| Dye-Sensitized Solar Cells (DSSCs) have attracted extensive attention due to its low cost, simple fabrication process and plentiful sources. Now the optimum photoelectric conversion efficiency of DSSC is far lower than its theoretical value. Photoanode as an important component of DSSC has direct effects on the eff of DSSC. In this paper, ZnO/TiO2 composite based DSSC was studied. Self-assembly ZnO microspheres consisting of nanosheet were prepared by using urea and zinc nitrate as raw material through hydrothermal method, ZnO/TiO2 composite powder prepared by hydrothermal method and mechanical mixing method and ZnO/TiO2 core-shell structure powder prepared by simple dipping method were seperately used as photoanod material in DSSC. XRD、SEM、TEM、XPS and EDS were carried to characterize ZnO/TiO2 powder and photoanode. The I-V curves, IPCE and EIS of the DSSCs fabricated by different photoanode films were tested. The main results were as following:(1) When the molar ratio of urea to zinc nitrate was 3:1, ZnO microspheres with diameter of 15～20μm formed by ZnO nanosheet with 25nm thickness was obtained by hydrothermal method. The ZnO microsphere was milled after vortex ultrasonic dispersed to prepare slurry. The Voc,Jsc, FF and Eff of the DSSC fabricated by the photoanode with thickness of 34.33μm were 0.65 V,11.50 mA/cm2,0.63 and 4.82%, respectively. The electronic life time was 8 ms.(2) TiO2 and ZnO/TiO2 powder were prepared by hydrothermal method. The sythesized TiO2 powder with hierarchical nanosphere structure was consistied of 15-20nm TiO2 particles. The particle size of the hierarchical nanosphere was nonuniform, ranging from 5 to 8μm. The morphologies of the powder varied with the ratio of n(Zn2+):n(Ti4+). The Jsc and Eff of the DSSC based on the TiO2 microsphere photoanode were 1.77 mA/cm2 and 0.9%, respectively. When the ratio of n(Zn2+): n(Ti4+) was 1:1, the Jsc and Eff of the DSSC fabricated by ZnO/TiO2 powder were optimum, which were 2.88 mA/cm2 and 1.26%, respectively. With the ratio of n(Zn2+): n(Ti4+) increasing, the Eff decreased.(3) The average particle size of ZnO nanoparticles prepared by alcohol-thermal method were about 25-35 nm. The particle size of TiO2 prepared by hydrothermal method was 30-40 nm. The Eff, Voc, Jsc and FF of the DSSC based on the TiO2 were 7.95%,0.74 V,15.21 mA/cm2 and 0.71, respectively. When the addition amount of ZnO was 2 wt%, the electronic life time (τn) was optimum, achieving 3.9ms. The Voc, Jsc, FF and Eff of the DSSC were 0.76 V,16.21 mA/cm2,0.78 and 9.54%, respectively. The eff compared to that of DSSC based on pure TiO2 improved 20%.(4) By simple immersing ZnO poweders into butyl alcohol solution of tetrabutyl titanate (TBOT), TiO2 nanoparticles were well decorated onto ZnO nanocrystal surface. When the concerntration of tetrabutyl titanate butanol was 0.5 M and dye immersion time was 2 h, and the DSSC fabricated by the ZnO/TiO2 core-shell structure photoanode showed an optimum Jsc and Eff, which were 5.01 mA/cm2 and 2.77%, respectively. The Eff improved 48% compared to 1.87% eff of DSSC prepared by pure ZnO nanoparticles. |
PDF Full Text Request