Boosting the efficiency of solution- Based CZTSSe Solar Cells by Supercritical carbon Dioxide Treatment, a research article of Professor Wu's team, was published in Green Chemistry recently (Green Chem., 2020, 22, 3597, DOI: 10.1039/D0GC01355B. IF: 9.43, JCR-1).

Cu2ZnSn(S,Se)4 (CZTSSe) solar cells have been receiving considerable attention in recent years, owing to their low cost and toxicity as well as a high abundance of their constituent elements. Solution-based (mainly precursor solution) methods have been widely used in the fabrication of CZTSSe-based thin film solar cells. Though most record solar cells since 2009 have been achieved using solution-based methods, carbonaceous residues are always formed during post deposition treatment (PDT). These carbonaceous residues are detrimental to grain growth of CZTSSe to form large grains. The presence of unwanted small grain layers will increase the series resistance and reduce the fill factor of the solar cell, thus consequently decreasing the efficiency of CZTSSe solar cells.

In this work, Professor Wu propose “green” supercritical carbon dioxide (SCCO2) treatment to overcome the challenge of carbonaceous residues. The results confirm the reduction of carbonaceous residues in CZTSSe films through SCCO2 treatment. It can also effectively improve the film crystallinity and quality. Based on SCCO2 treatment, the efficiency of CZTSSe solar cell is successfully increased from 9.28% to 11.23%. In addition, this unique SCCO2 treatment may also bring forth new ideas for other solution-based optoelectronic devices.