LAUSR

Abstract In this research sub-micron size carbon spheres were hydrothermally grown with sizes around 500–550 nm. TiO 2 nanocrystals (NCs) were also prepared through a hydrothermal approach with dominant size of 20 nm. The TiO 2 NCs and carbon spheres were applied to make carbon-TiO 2 pastes with different weight percents of the included carbon spheres. The different pastes were deposited on FTO glass substrates and annealed to remove the carbon spheres from the layers. As a result some nanocrystalline TiO 2 layers with included sub-micron and micron size cavities were fabricated. The density of cavities was higher and their corresponding size was larger for the layers formed of the carbon-TiO 2 pastes with higher included carbon spheres. CdS nanocrystals were grown on the surface of these different TiO 2 layers of various porosities as the light sensitizers. Finally these TiO 2 layers with included large cavities were applied as the photoelectrode of the quantum dot sensitized solar cells (QDSCs). The effect of density/size of the cavities on the light scattering level of the photoelectrodes and the photovoltaic performance of corresponding QDSCs was investigated. The results demonstrated that the maximum energy conversion efficiency was belonged to the QDSC with a photoelectrode made of carbon-TiO 2 paste with 8 wt% of the included carbon spheres. This efficiency was about 2.75% which was increased about 87% compared to that of the reference cell with cavity-free photoelectrode.