Thermodynamic Control over the Competitive Anchoring of N719 Dye on Nanocrystalline TiO₂ for Improving Photoinduced Electron Generation

Abstract

TiO(2) electrodes, sensitized with the N719 dye at high immersion temperatures during the sensitization process, were found to have large fractions of weakly bound N719 on the electrode surface, which resulted in dye aggregation and decreased device longevity. These disadvantages were ameliorated using a low-temperature stearic acid (SA)-assisted anchoring method described here. The activation energy (ΔE(NS)(++)) and relative fraction of strongly bound N719 were twice as large as the respective values obtained without the use of SA. Slowing of adsorption, both by thermal means and through SA-mediated processes, effectively controlled the binding mode of N719 on the surface of TiO(2). The resulting sensitized electrodes displayed enhanced device longevity and improved generation of photoinduced electrons.

Doubly open-ended TiO2nanotube arrays decorated with a few nm-sized TiO2nanoparticles for highly efficient dye-sensitized solar cells

“…We rst optimized the length of the NTs and investigated the effects of the thickness on the photovoltaic performances of DSCs prepared using NT layers with a variety of thicknesses (11-27 mm). The electrodes were sensitized with the dye molecules by immersion in a 0.3 M ethanolic solution of (Bu 4 N) 2 Ru(dcbpyH) 2 (NCS) 2 (N719 dye) for 24 h. 23 The TiO 2 electrode and semi-transparent Pt-coated FTO (uorinated tinoxide) counter electrode were sandwiched together using 60 mm thick hot-melt Surlyn spacers. A liquid electrolyte solution composed of 0.03 M I 2 , 0.6 M 1-butyl-3-methylimidazolium iodide (BMII), 0.1 M guanidinium thiocyanate, 0.5 M LiI and 0.5 M 4-tert-butylpyridine in acetonitrile and valeronitrile (85 : 15) was introduced between the sensitized and counter electrodes using a syringe.…”

Dye molecules in electrolytes: new approach for suppression of dye-desorption in dye-sensitized solar cells

“…Faster dye-adsorption has also been studied under high temperature8, high concentration9 and electric field10 in order to reduce the time for the dye-adsorption process, which resulted in improved productivity. In addition to the view point of kinetics for dye-adsorption, the viewpoint of thermodynamics was considered to control the binding mode of the dye with a co-adsorbent to obtain improved photoelectron generation11.…”

Enhanced performance of dye-sensitized solar cells with dual-function coadsorbent: reducing the surface concentration of dye–iodine complexes concomitant with attenuated charge recombination

“…1). 32 Therefore, the decrease of dye loading in this study suggested that the competitive equilibrium anchoring process may disfavor the formation of dye aggregates on the surfaces of the nanocrystalline TiO 2 electrode. Oleic acid at a concentration of 0.3 mM yielded absorption intensities of 71%; this value dramatically decreased as the concentration of coadsorbent was increased by a factor of 10 (to 3.0 mM).…”