Evaluating the effect of the substrate on the electrocatalytic performance of Cu2ZnSnS4 and Cu2ZnSnSe4 counter electrodes in dye-sensitized solar cells

•Copper zinc tin sulphide (CZTS)/selenide counter electrodes fabricated•Vitreous carbon, fluorine and indium tin oxide (ITO) substrates were compared•CZTS-ITO resulted in low series and charge transfer resistance•CZTS-ITO resulted in large current density and limiting diffusion current density•CZTS-ITO resulted in highest power conversion efficiency of 3.62% The colloidal synthesis of Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) nanoparticles and their application as counter electrodes in dye-sensitized solar cells (DSSCs). In particular, the effect of three substrates namely; vitreous carbon (VC), indium tin oxide (ITO), and fluorine doped tin oxide (FTO) on the electrocatalytic properties as well as the overall performance of the solar cells is investigated. The CZTS and CZTSe were synthesized and characterized with X-ray diffraction, Raman, X-ray photoelectron spectroscopy, Fourier transform infrared, nuclear magnetic resonance, and ultra-violet visible spectroscopies and transmission electron microscopy for the morphologies of the nanoparticles. The CZTS and CZTSe nanoparticles were quasi-spherical in shape with an average size of 7 ± 0.60 nm and 11 ± 0.84 nm, respectively. CZTSe on glassy carbon had better electrocatalytic activity as compared to CZTS however; the DSSCs from VC were poor due to the reduced transmittance of the substrate. On ITO and FTO, CZTS performed the best. Electrochemically, CZTS had the lowest series resistance and charge transfer resistance, however, had the largest exchange current density and limiting diffusion current thereby making it the best electrocatalyst. The DSSC using CZTS–ITO gave the best performance with the power conversion efficiency of 3.62%.