Catalytic activity enhancement of Cu2ZnSnS4 due to composite of Co9S8 as counter electrode for dye-sensitized solar cells

The catalytic activity of quaternary Cu 2 ZnSnS 4 (CZTS) as counter electrode (CE) of dye-sensitized solar cells (DSSCs) was enhanced by covering Co 9 S 8 on CZTS thin film prepared by the spin-coating method. The effect of the repeating number of spin coating process on morphologies and catalytic properties of CZTS thin films was investigated. When the repeating number of spin coating processes is 3, the CZTS thin film thickness is moderate and the formed nanoparticles are tightly bound. The conversion efficiency of DSSC based on the CZTS thin film CE prepared by 3 spin coating cycles reaches 4.79%. By forming a CZTS/Co 9 S 8 composite electrode via vulcanizing the deposited ZIF-67, the highest photoelectric conversion efficiency of DSSC based on the optimized composite CE further reaches 6.41%. The higher photoelectric conversion efficiency is attributed to the good interfacial transferring of electrons and redox properties for electrolyte of the composite CE. Graphical abstract