Ultrathin Exfoliated TiO2 Nanosheets Modified with ZrO2 for Dye-Sensitized Solar Cells

作者：Luan Xinning; Wang Ying^*

来源：Journal of Physical Chemistry C, 2014, 118(33): 18917-18923.

DOI：10.1021/jp5052112

In the present work, we use chemical exfoliation to fabricate ultrathin two-dimensional anatase TiO2 nanosheets (NSs) for application as photoanode materials in dye-sensitized solar cells. For the first time, colloidal Ti0.91O2 NSs are synthesized via chemical exfoliation of a layered precursor (HxTi2-x/4 square O-x/4(4)center dot H2O; square: vacancy, x = 0.7) through ion exchange with tetrabutylammonium (TBA(+)) cations. The as-prepared Ti0.91O2 NSs are well-dispersed and ultrathin with a lateral size of up to a few micrometers. Subsequent acid treatment induces colloidal Ti0.91O2 to reassemble and precipitate into a gelation form, followed by thermal annealing to convert the Ti0.91O2 gelation into anatase TiO2 nanosheets for applications as photoanode materials in DSSCs. Because of the enhanced light absorption and dye absorption resulting from the high surface area of ultrathin TiO2 nanosheets, the DSSC consisting of 8.8 mu m thick TiO2 nanosheet film delivers the highest energy conversion efficiency of 4.76% and the largest short-circuit current of 9.30 mA cm(-2), among DSSCs based on TiO2 nanosheet films of various thicknesses. It is noted that an overly thick TiO2 NS film will not further increase DSSC efficiency because the thicker layer results in a longer pathway for electron transport and more electron hole recombination. Moreover, a ZrO2 ALD coating combined with TiCl4 treatment on TiO2 NS film can effectively enhance the efficiency of DSSCs to 7.33% by significantly creating more surface area for more dye loading and preventing electron hole recombination between TiO2 and the dye/electrolyte, respectively.

• 出版日期2014-8-21