The layer boundary effect on multi-layer mesoporous TiO2 film based dye sensitized solar cells

Abstract

Multi-layer mesoporous TiO₂ prepared by screen printing is widely used for fabrication of high-efficiency dye-sensitized solar cells (DSSCs). We compare the three types of ∼10 μm thick mesoporous TiO₂ films, which were screen printed as 1-, 2- and 4-layers using the same TiO₂ nanocrystal paste. The layer boundary of the multi-layer mesoporous TiO₂ films was observed in the cross-section SEM. The existence of a layer boundary could reduce the photoelectron diffusion length with the increase of layer number. However, the photoelectron diffusion lengths of the Z907 dye sensitized solar cells based on these different layered mesoporous TiO₂ films are all longer than the film thickness. Consequently, the photovoltaic performance seems to have little dependence on the layer number of the multi-layer TiO₂ based DSSCs.