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.