Effects of the copper content on the structural and electrical properties of Cu2ZnSnSe4 bulks

We have investigated the concept of defect in CuxZnSnSe4 (x=1.6–2.0) and Cuy(Zn0.9Sn1.1)Se4 (y= 1.6–2.0) bulks prepared by liquid-phase sintering at 600 °C for 2 h with soluble sintering aids of Sb2S3 and Te. All samples were found to exhibit p-type semiconductor for CuxZnSnSe4, while n-type of behavior obtained at y= 1.8–2.0 for Cuy(Zn0.9Sn1.1)Se4 pellets. The Cu vacancy acts as an acceptor point defect to form the p-type semiconductor, and Sn4+ acts as a donor to form the n-type behavior for the Sn-rich CZTSe. SEM images of pellets show dense surface morphology, and increase in grain size upon Cu inclusion. The largely increased Hall mobility and the slightly changed carrier concentration for Cuy(Zn0.9Sn1.1)Se4 with increasing the Cu content is related to the types of its defects. At y=2.0 with carrier concentration of 4.88×1017 cm−3 showed the highest mobility of around 58 cm2/V s. Based upon the proposed point defects, the CZTSe property can be consistently explained.