Controlled synthesis and photoelectric application of ZnIn2S4 nanosheet/TiO2 nanoparticle composite films

This paper reports the controlled synthesis of ZnIn2S4 nanosheet/screen-printed TiO2 nanoparticle composite films by a facile hydrothermal method and demonstrates the photoelectric application of ZnIn2S4 nanosheets as potential inorganic sensitizers in semiconductor-sensitized solar cells. The ZnIn2S4 nanosheets with a thickness of about 20 nm and a lateral size of 2 mm were distributed not only on the surface but also in the interior of the TiO2 nanoparticles, indicating a full contact between ZnIn2S4 nanosheets and TiO2 nanoparticles. The ZnIn2S4/TiO2 composite films demonstrated bandgap energy values ranging from 2.38-2.64 eV and their peaks can shift from the ultraviolet region to the visible region, compared with that of the TiO2/FTO film (FTO: fluorine-doped tin oxide). The densities, thicknesses, morphologies of the ZnIn2S4 nanosheets could be controlled by adjusting the experimental parameters, including reaction times, temperatures and concentrations. The possible formation mechanism and growth process of the ZnIn2S4 nanosheets on the TiO2 nanoparticles were discussed based on the experimental results. Furthermore, as a proof-of-concept, ZnIn2S4/TiO2-based inorganic semiconductor-sensitized solar cells were fabricated by filling polysulfide liquid electrolyte into the electrodes and the device exhibited a reproducible photovoltaic response.