Preparation And Photoelectrochemical Properties Of Photoanodes For Dye-sensitized Solar Cells

Dye-sensitized solar cell(DSSC) has attracted more and more attentions nowadays. Great efforts have been made to improve the performance on DSSC. However, TiO2is the semiconductor with wide band gap of approximate3.2eV, which means it can only absorb3-5%of UV light among the solar spectrum. On the other hand, the charge transfer speed in TiO2is relatively lower and the possibility of photo-generated charge and holes recombination is higher, resulting in lower utilization of solar energy. Novel photoanode materials have attracted researchers home and abroad.In this paper, we modified TiO2photoanodes to improve its photoelectrochemical performance. Carbon-incorporated TiO2microspheres were composited with pure P25to raise the charge transfer to improve the photoelectric properties of DSSC. In addition, materials such as LiTi5O12and Ta2O5were investigated, aiming to substitute TiO2in photoanode. The main results are as follows:Microspherical carbon-incorporated TiO2powders were prepared by flame assisted thermolysis and applied for fabricating dye sensitized solar cells with screen printing method. The structure, surface morphology of resulted TiO2powders were studied by X-ray diffraction, scanning electron microscopy, and X-ray energy dispersive spectroscopy, respectively. Dye sensitized solar cells were prepared by a composite from P25and the as-prepared TiO2microspheres and enhanced performance was observed for the dye-sensitized solar cell with the presence of suitable amount of carbon-incorporated TiO2microspheres in photoanodes. The shot-circuit current density is4.15mA cm-2, open-circuit voltage is0.79V, fill factor is0.47, and power conversion efficiency is1.55%with10%TiO2microspheres in photoanode. It is1.47times greater than that of commercial TiO2nanoparticles (P25)-based one (1.05%). The enhanced efficiency may be resulted from its faster charge transfer and lower photo-generated hole-electron recombination with the presence of TiO2microspheres in photoelectrodes. thin film and LTO-SP composite film were fabricated using spin-coating method. Then the photoelectrochemical properties were investigated. With the increase of the carbon black, the enhanced photocurrent of composite film was observed, which means the charge transfer speed increased. Then the LTO-SP composite film was utilized in DSSC. The photovoltaic property is relatively low with short circuit current of0.0088mA cm-2.Microspherical Ta2O5powders were prepared by flame assisted thermolysis with different tantalum ethoxide/ethanol volume ratio of1:5,1:10and1:15. The obtained powders show microspherical morphology with average diameter in the range of0.5～1.0μm. Dye-sensitized solar cell photoanodes were fabricated with obtained microspheres with screen printing method. Among the three photoanodes, Ta2O5(1:10) photoanode presents the best photovoltaic performance with shot-circuit current density of0.032mA cm-2, open-circuit voltage of0.51V, fill factor of0.34, and power conversion efficiency of0.0057%. Improved photocatalytic performance is also demonstrated for Ta2O5microsphere on the degradation of methylene blue compared with commercial Ta2O5. The work provides a novel and energy saving way to synthesize microspherical Ta2O5powders which could be applied in dye-sensitized solar cells and photodegradation.