Performance Improvement of Cu2ZnSn(S,Se)4 Solar Cells by Introducing the Tiny Rare-Earth Ce3+

Controlling the formation of harmful defects plays an important role in obtaining high efficiency Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Here, the extra tiny Ce3+ is used to reduce the cation disordering of absorber, improving the performance of devices. Based on the ionic liquid-based solution approach, we prepared the different Ce-doped CZTSSe devices and studied the mechanism of trace Ce-doping. By means of XRD, SIMS, and EDS measurements, the incorporated Ce is found to be located at the grain boundaries in form of Na-Ce-Se phase. Further combined with the results of Raman, c-AFM, I-V, and EQE measurements, the trace Ce-doping is thought to limit the Sn-related defects of absorber and enhance the performance of devices from 6.77% (RCe = 0) to 9.14% (RCe = 0.024). Our conclusions will provide the new insights for further increasing CZTSSe-based solar cell efficiency by defect engineering.