Band structure, photoelectric properties, and electronic transition mechanism of CuGa 1-x Ti x S 2 compound synthesized by solid-state reaction sintering method

As the optical absorption layer of solar cells, the intermediate band materials can extend the absorption spectrum. In this paper, an intermediate band material of CuGa 1-x Ti x S 2 compound is fabricated by a solid-state reaction sintering method. The CuGa 1-x Ti x S 2 compound shows a single-phase chalcopyrite structure. Partial replacement of Ga by Ti atoms introduces a narrow partially filled intermediate band, and two additional optical absorption edges located at 682 and 1075 nm. The carrier concentration of CuGa 1-x Ti x S 2 compound increases with the increase of Ti doping content, while the resistivity and mobility are decreased. The Fermi level passes through the intermediate band from the band structures of the samples. The presence of intermediate band leads to the increase of photo-induced carriers and the CuGa 1-x Ti x S 2 compound as an optical absorption layer material can be used as a candidate for high-efficiency solar cells. Graphical abstract The half-filled state and electronic transition mechanism are revealed from the band structure based on optical absorption