Utilizing Solvent Repulsion between Dimethylformamide and Isopropanol to Manipulate Sn Distribution for Bifacial CuZnSn(S,Se) Solar Cells.

Rationalizing the role of chemical interactions in the precursor solutions on the structure, morphology, and performance of thin-film CuZnSn(S,Se) (CZTSSe) is key for the development of bifacial and other photovoltaic (PV) device architectures designed by scalable solution-based methods. In this study, we uncover the impact of dimethylformamide (DMF) and isopropanol (IPA) solvent mixtures on cation complexation and rheology of the precursor solution, as well as the corresponding morphology, composition, and PV performance of CZTSSe thin-film grown on fluorine-doped tin oxide (FTO). We find that increasing the proportion of IPA leads to a nonlinear increase in dynamic viscosity due to the strong repulsion between DMF and IPA, which is characterized by an interaction cohesion parameter of 3.

Correlating Molecular Precursor Interactions with Device Performance in Solution-Processed CuZnSn(S,Se) Thin-Film Solar Cells.

Research efforts aimed at improving the crystal quality of solution-processed CuZnSn(S,Se) (CZTSSe) absorbers have largely employed delicate pre- and postprocessing strategies, such as multistep selenization, heat treatment in mixed chalcogen atmospheres, and multinary extrinsic doping that are often complex and difficult to reproduce. On the other hand, understanding and tuning chemical interactions in precursor inks prior to the thin-film deposition have received significantly less attention. Herein, we show for the first time how the complexation of metallic and chalcogen precursors in solution have a stark influence on the crystallization and optoelectronic quality of CZTSSe absorbers.

Ge-doping of CZTS nanocrystals and CZTSSe solar absorber films.

CuZnSn(S,Se) (CZTSSe) is a promising material for thin-film photovoltaics, however, the open-circuit voltage () deficit of CZTSSe prevents the device performance from exceeding 13% conversion efficiency. CZTSSe is a heavily compensated material that is rich in point defects and prone to the formation of secondary phases. The landscape of these defects is complex and some mitigation is possible by employing non-stoichiometric conditions.