Effect of the TiO2 surface modification with 3-glycidyloxypropyltrimethoxysilane on the aggregation of cresyl violet: Application to a dye-sensitized solar cell

Abstract

Dye aggregation is a typical phenomenon occurring in dye-sensitized solar cells (DSSCs), which causes a decrease in the electron injection efficiency from the photoexcited dye to titanium dioxide (TiO2). As this results in a decrease in the photovoltaic performance, it cannot be ignored in the study of DSSCs. This paper reports a DSSC involving a TiO2 electrode chemically modified by cresyl violet (CV) covalently attached to 3-glycidyloxypropyltrimethoxysilane (GPTMS). The aim of the study is to understand the influence of silane coupling agents (SCAs) on dye aggregation. Aggregation of CV occurring on the TiO2 surface was prevented by GPTMS treatment on the TiO2 surface. This result was revealed by the decreased absorption intensity of the dimeric band observed in the total transmittance spectra. Density functional theory calculations and fluorescence decay curve measurements indicated that the CV covalently attached to GPTMS acts as a photosensitizing dye in DSSCs. As a result, the photovoltaic performance of DSSCs containing CV was enhanced by preventing its aggregation upon GPTMS treatment onto the TiO2 surface (7-fold increase: 0.0020%–0.014%). We concluded that TiO2 surfaces treated with SCAs can help to prevent dye aggregation, and therefore, enhance the photovoltaic performance of DSSCs.