Study On TiO₂ Dye-Sensitized Solar Cells And Photoelectric Properties Of BaSnO₃ Nanoparticles

The solar energy is a inexhaustible green energy. It is one of the optimal way to resolve energy crisis. Dye-Sensitized Solar Cell (DSSC) is a new type of the solar cell. Because of its simple fabrication procidure, low cost, better stability and clean energy, DSSC has arouse world researches and application prospect. In this paper, the making process of the DSSCs was shown, the relations between the photoelectric properties and the semiconductor electrode, Pt coated electrode, the components of the eletrolyte were studied, and a DSSC with solar energy conversion efficiency of 2.26% was abtained. The surface photovoltaic properties of the BaSnO₃ nanoparticles and the (Bu4N)2(Ru)(dcbpyH)2(NCS)2 (called N719) sensitized BaSnO₃ were investigated. N719 is a efficient sensitizer for BaSnO₃ nanoparticles. The transfer of charge carriers between the dye and the semiconductor accounts for the photosensitization phenomenon. The results are useful for the application of N719-BaSnO₃ in DSSCs. 1. The TiO₂ film was obtained by scraping method. TiO₂ slurry was prepared by grinding the mixture of TiO₂ powder (P25), water, dispersant acetylacetone and Triton X-100. Then the slurry was scraped on the conductive glass plate. The TiO₂ film was heated at 550 oC for 30 min to remove some impurities and produce nanoporous. TiO₂/dye electrode was fabricated by immersing the nanoporous TiO₂ film into dye N719 solution(5×10-5 M)for 24 h. The Pt coated FTO as counter eletrode was prepared by thermal decomposition method. The cell was assembled by dropping an electrolyte solution into the space between the TiO₂/dye electrode and the counter eletrode. Then the performance test was carried on electrochemical workstation CHI660.2. The influence such as the heat treating temperature, keeping time in the dye solution, TiCl4 treatment of the TiO₂ film, the composition of the electrolyte, the Pt coated counter electrode on the solar cell performance were investiged. The results show that there are better photoelectric properties under the condition of heat treatment at 550 oC for 30 min, TiCl4 treating for 30min, immersed in the N719 solution (5×10-5 M) for 24 h of the TiO₂ film. In addition, the additive 4-tert-butylpyridine in the eletrolyte and the Pt coated on the counter eletrode could increase the solar energy conversion efficiency of the DSSC. Under the irradiation of 100 mW/cm2 by simulated solar light, the solar energy conversion efficiency of a DSSC with 0.25 cm2 was 2.26%. And the short circuit current, the open circurt voltage and the fill factor was 614 mV, 1.62 mA, and 0.57 respectively.3. Dye-sensitized Solar Cell is a kind of novel solar cell, it keeps a close and profound relationship with photosynthesis of plants. In this paper, DSSC and photosynthesis are analyzed and compared in terms of principle, structure and constituent materials respectively. It is concluded that DSSC is the simulation of photosynthetic units. To some extent, DSSC is attributed to the inspiration which comes from natural phenomena.The significance of recognizing the relation between them is also discussed as follows:(1) It is uesful to understand the working mechanism of the DSSC.(2) Learning from the nature, the structure of the DSSC could be improved.(3) It is enlightened to extract and synthesis natrual dyes.(4) The constituent materials in the photosynthesis could be applied to the DSSC.4. BaSnO₃ nanoparticles were prepared by the sol-gel method. The surface photovoltaic properties of the samples were investigated by surface photovoltage spectroscopy and electric field induced surface photovoltage spectroscopy. It can be found that the BaSnO₃ nanoparticles exhibit an obvious surface photovoltaic response in the wavelength range of 300-450 nm with a maximum at 357 nm. The surface photovoltaic properties of the N719-BaSnO₃ nanocomposites were also studied. The results indicate that N719 can enhance the photovoltaic response as well as extend the photovoltaic response range of BaSnO₃ nanoparticles to the visible region. The transfer of charge carriers between the dye and the semiconductor accounts for this photosensitization phenomenon. Valence band spectra prove that the relative energy levels of N719 and the as-prepared BaSnO₃ nanoparticles fit well with the energy requirements for efficient electron injection. These results show that the N719-sensitized BaSnO₃ nanocomposites have potential applications in future photovoltaic devices especially in DSSCs. BaSnO₃ is an important ceramic material widely studied on its dielectric and photocatalytic properties. Its photovoltaic properties, however, have scarcely been reported. In this work,Surface photovoltaic properties of the BaSnO₃ nanoparticles and N719-BaSnO₃ composites were investigated by surface photovoltage spectroscopy and electric field induced surface photovoltage spectroscopy. Thses results not only reveal more comprehensive investigation of BaSnO₃ nanoparticles, but also the semiconductor materials in DSSCs are enriched, new materials with better quality may be found.