Ideal half-filled intermediate band position in CuGaS2 generated by Sb-related defect complex: a first-principles study

Cu-based chalcopyrite compounds have attracted much attention for photovoltaic application, while some of them (like CuGaS2) have energy gaps greater than the optimal value. An isolated and half-filled intermediate band located at the lower part of its original band gap exhibits in CuGaS2 with (Sb-Ga + Zn-Ga) or (Sb-Ga + V-cu) defect complex, in line with the intrinsic p-type conductivity of the host, revealed from our first-principles calculations. Subsequently, the absorption coefficients of CuGaS2 can cover the full solar light spectrum efficiently. Based on the defect formation energy calculations, however, these defect complexes are hard to reach a large concentration under equilibrium condition. Nevertheless, nonequilibrium growth methods are suggested to prepare samples inheriting the excellent adsorption coefficients. (C) 2019 The Japan Society of Applied Physics