Alternative quaternary chalcopyrite sulfides (Cu2FeSnS4 and Cu2CoSnS4) as electrocatalyst materials for counter electrodes in dye-sensitized solar cells

• Physical characteristics of synthesized CFTS and CCTS nanoparticles were examined.
• CCTS was explored as a counter electrode for DSSCs for the first time.
• Electrocatalytic activity of the CCTS films was confirmed by cyclic voltammetry.
• Effect of elemental composition of prepared CE on DSSCs performance was examined.
• A photo conversion efficiency of 7.4% was obtained in DSSCs with CCTS based CE.

Quaternary chalcopyrite sulfides are attracting considerable interest as electrocatalysts for triiodide reduction in dye-sensitized solar cells (DSSCs). Conventionally, the much expensive platinum (Pt) is being used as an electrocatalyst material for counter electrodes (CEs) in DSSCs. The present study reports the synthesis of quaternary chalcopyrite sulfides (Cu2FeSnS4 (CFTS) and Cu2CoSnS4 (CCTS) nanoparticles for their application as alternative CE materials in DSSCs. For the first time, CCTS is being explored as a CE material for DSSCs. Physical properties such as crystal structure, elemental composition and morphological characteristics of the as synthesized nanoparticles and the sulfurized films are studied. Cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements demonstrated that the CCTS CE is more effective for tri-iodide reduction as compared to CFTS CE. The photo conversion efficiencies (PCEs) of DSSCs fabricated using CCTS and CFTS as CEs are found to be 7.4% and 7.1% respectively, while DSSC fabricated with Pt as the CE showed an efficiency of 8.2%. This indicates that they both can potentially be used as alternative CE materials in DSSCs in place of the more expensive Pt.