Photo-cathode Type Solar Cells With Rare-earth Doped Mesoporous Nano-TiO₂

For the recent decades, new energy has been attracting extensive attention fromscientists worldwide, especially the solar energy for its environment-friendliness andbeing inexhaustible, the most common form of which, DSSC （dye-sensitized solarcell） could offer superior performance in converting light energy into electricity. Uptill now, the photo-current conversion efficiencies of DSSC are comparable with thetraditional amorphous silicon solar cells but at a much lower cost and more simpleproduction processes. Therefore, the dye-sensitized solar cells have great potential fora large-scale application in the future.TiO₂has always been seen as a promising photo-catalyst for its being non-toxic,low in price and abundant in reserves, and therefore has many applications in thefields of environment-protection, water treatment and degradation of organicsubstances. However, there is also a critical problem of it that limits its furtherdevelopments–the relatively wide band gap and the subsequent low quantum yield.According to literatures, if we could properly take measures to broaden the absorptionspectrum of TiO₂, it would be possible to prepare a solar cell with high efficiencyeven without the sensitization of dyes–a photo-cathode type solar cell.In this thesis, we modified the semiconductor TiO₂material by doping with threerare earth elements: Eu, Ho and Tb. We expect that by doping with these rare earthelements, on the one hand, the micro structure of TiO₂could be optimized, and on theother hand, the absorption spectrum of the solar cell could be broadened owing to themultiple energy levels of rare earth elements. In addition, the assembly processes ofthe DSSC are investigated in this paper. Details of our research are as follows:（1） We prepared three kinds of TiO₂electrode material respectively doping the rareearth elements Eu, Ho and Tb: Eu-TiO₂, Ho-TiO₂and Tb-TiO₂by the sol-gel method.HRTEM, XRD, XPS, Raman and N2absorption-desorption are used to characterizethe material. Results show that we have successfully prepared the rare earth elementsdoped TiO₂electrode with the ratio of1:10. All the crystal forms of the TiO₂are Rutile. Particle size of the samples are between8to20nm, the BET surface area ofthe Eu-TiO₂, Ho-TiO₂and Tb-TiO₂are respectively116，103，105cm²/g, single pointpore volume reaches0.51,0.66and0.65cm³/g separately, and the average porediameter for each is146,236and221, which illustrates that the prepared materialhas good absorption property and three-dimensionally interconnectedmeso/mesoporous structure.（2） Many details of the assembly processes of the DSSC are researched in this thesis,in which we mostly focus on solving the problem of electrolyte leakage for thoseliquid type DSCs. Results show that by pre-packaging the cell with the thermoplasticmaterial Parafilm and the Pt-electrode, then injecting the electrolyte into the cell in thevacuum dryer, making the electrolyte automatically flow into the cell owing to thepressure difference, we have obtained good effects in sealing the cell.（3） We used the above electrode to prepare both dye-sensitized solar cell andphoto-cathode type solar cell respectively. Photoelectrical performances of them aretested and evaluated by analyzing the data of Voc, Electrochemical ImpedanceSpectrum, and the Linear Sweep Voltammetry.