Influence of addition of larger particles into 3-nm particles of TiO 2 film on the performance of dye-sensitized solar cells

The performance of dye-sensitized solar cells (DSC) based on the TiO2 film composed of 3 nm particles and mixtures of 3 nm and 400 nm or 25 nm particles synthesized by spray pyrolysis deposition has been investigated. An energy conversion efficiency of 8.44% (under the illumination of 100 mW/cm2, AM 1.5) has been achieved with the DSC based on the nanocrystalline TiO2 film consisting of 3 nm and 25 nm particles with a ratio of 3:4 by weight. The maximum incident photo-to-current conversion efficiency (IPCE) of the cell is 0.91, which is much higher than the maximum IPCE of the photoelectrode composed of either only 3 nm or the mixture of 3 nm and 400 nm particles (with the same ratio by weight) over the visible spectrum. SEM images show the formation of clusters in the TiO2 film containing 25 nm particles. It is proposed that the clusters are responsible for the high IPCE by increasing the light harvesting efficiency through enhanced light scattering and facilitating the electron transport of the DSC