Modified Phthalocyanines for Efficient Near-IR Sensitization of Nanostructured TiO₂ Electrode

Abstract

A zinc phthalocyanine with tyrosine substituents (ZnPcTyr), modified for efficient far-red/near-IR performance in dye-sensitized nanostructured TiO(2) solar cells, and its reference, glycine-substituted zinc phthalocyanine (ZnPcGly), were synthesized and characterized. The compounds were studied spectroscopically, electrochemically, and photoelectrochemically. Incorporating tyrosine groups into phthalocyanine makes the dye ethanol-soluble and reduces surface aggregation as a result of steric effects. The performance of a solar cell based on ZnPcTyr is much better than that based on ZnPcGly. Addition of 3alpha,7alpha-dihydroxy-5beta-cholic acid (cheno) and 4-tert-butylpyridine (TBP) to the dye solution when preparing a dye-sensitized TiO(2) electrode diminishes significantly the surface aggregation and, therefore, improves the performance of solar cells based on these phthalocyanines. The highest monochromatic incident photo-to-current conversion efficiency (IPCE) of approximately 24% at 690 nm and an overall conversion efficiency (eta) of 0.54% were achieved for a cell based on a ZnPcTyr-sensitized TiO(2) electrode. Addition of TBP in the electrolyte decreases the IPCE and eta considerably, although it increases the open-circuit photovoltage. Time-resolved transient absorption measurements of interfacial electron-transfer kinetics in a ZnPcTyr-sensitized nanostructured TiO(2) thin film show that electron injection from the excited state of the dye into the conduction band of TiO(2) is completed in approximately 500 fs and that more than half of the injected electrons recombines with the oxidized dye molecules in approximately 300 ps. In addition to surface aggregation, the very fast electron recombination is most likely responsible for the low performance of the solar cell based on ZnPcTyr.

Enhanced visible-light-driven photocatalytic performance of mesoporous W-Ti-SBA-15 prepared through a facile hydrothermal route

“…It is generally accepted that RhB molecules are sensitive to visible light and a dye-sensitized photodegradation path, instead of photocatalytic degradation, may possibly occur [49]. To exclude this possibility, 2,4-DCP, a colorless organic pollutant, was typically chosen to confirm the visible-light-driven photocatalytic destruction ability of sample 8%WTS0.7, as shown in Fig.…”

Influence of Molecular Aggregation on Electron Transfer at the Perylene Diimide/Indium-Tin Oxide Interface

“…15 Song et al 4 showed that diarylamine chlorosilane (Ar 2 N-(CH 2 ) n -SiCl 3 , Ar = 3,4-difluorophenyl) redox-active modifiers can serve as a hole-selective interfacial layer on an ITO electrode in bulk-heterojunction OPVs; the PCE of these devices was slightly higher than that of devices in which PEDOT:PSS was utilized as the interfacial layer. 4 These and other papers [15][16][17][18][19][20][21] have demonstrated that the molecular design of a redox-active modifier, such as the type, position and length of its bridging moiety and the presence of solubilizing groups or bulky substituents, may significantly affect the charge-collection kinetics and efficiency at modified TCO surfaces, because these structural parameters dictate properties such as molecular orientation, tunneling distance, degree of aggregation, and/or interface dipole magnitude and orientation.…”

Photochemical hydrogen evolution from aqueous triethanolamine solutions sensitized by binaphthol-modified titanium(IV) oxide under visible-light irradiation

“…Several strategies and methods for modifying the optical properties of TiO 2 particles, e.g., doping of a transition metal [3,4], plasma treatments [5] and nitrogen doping [6,7], have been proposed, and photoactivity under visible-light irradiation has been proved in some limited reactions. Much interest has also been shown in surface modification of TiO 2 with transition metal complexes and/or organic dyes for construction of dye-sensitized photocatalytic systems that work under visible-light irradiation [8,9] as well as for improvement of the efficiency of dye-sensitized solar cells [10][11][12].…”