Self-Assembly of 3-Aminopropyltrimethoxysilane to Improve the Efficiency of Dye-Sensitized Solar Cells

Abstract

A dye-sensitized solar cell (DSSC) based on a 3-aminopropyltrimethoxysilane (APTS)-modified TiO2 electrode was fabricated. This cell generated a short current of 18.32 mA•cm^(-2), an open voltage of 775.9 mV, and its overall photo-to-electricity conversion efficiency was 9.15% under 100 mW•cm^(-2) white light irradiation from a xenon lamp. The three DSSC parameters for the bare TiO2 electrode were found to be 18.08 mA•cm^(-2), 749.9 mV, and 7.70%. Compared with the unmodified solar cell, the overall conversion efficiency improved by 18.8% and the fill factor improved from 0.57 to 0.64. This improvement is attributed to the inhibition of the back reaction at the interface between the semiconductor and the electrolyte. The dark current-applied voltage curve shows that the onset voltage shifts from -0.30 to -0.40 V, which indicates a reduction in defects and surface states on the TiO2 surface because of the presence of APTS. Furthermore, special experiments were conducted to investigate the interaction among TiO2, APTS, and the cis-Ru(dcpyH2)2(SCN)2 dye. In these experiments, APTS and the dye were self-assembled onto a TiO2 electrode in layers. The interaction was characterized by X-ray photoelectron spectroscopy (XPS). Qualitative and quantitative results showed that the -OCH2CH3 was partially removed and it formed mono-bridge or bi-bridge Si-O-Ti bonds. The cis-Ru(dcpyH2)2(SCN)2 dye adsorbed onto APTS through an electrostatic interaction between -COOH and -NH2 from the dye. FT-IR spectra further confirmed this inner interaction.