Analysis of the Metallic Intermediate Band in Cr-doped AgGaS₂ Semiconductor for the Photovoltaic Application

Abstract

The intermediate band semiconductor of AgGa1-xCrxS2 is investigated by the first principles calculations and further confirmed by the experimental results. The band structures of pure and Cr-doped crystals were calculated and it is shown that the crystal with a direct energy band gap of about 0.95 eV for AgGaS2. Because of Cr dopant, a metallic intermediate band (IB) is successfully formed in the host. From the partial density of states (PDOS) of Cr-doped AgGaS2, the IB mainly comes from the hybridization of the Cr-3d and S-3p states. Based on the theoretical predications, the Cr-doped AgGaS2 is synthesized by the high-temperature solid state reaction. Two extra absorption responses are detected in the absorption spectra. The optical absorption coefficients are enhanced in the visible radiation range due to the formation of metallic and isolated IB. Therefore, Cr-doped AgGaS2 with an intermediate band is suggested as a potential material to enhance the efficiency of solar cells.