Preparation And Property Study Of Double-layer Composite Structure Photoelectrode In Dye-sensitized Solar Cell

Dye-sensitized solar cells (DSSCs), as a new type of photovoltaic technology, have attracted extensive attentions from both industry and academia due to its high efficiency, low-cost, light weight, easy fabrication process, and environmentally-friendly properties. Nano-sized TiO2film electrode, as one of the major components of DSSCs, has a very important influence on the photovoltaic performances. Electron injection and collection, light-harvesting efficiency, and unwanted electron recombination are all connected with the TiO2photoelectrode. In this thesis, valuable explorations have been carried out on the increase specific surface area of TiO2electrode, enhancement of light-harvesting, accelerating electrons transport and transfer, and lower electron recombination. We fabricated three new double-layer composite film electrode based on TiO2with different morphologies, and studied their applications in DSSCs. The main contents and results could be summarize as follows:(1) A novel TiO2double-layer (DL) composite film electrode based on TiO2hollow spheres (TiO2-HS) as overlayer and TiO2nanorod arrays (TiO2-RA) as underlayer was fabricated. The photoelectric conversion performances of DSSCs based on TiO2-RA film, TiO2-HS film, and TiO2-RA/TiO2-HS DL film were investigated, and their overall energy-conversion efficiency reaching0.99%,3.93%, and4.57%, respectively. The TiO2-RA/TiO2-HS DL film could improve the conversion efficiency of DSSCs owing to its synergic effects, i.e. the large specific surface area of TiO2-HS overlayer for effective dye adsorption, high light-harvesting capability of TiO2-RA film underlayer, and rapid interfacial electron transport in one-dimensional TiO2-RA.(2) Hierarchically sponge-like macro-/mesoporous TiO2(HSMM-TiO2) was prepared by hydrothermal method. The so-prepared HSMM-TiO2should be a good DSSCs electrode material, which show rapid electron transport and easy electrolyte diffuse properties. Furthermore, The HSMM-TiO2exhibited strong light scattering. In order to ensure good electronic contact between TiO2electrode and conducting glass, we introduced a TiO2nanoparticle underlayer between HSMM-TiO2overlayer and conducting glass. The resultant HSMM-TiO2/P25DL composite electrode achieved the highest conversion efficiency of5.48%, which is51.4%higher than that formed by P25nanoparticle film electrode (η=3.62%) and27.1%higher than that formed by HSMM-TiO2film electrode (η=4.31%).(3) A novel TiO2double light-scattering layer (TiO2-DLL) film electrode consisting of TiO2hollow spheres (TiO2-HS) as overlayer and TiO2nanosheets (TiO2-NS) as underlayer was designed as the photoelectrode of dye-sensitized solar cells (DSSCs). The TiO2-DLL film had increased specific surface area and enhanced light scattering capability, which were confirmed by N2adsorption-desorption measurement and UV-visible reflectance spectra measurement. Furthermore, the TiO2-NS underlayer enlarged the contact area and increased the contact points between TiO2-DLL film and conducting glass. Consequently, TiO2-DLL DSSCs achieved enhanced conversion efficiency, reaching up to5.08%.