Study On Preparation And Properties Of BaSnO₃ Based Dye-sensitized Solar Cells

Due to global warming and a depleting natural gas supply, there is a need to find alternative energy sources. Solar electricity is a steadily growing energy technology today and solar cells have found markets in variety of applications ranging from consumer electronics and small scale distributed power systems to centralized megawatt scale power plants. Solar energy conversion is dominated by expensive solid-state photovoltaic cells. As low-cost cells continue to develop, the dye sensitized solar cell (Dye-Sensitized Solar Cell, DSSC) has generated considerable interest as an efficient alternative. Although already moderately efficient, this cell offers numerous areas for improvement, both electronically and optically.Since Professor M. Gr?tzel in EPFL introduced the nanoporous films into dye-derived wideband semiconductor research and made the breakthrough in the photoelectric conversion efficiency of dye-sensitized solar cells, academic and commercial interests have been paid on DSSCs for their high efficiency, their potential low-cost and simple assemble technology, especially in the past 6 years since Gr?tzel and his group team at EPFL were able to demonstrate the first 10% efficient cells certified by NREL in USA. Dye-sensitized solar cell is composed of nanocrystalline semiconductor oxide film electrode, dye sensitizers, electrolytes, counter electrode and transparent conducting substrate. Typically, dye-derived nanocrystalline titania films were used as photoanode, platinized counter electrode, filled with electrolyte solution of I3?/I? in organic solvent, then the sandwiched solar cells are formed. Due to low-cost price, abundance in the market, nontoxicity, and biocompatiblity, and as it is also used widely in health care products as well as in paints, TiO2 becomes the best choice in semiconductor till now. But, some semiconductors have been applied to built new structures and avoid the oxidation of dye. Previous research has been limited to simple binary oxides, including TiO2, ZnO, SnO2, Nb2O5 and In2O3. In contrast, the application of multication oxides has been rarely explored. To our best knowledge, the only reported ternary oxides are SrTiO3 and s Zn2SnO4. In comparison with simple binary oxides, multication oxides have more freedom to tune the materials'chemical and physical properties by altering the compositions.Different preparation methods including coprecipitation, hydrothermal and solid state reaction are employed to synthesize BaSnO3 particles to optimize the photoelectric activities of electrode materials. The photoelectric properties of BaSnO3 particles and the performances of DSSCs are investigated by surface photovoltage spectroscopy and current–voltage measurements. The light-to-electricity conversion of 1.1% is preliminarily reached on the DSSC made of the coprecipitation-derived BaSnO3 particles.1. Different preparation methods including coprecipitation, hydrothermal and solid state reaction are employed to synthesize BaSnO3 particles to optimize the photoelectric activities of electrode materials. Which have a size distribution in the range of 0.3-1.1μm. The cell of coprecipitation-derived BaSnO3 particles exhibits the best photovoltaic performance, which is attributed to sufficient dye adsorption and good electronic interaction between BaSnO3 and dye. The results suggest that the controlling synthesis process would be a key strategy to apply appropriate material for dye-sensitized solar cells.2. The BaSnO3 film was obtained by scraping method. BaSnO3 slurry was prepared by grinding the mixture of BaSnO3 powder water, dispersant acetylacetone and Triton X-100. Then the slurry was scraped on the conductive glass plate. The BaSnO3 film was heated at 550 oC for 30 min to remove some impurities and produce nanoporous. BaSnO3 /dye electrode was fabricated by immersing the nanoporous BaSnO3 film into dye N719 solution(5×10-5 M)for 24 h. The cell was assembled by dropping an electrolyte solution into the space between the BaSnO3 /dye electrode and the counter eletrode. Then the performance test was carried on electrochemical workstation CHI660. The light-to-electricity conversion of 1.1% is preliminarily reached on the DSSC made of the coprecipitation-derived BaSnO3 particles.3. BaSnO3 grains with the shapes of rhombic dodecahedron have been synthesized via a facile modified hydrothermal approach. The crystallization behavior and the morphology evolution of the sample during heating treatment have been studied with the X-ray diffraction, scanning electron microscopy, Raman scattering and Fourier transform infrared spectroscopy. The sample with the single-phase of BaSnO3 can be obtained at the hydrothermal temperature of 240 oC, and the grain size of the product grows with increasing temperature from 10μm to 15μm before 270 oC. But, the grain size was decreased sharply to 4μm when the temperatures at 280 oC. The ultraviolet-visible absorption spectroscopy and surface photovoltage spectroscopy analysis indicated that controlling the size and shape of perovskite oxides is of great importance in photophysical properties of BaSnO3 powder.