The performance of the donor and acceptor doping in the Cu-rich Cu2ZnSnSe4 bulks with different Zn/Sn ratios

•Cu-rich Cu2ZnSnSe4 pellets at different Zn/Sn ratios were reactively sintered.•Discrepancy in the as-expected lattice parameter is explained.•The non-linear change in carrier concentration is related to point defect.•Defect is explored by studying the systematic changes in composition.

The concept of defect chemistry is applied to investigate the defects in the Cu-rich Cu2ZnSnSe4 (CZTSe) bulks liquid-phase sintered at 600 °C with soluble sintering aids of Sb2S3 and Te. The electrical property and lattice parameter changed with the Zn/Sn ratio were used as gauges to evaluate the type and concentration of point defects. Sn4+ acts as a donor to form the n-type semiconductor for the Sn-rich CZTSe. At the Zn/Sn ratio of 1.0, Cu-rich CZTSe is p-type with the high hole due to the Cu antisite defect and the B-site vacancy. With increasing the Zn ratio, more Zn2+ ions will move to the Cu1+ site to act as antisite donor to counter-balance the increase in the hole concentration and to have the lattice parameter smaller.