TiO2/ZnO composite thin film was prepared by sequentially spread TiO2and ZnO thin film on the ground layer by layer with sol-gel method respectively. Two different natural dyes (Hehuang safflower yellow pigment and Lycium ruthenicum Murr pigment) were used as sensitizer respectively to sensitize TiO2/ZnO thin film photoanodes and be assembled into solar cells. Dipping time of photoanodes stayed in sensitizer was investigated systematically and the results show that higher photovoltaic conversion efficiency can be obtained with extension of immersing time. The phase structure, crystallinity, morphology and optical property of photoanode were characterized based on XRD, SEM and UV-vis measurements.

Pure phase of Yb3+/Er3+ co-doped β-NaYF4 micron tubes with up-conversion fluorescence were synthesized by hydrothermal method at 180°C for 24 hours. For better utilization of sunlight and improving photocatalytic efficiency of organic dyes, TiO2 nanoparticles were modified by combining with β-NaYF4 micron tubes to form TiO2/NaYF4 composite. Three different combination methods were studied and the photocatalytic activities of the corresponding samples were tested by measuring the degradation rate of rhodamine aqueous solution under illumination of simulated sunlight. The composite that TiO2 nanoparticles were well dispersed on the surface of NaYF4 shows better photocatalytic activity than other composites and was near twice efficiency of pure TiO2 nanoparticles. The reason may be due to the high activity of heterostructure for TiO2/NaYF4 composite that will make it easy for sunlight absorption and photocatalytic degradation.