Dye-Sensitized SnO<sub>2</sub> Electrodes with Iodide and Pseudohalide Redox Mediators

Bergeron, Bryan V.; Márton, András; Oskam, Gerko; Meyer, Gerald J.

doi:10.1021/jp0461347

Cited by 128 publications

(83 citation statements)

References 40 publications

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“…26,27 The second explanation is that the TiO 2 (e -)s are good one electron reductants, perhaps best thought of as Ti(III) trap states, that are unable to facilitate the 2e -reduction of I 3 -, which is in fact the only reaction observed for I 3 -at metallic electrodes. [28][29][30] In addition, quinone/hydroquinone redox mediators that achieved some success in the older dye sensitized literature also involve two-electron transfer. 31 Significantly, it has been known for some time that the reaction of aqueous Ti(III) ions with I 3 -is also kinetically sluggish with an activation energy of 80 kcal/ mol, Reaction 3.…”

Section: Recombinationmentioning

confidence: 99%

“…[75][76][77][78] It has previously been shown that the reduced ruthenium compound studied here, Ru(bpz -)(bpz)(deeb) + does not efficiently transfer electrons to TiO 2 and that the yield can be improved by utilizing SnO 2 which has a more favorable conduction band energy. 28 For application in photogalvanic cells or other energy conversion assemblies, the low cage escape yield (0.042) for excited state hole transfer will certainly be detrimental. Some of the factors that control cage escape yields have previously been elucidated for molecular excited states.…”

Section: A Imentioning

confidence: 99%

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Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I⁻ Oxidation and I₃⁻ Photodissociation

et al. 2009

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Direct 355 or 532 nm light excitation of TBAI 3 , where TBA is tetrabutyl ammonium, in CH 3 CN at room temperature yields an iodine atom, I • , and an iodine radical anion, I 2 -• . In the presence of excess iodide, the iodine atom reacts quantitatively to yield a second equivalent of I 2 -• with a rate constant of k ) 2.5 ( 0.4 × 10 10 M -1 s -1 . The I 2 -• intermediates are unstable with respect to disproportionation and yield initial reactants, k ) 3.3 ( 0.1 × 10 9 M -1 s -1 . The coordination compound Ru(bpz) 2 (deeb)(PF 6 ) 2 , where bpz is 2,2′-bipyrazine and deeb is 4,4′-(C 2 H 5 CO 2 ) 2 -2,2′-bipyridine, was prepared and characterized for mechanistic studies of iodide photo-oxidation in acetonitrile at room temperature. Ru(bpz) 2 (deeb) 2+ displayed a broad metal-to-ligand charge transfer (MLCT) absorption band at 450 nm with ε ) 1.7 × 10 4 M -1 cm -1 . Visible light excitation resulted in photoluminescence with a corrected maximum at 620 nm, a quantum yield φ ) 0.14, and an excited state lifetime τ ) 1.75 µs from which k r ) 8.36 × 10 4 s -1 and k nr ) 5.01 × 10 5 s -1 were abstracted. Arrhenius analysis of the temperature dependent excited state lifetime revealed an activation energy of ∼2500 cm -1 and a pre-exponential factor of 10 10 s -1 , assigned to activated surface crossing to a ligand field or MLCT excited state. Steady state light excitation of Ru(bpz) 2 (deeb) 2+ in a 20 mM TBAI acetonitrile solution resulted in ligand loss photochemistry with a quantum yield of 5 × 10 -5 . The MLCT excited state was dynamically quenched by iodide with K sv ) 1.1 × 10 5 M -1 and k q ) 6.6 ( 0.3 × 10 10 M -1 s -1 , a value consistent with diffusion-limited electron transfer. Excited state hole transfer to iodide was quantitative but the product yield was low due to poor cage escape yields, φ CE ) 0.042 ( 0.001. Nanosecond transient absorption was used to quantify the appearance of two photoproducts [Ru(bpz -)(bpz)(deeb)] + and I 2 -• . The coincidence of the rate constants for [Ru(bpz -)(bpz)(deeb)] + formation and for excited state decay indicated reductive quenching by iodide. The rate constant for the appearance of I 2 -• was about a factor of 3 slower than excited state decay, k ) 2.4 ( 0.2 × 10 10 M -1 s -1 , indicating that I 2 -• was not a primary photoproduct of excited state electron transfer. A mechanism was proposed where an iodine atom was the primary photoproduct that subsequently reacted with iodide, I • + I -f I 2 -• . Charge recombination Ru(bpz -)(bpz)(deeb) + + I 2 -• f Ru(bpz) 2 (deeb) 2+ + 2I -was highly favored, ∆G o ) -1.64 eV, and well described by a second-order equal concentration kinetic model, k cr ) 2.1 ( 0.3 × 10 10 M -1 s -1 .

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Section: Recombinationmentioning

confidence: 99%

Section: A Imentioning

confidence: 99%

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I⁻ Oxidation and I₃⁻ Photodissociation

et al. 2009

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“…The corrosiveness of the I -/I 3 --based electrolytes is thus a strong driving force in the quests for the alternative redox couples. Two main directions can be identified nowadays, one toward molecular species (such as ferrocene-, hydroquinone-based redox couples [87], LiBr/Br 2 [88], Br [90,91], stable organic radicals originating from 2,2,6,6-tetramethyl-1-piperidinyloxy or N,N 0 -di-m-tolyl-N,N 0 -diphenylbenzidine compound [92], and sulfur-containing species [93]) and another direction aiming at transitionmetal-based systems (like Co(II)/(III) [94], Cu(I)/(II) [95], Ni(III)/Ni(IV) [96]). One of the most promising alternative redox couple is non-corrosive sulfurcontaining redox couple for which the conversion efficiency up to 6.4% were measured at standard test conditions [93].…”

Section: Electrolytementioning

confidence: 99%

Dye-Sensitized Solar Cells

Hočevar

Berginc

Krašovec

et al. 2012

Sol-Gel Processing for Conventional and Alternative Energy

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Dye-sensitized solar cells (DSSCs) are recognized as one of the world's leading innovation in nanosciences and photovoltaic technology. In contrast to the conventional silicon-based solar cells the demand on purity of materials for DSSC is lower and forecasted manufacturing costs are approximately halved which make the DSSCs attractive alternative. Nowadays the conversion efficiency of DSSCs exceeds 10% which makes it competitive with other thin film solar cells. In this chapter the structure and the fundamental operation of the DSSC are presented. Afterwards the properties and requirements for each individual component used in a DSSC are given. In addition advanced hybrid DSSC systems also are presented. In overall, the emphasis of this chapter is given to the involvement of sol-gel chemistry in the preparation of the individual DSSCs components, primarily of TiO 2 layers and electrolytes.

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“…Expecting that redox couple, Wang et al [69] used Br − /Br 2 as redox couple in eosin sensitized solar cells. SCN − /(SCN) 2 couple, SeCN − /(SeCN) 2 couple were also shown in the literature [70,71]. Sapp [72] reported the substituted bipyridyl cobalt(III/II) couple as redox couple in DSC.…”

Section: Electrolytementioning

confidence: 55%

Review of Recent Progress in Dye-Sensitized Solar Cells

Kong

Dai

Wang

2007

Advances in OptoElectronics

141

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We introduced the structure and the principle of dye-sensitized solar cell (DSC). The latest results about the critical technology and the industrialization research on dye-sensitized solar cells were reviewed. The development of key components, including nanoporous semiconductor films, dye sensitizers, redox electrolyte, counter electrode, and conducting substrate in dye-sensitized solar cells was reviewed in detail. The developing progress and prospect of dye-sensitized solar cells from small cells in the laboratory to industrialization large-scale production were reviewed. At last, the future development of DSC was prospective for the tendency of dye-sensitized solar cells.

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Dye-Sensitized SnO₂ Electrodes with Iodide and Pseudohalide Redox Mediators

Cited by 128 publications

References 40 publications

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I⁻ Oxidation and I₃⁻ Photodissociation

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I⁻ Oxidation and I₃⁻ Photodissociation

Dye-Sensitized Solar Cells

Review of Recent Progress in Dye-Sensitized Solar Cells

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Dye-Sensitized SnO2 Electrodes with Iodide and Pseudohalide Redox Mediators

Cited by 128 publications

References 40 publications

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I− Oxidation and I3− Photodissociation

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I− Oxidation and I3− Photodissociation

Dye-Sensitized Solar Cells

Review of Recent Progress in Dye-Sensitized Solar Cells

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Dye-Sensitized SnO₂ Electrodes with Iodide and Pseudohalide Redox Mediators

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I⁻ Oxidation and I₃⁻ Photodissociation

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I⁻ Oxidation and I₃⁻ Photodissociation