Synthesis of cauliflower-like ZnO–TiO2 composite porous film and photoelectrical properties

A series of cauliflower-like TiO2–ZnO composite porous films with various molar ratios of Zn/Ti were prepared by the screen printing technique on the fluorine-doped SnO2 (FTO) conducting glasses. The composite films were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray energy-dispersive spectrometry (EDS) and UV–vis transmittance spectrum. The results showed composite film electrode had a novel cauliflower-like morphology, which could effectively increase the dye absorption. The corresponding dye-sensitized solar cells (DSCs) were made by the composite film, and effects of ZnO incorporation on the photovoltaic performances of the DSCs were studied. With the Zn/Ti molar ratio not more than 3% in ZnO–TiO2 composite film of about 5 μm-thickness, the photocurrent density (Jsc) and the solar-to-electricity conversion efficiency (η) were greatly improved compared with those of the DSC based on bare TiO2 film of same thickness. This increases in efficiency and Jsc were attributed to high electron conductivity of ZnO, the improved dye adsorption and large light transmittance of composite film.