Preparation Of TiO₂Photo-anode And Its Application In Dye-sensitized Solar Cells

Titanium dioxide （TiO₂） nanomaterials have been widely applied in dye-sensitized solar cells,sensor, photocatalyst, water pollution treatment and air cleaning due to its advantages of richresources, chemical stability, non-toxic and low price. While in the field of dye-sensitized solar cells（DSSCs）, constantly improve the titanium dioxide semi-conducting material utilization efficiency ofsunlight is current research hotspot. In our work, we had improved photoelectric conversionefficiency of DSSCs by two ways, the one is though the design of TiO₂photo-anode’s structure, andthe other is by photo-anode’s physical doping modification.First, one dimensional TiO₂nanotube array films （TiO₂-NTs） were prepared by anodization.Though the I-t curve, the growth mechanism of TiO₂-NTs were studied. The impact of electrolyte,concentration, solvent and viscosity during anodization procedures on the morphology of TiO₂hasbeen studied by SEM. By this way, the appropriate experiment parameter has been found to prepareTiO₂-NTs. Based on the analysis of DTA-TGA curves of TiO₂-NTs, the appropriate calcinationtemperature was determined, which was500°C. By XRD analysis of TiO₂-NTs before and aftercalcination, it has been found that TiO₂has changed from amorphous state to anatase aftercalcination, which is fitful for its application in DSSCs.Then, the TiO₂nanoparticles/TiO₂nanotubes （TiO₂-NPs/TiO₂-NTs） composite film for photo-anode has been prepared by doctor blade method. By design the structure of DSSCs’photo-anode toimprove their photoelectric conversion efficiency. The previous experiment parameter was used toprepare TiO₂-NTs, at the same time, by different times of anodization, TiO₂-NTs with differentdiameters were obtained, and then they were used to fabricate the composite photo-anode film.Through the analysis of J-E curves, the influence of TiO₂-NTs’ diameter and its content to thephotoelectric conversion efficiency of DSSCs were studied. It turned out that by adding TiO₂-NPs ofdifferent diameters, the photoelectric conversion efficiency of DSSCs has improved4.15%to15.0%.It showed out the complementary advantages of zero-and-one dimensional structure of TiO₂. Withthe increase of nanotube’s diameter, the photoelectric conversion efficiency of DSSCs （） increasedto a maximum and then decreased. When the nanotube’s diameter was around44.5nm, the largest （3.60%） was got, which has increased by15.0%comparing to that of DSSCs which contained TiO₂-NPs only. With the increasement of the content of nanotubes, also increased to a maximum andthen decreased. When the content was4wt.%, the was4.16%, which has improved by32.9%. After that, by spin-coating method, the TiO₂nanoparticles/multi-walled carbon nanotubes（TiO₂-NPs/MWCNTs） composite photo-anode films were prepared. The aim of that is to improvethe photoelectric conversion efficiency of DSSCs by doping modification of TiO₂photo-anode films.The influence of adding modified MWCNTs and its content to of DSSCs were studied. The resultsshowed that the addition of MWCNTs improved the photoelectric conversion efficiency of DSSCsby13.4%. By adding modified MWCNTs, the increase of that reached to18.6%. With the increaseof MWCNTs’content, also showed downward trend after increase. When the content was0.5wt.%,was4.26%, which has increased by23.8%comparing to that of DSSCs which contained TiO₂-NPs only.