Research On Modification Of Tio₂ Electrode Of Dye Sensitized Solar Cells

Dye sensitized solar cells (DSSC) have attracted great attention as the significant progress made by Gr?tzel and co-workers in the 1990s. Though investigations into the various factors influencing the photovoltaic efficiency in this novel approach have recently been intensified, there is still many problems for the optimization of the DSSC components, i.e., the oxide semiconductor, the sensitizer, the electrolyte, large area cells and the structure of DSSC.In this paper, porous TiO₂ films co-doped with Gd and N were fabricated by sol-gel method using polystyrene(PS) as pore-forming agent. The influence of the porosity and the particle size to the photoelectric properties of TiO₂ films were investigated. The relationship between the energy band of TiO₂ and dopant of Gd/N were studied by first-principles.The results indicated that anatase TiO₂ nanoparticles were the main structural components in TiO₂ films which calcined at 500℃for 2h. And the average grain size of anatase TiO₂ was found to be about 20 nm. The porous TiO₂ films with little agglomeration and flaw were used to fabricated DSSC. The I-V test show that the photoelectric properties of TiO₂ film was the best when the thickness was about 10μm, which have a short circuit current of 0.332mA/cm², an open circuit voltage of 0.382V. This is because TiO₂ film with high porosity could absorb more dye which is beneficial to enhance the photoelectric properties of TiO₂ film, and suitable thickness of TiO₂ film is in favor of transmission and transfer of carrier, all of these could enhance the photoelectric properties of TiO₂ film electrodes.And the porous TiO₂ films fabricated by sol-gel method using PS as pore-forming agent were also composed by anatase TiO₂ nanoparticles. The influence of polystyrene microspheres (PS) mass ratio to the morphology and photoelectric property of the films were investigated. The results showed that when the PS mass ratio of 7.0%, the TiO₂ thin film electrods appeared with high porosity, uniform pore size and high photoelectric property. Under simulated solar illumination, a short circuit current of 0.4979 mA/cm², an open circuit voltage of 0.6696 V and a fill factor of 38.15% were attained, which were better than the performances of TiO₂ films without pore-forming agent. And the photoelectric properties of porous TiO₂ films co-doped with 0.5% Gd and 0.3% N was the best, which had a short circuit current of 0.713 mA/cm², an open circuit voltage of 0.649 V, whose efficient was improved about 51.47% to porous TiO₂ electrode.The ground state structures and electronic properties of anatase TiO₂ co-doped with Gd and N were calculated by using first principles method which base on plane-wave pseudopotential method. The lattice constant of the samples is in good agreement with the experimental value, and the formation of doped energy-band was main based on contribution of N and 4f-orbitals of Gd. TiO₂ co-doped with Gd and N not only have a red shift, but also enhance the light absorption in the ultraviolet region, hence the TiO₂ co-doped with Gd and N could increased the electronic propertie.