Fabrication of dye sensitized solar cells with improved multi-layer photonodes of hydrothermally grown TiO2 nanocrystals in different autoclaving pHs

Abstract

In this research dye sensitized solar cells (DSCs) with multilayer photopanodes made of small and large TiO2 nanocrystals were fabricated. These nanocrystals were hydrothermally grown in two different basic autoclaving pHs of 10.0 and 12.0. The dominant sizes of TiO2 NCs were measured about 15 and 70 nm for the growth in the mentioned pHs, respectively. The layers composed of 15 nm TiO2 nanocrystals were well-transparent with high amount of dye adsorption. That is while the layers made of 70 nm TiO2 nanoparticles demonstrated a high level of light scattering and lower amount of dye adsorption. Different multilayer photoanodes including one, two and three sub-layers of 15 nm TiO2 nanocrystals and one over-layer of 70 nm TiO2 nanoparticles were fabricated. Then the influence of the semi-scattering over-layer of the photanodes on the performance of corresponding DSCs was investigated. The results demonstrated that a maximum efficiency of 7.7% was achieved for a cell with a multilayer photoanode made of three sub-layers of small TiO2 nanocrystals and one over-layer of 70 nm TiO2 nanoparticles. This efficiency was increased about 16% compared to that of the cell with simple three layer photoanode. The reason was mainly attributed to the increased dye loading amount of the photoanodes with one semi-light scattering over-layer.