Regulating Air‐Annealing Time for Boosting the Performance of Cu 2 ZnSn(S, Se) 4 Solar Cells

Excellent morphology and low harmful defect states of the absorber layer are essential to fabricate the high‐performance Cu 2 ZnSn(S, Se) 4 (CZTSSe) devices. Herein, the annealing time of precursor films in air is proved to have much impact on the quality of absorber layer and the performance of devices. Appropriately extending the air‐annealing time can promote the diffusion of Na into films and O absorption on the surface of precursor films, boost the growth of crystal grain, and lessen the harmful defect density and band‐tailing states of absorber. The appropriate extension of air‐annealing time also regulates the electrical properties of the absorber. The efficiency of CZTSSe devices is enhanced from 6.92% (1 min) to 10.1% (7 min), with the decreased V OC, Def . These enhanced properties demonstrate that regulating the air‐annealing time of precursor films can be a simple and direct way for improving the performance of CZTSSe devices.