Improved dispersion ability of TiO 2 nanoparticles for efficient dye-sensitized solar cells

Abstract

The presence of large aggregates in TiO 2 paste as a result of the poor dispersion of the TiO 2 nanoparticles leads to a non-uniform nanostructured mesoporous TiO 2 film consisting irregular pore sizes, a bumpy film surface, and low dye adsorption density. This study describes organic molecular modifications to TiO 2 nanoparticles surfaces to improve the dispersion ability. Two kinds of organic molecules - ethylene glycol and acetylacetone - and commercially available P25-TiO 2 nanoparticles were solvothermally reacted to adsorb the organic molecules on TiO 2 nanoparticles surfaces. TEM nanostructural study indicated that the organic molecular layer covered on the TiO 2 nanoparticle surface, forming a core-shell nanostructure. The dispersibility of TiO 2 nanoparticles in the paste was improved by organic molecular modifications. Furthermore, effects of TiO 2 nanoparticles surface modification on photovoltaic performances of DSSCs were investigated. The performances of DSSCs with a single TiO 2 nanoparticle mesoporous layer were reduced due to the improved light transmission, lower light adsorption, after the organic molecular modification. A light reflective scattering layer on the top of the TiO 2 nanoparticle layer was used to prevent energy loss by light transmittance. The organic molecular modification together with the light scattering layer showed efficiency enhancements of 7% and 5% with acetylacetone and ethylene glycol modifications, respectively than the non-modified TiO 2 film with the scattering layer, by confirming the effectiveness of surface modifications.