Analysis of the electronic structures of 3d transition metals doped CuGaS₂ based on DFT calculations

3d transition metals doped CuGaS₂ are considered as possible absorbing material candidates for intermediated band thin film solar cells. The electronic structure and optical properties of 3d transition metals doped CuGaS₂ are investigated by using density functional theory calculations with the GGA + U method in the present work. The doping with 3d transition metals does not obviously change the crystal structure, band gap, and optical absorption edge of the CuGaS₂ host. However, in the case of CuGa_1−xTM_xS₂ (TM = Ti, V, Cr, Fe, and Ni), there is at least one distinct isolated impurity energy level in the band gap, and the optical absorption is enhanced in the ultraviolet-light region. Therefore, these materials are ideal absorber material candidates for intermediated band thin film solar cells. The calculated results are very well consistent with experimental observations, and could better explain them. (semiconductor materials)