Electrodeposition of Sn, In and Cu from Citrate Electrolytes

Abstract

Cu-In-Ga-Se (CIGS) and Cu-In-S (CIS) are photovoltaic absorber materials that can be fabricated by electrodeposition, and are commercially of interest for solar panels. A problematic limitation is that some of the components are costly and not abundant, such as In. Replacing all or part of the indium with Sn may be one alternative to reduce the need for indium. As a first step to codeposit Sn electrochemically with elements in CIGS and CIS photovoltaics a common, stable electrolyte must be developed; since the citrate complexing agent has been used with In reduction in other light adsorbing alloy systems, it is used here in our work. A comparison of Sn, In, InSn, and CuInSn codeposition onto planar electodes is presented. Results showed that the rates of Sn and In are enhanced when they are co-deposited from the same electrolyte. Also when Cu is present in the solution rather than as the substrate, the rate for In was enhanced, but only when Sn is present, suggesting a coupled reaction mechanism. Future work will focus on identifying the nature of the change in the reaction rates and codepositing indium and tin to ultimately create CI-Sn-S and CI-Sn-GS systems, to reduce the amount of indium needed.