Performance improvement of Cu2ZnSn(S,Se)4 solar cells by ultraviolet ozone treatment on precursor films

The precursor status is critical in obtaining high-quality CZTSSe absorbers for direct solution coating method. Here, the ultraviolet-ozone (UV-ozone) oxidation is introduced during precursor film preparation based on DMSO/DMF solutions. It was found that exposing precursor films in ultraviolet ozone with proper duration before selenization treatment effectively reduces the organic residues stemming from solvent and/or component sources. Comparing with the untreated reference sample, the crystallization and morphology of CZTSSe layers with UV-ozone treatment are evidently improved, leading to enhanced carrier lifetime and solar cell device performance. This work provides a feasible way to solve the common problem involving organic residues during CZTSSe layer preparation via a non-hydrazine solution process.