A strategy to enhance the efficiency of dye-sensitized solar cells by the highly efficient TiO2/ZnS photoanode

Abstract

In dye-sensitized solar cells (DSSCs), the TiO₂ photoanode film plays an important role in increasing the power conversion efficiency. In this work, TiO₂ nanoparticles were first coated on fluorine-doped tin oxide by the doctor-blade method, and then a thin film of zinc sulfide (ZnS) was successfully fabricated on the surface of the TiO₂ nanoparticles using the successive ionic layer adsorption and reaction method. The performance of the DSSCs was examined in detail using a cobalt sulfide counter electrode and I⁻/I₃⁻ electrolyte. X-ray diffraction and energy dispersive X-ray spectroscopy measurements were used to find the composition of the films. Characterization with electrochemical impedance spectroscopy indicated that the recombination rate decreased drastically during the electron transportation. The DSSCs based on ZnS coated TiO₂ photoanode achieved a power conversion efficiency of 5.90% under 1 sunlight illumination, which is higher than that of the bare TiO₂ photoanode (4.43%). This suggests that the promising ZnS-coated TiO₂ nanoparticles accumulate a large number of photo-injected electrons in the conduction band of the photoanode and the N719 dye lowers the recombination of photo-injected electrons with the redox electrolyte.