Preparation and characterization of Cu [formula omitted]ZnGeSe [formula omitted] thin films by selenization method using the Cu–Zn–Ge evaporated layer precursors

Abstract

Cu 2 ZnGeSe 4 quaternary compounds are known to have a stannite structure and have band gaps suitable for optimum conversion efficiency for solar cells. We have prepared the Cu 2 ZnGeSe 4 thin films by the selenization method using the Cu–Zn–Ge evaporated layer precursors. The analyses of X-ray diffraction show that the single phase of Cu 2 ZnGeSe 4 is obtained by the selenization of precursors at 673–773 K. From the SEM observation of film surface, the grain sizes are larger to the order of 1– 2 μ m as the selenizing temperatures increase. The band gaps of selenized films by ten times sealed Se content are shown to be slightly narrower than those of bulk crystals (about 1.6 eV), but the optical band gap is close to 1.6 eV by decreasing the sealed Se content. These films have p-type conduction and electrical resistivities of about 0.1 Ω cm at room temperature. The rectification ratio of n-CdS/p-Cu 2 ZnGeSe 4 is more than two orders of magnitude.