In situ solvothermal growth of Cu2ZnSnS4 thin film for counter electrode of dye-sensitized solar cells

Quaternary Cu2ZnSnS4y (CZTS) nanocrystalline thin films were in situ grown on FTO coated conductive glass by a low cost solvothermal method. The effect of the reaction time and the concentration of precursor solution on the purity and morphologies of the deposited thin films was studied. The morphology, crystal structure and composition of the deposited thin films were characterized by scanning electron microscope, high resolution transmission electron microscope, X-ray diffraction, Raman spectroscopy and energy-dispersive X-ray spectroscopy. The pure wurtzite CZTS nanoparticles can be formed as the reaction time is 20 h. The film prepared at the optimized precursor solution concentration has uniform thickness, smooth surface and tight binding between the nanoparticles. The performance of the deposited CZTS thin films used as the counter electrode for dye-sensitized solar cells (DSSCs) was evaluated by measuring photocurrent density-voltage curves of DSSCs, electrochemical impedance spectroscopies and Tafel polarization curves of the symmetric cells. Photoelectric conversion efficiency of DSSC based on the optimized CZTS counter electrode reached 6.19%. The excellent photoelectric performance is attributed to the better surface morphology and conductive skeleton of the prepared CZTS thin film. The in situ solvothermal preparation method of the CZTS thin films for counter electrode of DSSCs is green, low cost and simple.