Self-assembled Microspheres From TiO₂ Nanorods And Its Application In Quantum Dots Sensitized Solar Cells

At present,Energy crisis and environmental problems has so become two major issues urgent to be solved.Solar cells are the basic device which transforming solar energy into electricity by photovoltaic effects.The development of solar cell technology plays an important role in solving energy and environmental problems.Quantum dots sensitized solar cells?QDSSCs?have lower cost,higher theoretical efficiency,great research value and good prospects for development.In fact,the actual photoelectric conversion efficiency of QDSSCs is much lower than that of dye-sensitized solar cells,the main influencing factors are the structure of wide bandgap semiconductor photoanode films,the utilization of solar spectroscopy by quantum dot sensitizers,the charge recombination of photoanode and electrolyte interface.In this paper,we mainly study the effect of QDSSCs photoanode films on the cell efficiency.TiO₂ nanorods,which combined the advantages of TiO₂ nanocrystalline and one-dimensional TiO₂ nanowires,have a large specific surface area which is in favour of adsorbing enough quantum dot sensitizers,and provide fast transmission channels for electrons to reduce the composite probability and increase the current density.In this paper,TiO₂ nanorods with a length of 20-30 nm and a diameter of about 3 nm were synthesized by hydrothermal method,and photoanode films with different concentrations of TiO₂ nanorods was applied to solar cells by Cd S/Cd Se co-sensitization.We investigated the effect of nanorod's concentrations on photoelectric conversion efficiency of the cells,and finally we got a highest photoelectric conversion efficiency which reached 3.19%.The addition of polar solvent to TiO₂ nanorod dispersion resulted in the self-assembly submicron spheres from TiO₂ nanorods.The surface and interior of the microspheres were composed of a large number of TiO₂ nanorods,and the surface of microspheres was rough in the nanometer scale range,though the surface of microspheres was dense.Submicron structure of TiO₂ nanorod microspheres can increase the capacity of light scattering and improve the absorption and utilization of quantum dots.By adjusting the rate of addition of polar solvents and the concentration of dispersions,we obtained the TiO₂ nanorod microspheres with good balling property and photovoltaic,and we applied it in QDSSCs resulting in a high photoelectric conversion efficiency of 4.07%.The photoanode with the mixture configuration of TiO₂ nanorod microspheres and TiO₂ nanocrystalline colloid in QDSSCs can increase the capacity of light scattering and enhance the light absorption and utilization of quantum dots.The high specific surface area makes TiO₂ nanocrystalline colloid adsorbing enough quantum dots,while improving the connectivity between the microspheres and the electron transport efficiency of photoanode.We optimized the structure of photoanode by adjusting the ratio of the two materials,and finally got a high photoelectric conversion efficiency of 4.58%.