Glancing-angle Deposited Titanium Dioxide Films And Its Modification For Dye-sensitized Solar Cells

Porous TiO₂films with both4μm thickness and helical columnar structure weresuccessfully prepared by the electron-beam evaporation system by glancing-angledeposition method. Such porous films had a large specific surface area that couldabsorb more dye and caused the light-to-electricity efficiency to reach3.34%³.38%.Considering the pores among the columnar crystals were still very big with averagesize of0.5μm, so three methods of dip coating, spin coating and electrophoresis wereperformed to treat the as-deposit films. The purpose was further to improve thespecific surface area of the film, to increase the dye-absorption quantity and finally toimprove the light-to-electricity efficiency.Film structure is analyzed by X-ray diffraction meter; the surface and cross-sectionmorphologies by scanning electron microscope; the dye-desorption quantities byUV-Visible photometer and the DSSC properties by solar simulator I-V measurementsystem.It’s found that the spiral columnar structure not only made the film crystallize wellat low temperature （350oC） but also absorb more dye. In addition, one-dimensionalstructure caused the electrons transfer easily and the efficiency is up to3.34%³.38%.After the treatment of dip coating, the film roughness rise and the dye-absorptionquantities increased obviously, which made efficiencies improved by9%¹2%. Therewere no obvious differences with film crystallinity and morphology after treated byspin coating. It’s thought that TiO₂nano-crystal rotated into the pores crystallized withthe columns which increased the roughness and surface area. The efficiency of thefilm treated by spin coating was elevated to15%. When the electrophoresis time was5min,15min or25min, the morphologies of the film treated by electrophoresislooked the same as the one treated by spin coating because the electrophoresisquantities of TiO₂nano-particles were not very high, and the efficiency was improvedby11%,7.8%and9.3%, respectively. As the electrophoresis time extending, it can bewatched the TiO₂particles apparently while the crystallinity descended at he sametime. It’s analyzed that on the condition of not affecting the film crystallinity, ifincreasing the dye-absorption quantities, the efficiency would be improvedeffectively.