Zn（O,S）（zinc oxysulfide） is an important chalcogenide material recently reported to be potentially applied as electrode buffers in thin film solar cells. Both vacuum and solution approaches have enabled the fabrication of Zn（O,S） films. However they either require extreme conditions and high energy consumption for synthesis, or suffer from lack of controllability mainly due to the thermodynamic and kinetic distinction between Zn O and Zn S during film growth. Here we demonstrated an effective electrodeposition route to obtain high-quality Zn（O,S） thin films in a controllable manner. Importantly, tartaric acid was employed as a secondary complexing agent in the electrolyte to improve the film morphology, as well as to adjust other key properties such as composition and absorption. To elucidate the vital role that tartaric acid played, thermodynamic and kinetic processes of electrodeposition was investigated and discussed in detail. The accumulative contribution has shed light on further exploit of Zn（O,S） with tunable properties and optimization of the corresponding electrodeposition process, for the application in thin film solar cells.
