has been observed in previously reported absorbent materials, which could be reduced using extrinsic substitution defects. Although extrinsic substitution defects are crucial for resolving the disorder-related issues, they can strongly modify the structural, electronic, and optical properties of the CuSbS2 absorbent material, which may lower the efficiency of CuSbS2-based thinfilm solar cells. Therefore, herein, first-principle calculations were used to investigate structural, electronic, and optical properties of CuSbS2 with the Te-, Sn-, and Bi-substitution of Sb. The formation energies of the defects were calculated to investigate the stability of the defects at different charge states. Our results revealed that the absorption coefficient is strongly sensitive to structural distortions. Moreover, Sn+2Sb defects cause an indirect-to-direct band gap transformation, which can increase the efficiency of CuSbS2-based thin-film solar cells.