Single-walled carbon nanotube scaffolds for dye-sensitized solar cells

The influence of single-walled carbon nanotube (SWCNT) architectures for facilitating charge transport in mesoscopic semiconductor films has been probed using a TiO2/Ru(II) trisbipyridyl complex system. Both transient absorption and emission measurements indicate that the SWCNT network in the film has no noticeable influence on the charge injection process from the excited Ru(II) trisbipyridyl complex into TiO2 particles. However, it plays an important role in improving the charge separation, as the rate of back electron transfer between the oxidized sensitizer (Ru(III)) and the injected electrons becomes slower in the presence of the SWCNT scaffold. The beneficial aspect of charge collection by SWCNT has been further explored by carrying out photoelectrochemical measurements. The dye-sensitized solar cells constructed using this SWCNT scaffold show an improvement in the photocurrent generation. However, this improvement in photocurrent generation is neutralized by a lower photovoltage as the apparent Fermi level of the TiO2 and SWCNT composite becomes more positive than that of pristine TiO2.