Defect state and electric transport of the Cu-poor, Cu-rich, and In-rich Cu(In,Ga)Se2 bulk materials

Cu(In,Ga)Se2 (CIGSe) bulk material has been prepared by reactive liquid-phase sintering at 650 °C in the presence of Sb2S3 and Te sintering aids. The changes in contents of Cu in Cux(In0.7Ga0.3)Se2 (Formula 1) and In in Cu1−y(In0.7+yGa0.3)Se2 (Formula 2) has been done for the purpose of studying the influence of defect states on their electrical property. The Cu-rich CIGSe materials showed the higher mobility values with enhanced hole concentration, while the Cu-deficient CIGSe semiconductor had a lower carrier concentration. The p-type In-rich CIGSe bulks with carrier concentration (np) of 7.3 × 1016-3.4 × 1017 cm−3 and mobility (μ) of 3.2-4.8 cm2 V−1 s−1 have been achieved. The In excess can not only improve electrical properties by forming more InCu+2 donor defects but also mitigate the large anisotropic lattice shrinkage due to the Cu vacancy. The explanation of electrical properties for CIGSe material has been provided by its defect states and was consistent and supported by the data of lattice parameters.