Preparation and characterization of Cu2CoSnS4 thin films for solar cells via co-electrodeposition technique: Effect of electrodeposition time

Quaternary compound Cu2CoSnS4 (CCTS) is a potential candidate absorber layer in thin film solar cells. In this work the Cu2CoSnS4 (CCTS) thin film was synthesized by co-electrodeposition of Cu-Co-Sn-S precursors on Molybdenum substrate, followed by a high temperature (500 degrees C) sulfurization under Argon atmosphere. The effect of the electrodeposition time of CCTS precursors (Cu, Sn, Co, S) on the crystallographic structure, morphology, composition and optical band gap of CCTS thin films was investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and energy dispersion spectroscopy. From the results, it was found that the properties of the sample can be improved by decreasing the deposition time and we have found that as the deposition time increases, the amount of the secondary phase Cu2-xS increases. The elemental composition is enriched in Co and S and depleted in Cu with increasing time. The band gap was determined from diffuse reflectance and found for all films in the range of 1.4-1.5 eV.