Roughness-Controlled Cu2ZnSn(S,Se)4 Thin-Film Solar Cells with Reduced Charge Recombination

Copper zinc tin sulfo-selenide (CZTSSe) is a promising light-absorbing material of thin-film solar cells because of its low material cost especially when it is prepared by cost-effective processes like the electrochemical deposition process. The CZTSSe thin-film solar cells, however, suffer from the relatively low efficiency, mostly because of the significant charge recombination. Given that the surface recombination is one of the major recombination paths, controlling the surface roughness, and thus the interfacial area is one of the key factors for improving their device performances. In this study, we demonstrated a simple but effective strategy for reducing the surface roughness during the electrochemical deposition process of the CZTSSe thin films. By adopting an initial nucleation stage with higher deposition currents ahead of the steady-state galvanostatic deposition, the surface …