Improved dispersion ability of TiO2 nanoparticles for efficient dye-sensitized solar cells

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The presence of large aggregates in TiO2 paste as a result of the poor dispersion of the TiO2 nanoparticles leads to a non-uniform nanostructured mesoporous TiO2 film consisting irregular pore sizes, a bumpy film surface, and low dye adsorption density. This study describes organic molecular modifications to TiO2 nanoparticles surfaces to improve the dispersion ability. Two kinds of organic molecules—ethylene glycol and acetylacetone—and commercially available P25-TiO2 nanoparticles were solvothermally reacted to adsorb the organic molecules on TiO2 nanoparticles surfaces. TEM nanostructural study indicated that the organic molecular layer covered on the TiO2 nanoparticle surface, forming a core–shell nanostructure. The dispersibility of TiO2 nanoparticles in the paste was improved by organic molecular modifications. Furthermore, effects of TiO2 nanoparticles surface modification on photovoltaic performances of DSSCs were investigated. The performances of DSSCs with a single TiO2 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 TiO2 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 TiO2 film with the scattering layer, by confirming the effectiveness of surface modifications.