High-Performance TiO2 Photoanode with an Efficient Electron Transport Network for Dye-Sensitized Solar Cells

A titanium organic sol was synthesized for the modification of conventional porous TiO2 photoanodes for dye-sensitized solar cells (DSSCs). As a result, a compact thin TiO2 film was superimposed on the porous TiO2 structure as an efficient electron transport network, covering bare conducting substrate surface (FTO) and bridging gaps between TiO2 nanoparticles, which was confirmed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Dark current measurement suggested that the sol modified photoanode had a remarkably slower recombination rate of the photoelectrons due to the reduced bare FTO surface in comparison with the porous photoanode. The network facilitates the electron transfer in the DSSC process by removing the dead ends of electron pathways, connecting gaps along the electron pathways, and physically enlarging electron pathways, which can be demonstrated by the performance improvement of photocurrent and open-circuit potential. Consequently, the overall energy conversion efficiency of the DSSC was significantly enhanced by 28% after this simple and low-cost organic sol modification. The significant performance improvements observed from the organic sol modified DSSCs suggest that the proposed modification method is a promising alternative to the traditional TiCl4 modification method.