| As non-crystal semiconductor solar cells, photoelectrochemical (PEC) solar cells, led by dye-sensitized solar cells (DSSC), enjoy the advantages of low cost of raw material, simple production process, low threshold of market access, short energy recycling cycle et al. In recent years, DSSC has become one of the hottest research areas in the research field of materials, physics and chemistry related to environment and energy. Although the DSSC has made a photoelectric conversion efficiency of higher than12%, the preparation technology for highly efficient DSSC is only in the hands of a few research groups. Moreover, the preparation for highly efficient DSSC needs highly pure dye. The purification yield of dye is not high, which increases the cost of DSSC. Therefore, the methods to enhance the efficiency of ordinary DSSC and prepare low cost DSSC are of great importance for research. Since TiO2is the electrode material of the most efficient DSSC, the effective control over the microstructure of TiO2, such as grain size, crystal phase, defects/vacancies and exposed facets, is of great significance for the improvement of DSSC’s performance.In this paper, based on the photoelectrodes of DSSCs, aiming to prepare highly efficient and stable PEC solar cells, research has been done on preparing TiO2nanoparticles and nanosheets, surface modification and developing a new material with high stability. The main contents include:1. TiO2nanopaticle was synthesized by a sol-hydrothermal method, using titanium isopropoxide as the precursor. The effect of synthesis condition on grain size, crystallinity and phase transformation between phase-pure rutile and phase-pure anatase, was researched. It was revealed that the crystal-type, crystallinity and crystal-size (from10-20nm nanopaticles to120nm nanorods) of TiO2nanoparticles could be controlled by the controlling of the pre-thermal treatment, hydrothermal temperature and concentration of the precursor. A paste, made from the nanoparticles and terpinol, and a doctor-blade technology which could control the thickness of the film were utilized to make a DSSC, which could achieve a photoelectric conversion efficiency of8.65%, as a result of the phase-pure anatase, appropriate grain size and favorable crystallinity of the TiO2nanoparticles.2. Facilitated by TiO2particles absorbing La3+in hydrosol, La-doped TiO2was prepared by a sol-hydrothermal method. It was showed that the obtained La-doped anatase TiO2surface provided a higher density of oxygen vacancies without a change in the BET surface area. A theoretical calculation was carried out to explain the generation mechanism of the increased oxygen vacancies. The results showed that the La-doped anatase TiO2(101) surface tends to engender oxygen vacancies. The photoelectric conversion efficiency of dye-sensitized solar cells fabricated from1mol%La-doped TiO2reached6.72%, which gave an efficiency improved by13.5%compared with that of the cells fabricated from pure TiO2. The improvement in the efficiency was ascribed to more dye adsorbed on the surface of TiO2.3. UV irradiation was utilized to remove the fluorine-surfactant on the surface of anatase TiO2nanosheets with a high percentage of exposed{001} facets which were synthesized with the aid of hydrofluoric acid. The nanosheets treated with UV irradiation for40min had the advantage of improving the photoelectric conversion efficiency of DSSCs by17.6%, comparing to that without UV treatment when they were introduced into DSSCs as photoanode materials. The improved efficiency was ascribed to more dye adsorption. A theoretical calculation was proposed that UV irradiation induced microfaceted steps on the TiO2surface by two domain (1×4) reconstruction after UV irradiating the (1×1)(001) surface. The microfaceted steps increase the active surface area of the TiO2nanosheets by increasing the exposure of titanium atoms and engendering active sites.4. In the development of new materials, BiVO4PEC solar cells, a kind of PEC solar cell without dye and I-/I3-was developed. BiVO photoeletrode acts as the function of light absorbing material and electron conducting material. It is equivalent to a dye-coated TiO2photoelectrode. The BiVO4PEC solar cell’s efficiency is more than14times higher than the highest efficiency reported in the literature for similar cell efficiency. Compared with the Fe2O3PEC solar cell, a suggestion was proposed to develop new materials:those materials with a long lifetime of photo-generated carrier are suitable for the PEC solar cell. An electrode for photocatalytic water splitting, performing high photocatalytic activity at a low bias, is suitable for a PEC solar cell.This research, which focuses on the control over the microstructure of TiO2, such as particle size, crystal phase, defects/vacancies and exposed facets, and the exploration of BiVCO4material, is aiming at providing experimental basis and theoretical guidance on developing highly efficient and stable PEC solar cells. |
PDF Full Text Request