Highly efficient sensitization of titanium dioxide

Desilvestro, Jean; Gräetzel, Michael; Kavan, Ladislav; Moser, Jacques-E.; Augustyński, Jan

doi:10.1021/ja00296a035

Cited by 405 publications

(248 citation statements)

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“…[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. 32 Interestingly, this molecular analogue to the interfacial Reaction 2 is known to be catalyzed by redox active compounds and by interactions with Lewis bases.…”

Section: Recombinationmentioning

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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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%

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

et al. 2009

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“…Among these wide bandgap semiconductors, titania (TiO 2 ), an n-type semiconductor with a wide bandgap (3.2 eV for anatase), has been well known and widely used in the photoanode of DSCs. As early as 1985, Desilvestro et al (Desilvestro et al, 1985) have showed that if TiO 2 is used in a nanoparticle form, the power conversion efficiency of DSC can be drastically enhanced. The improvement of conversion efficiency lies in the superiority of nanoparticles to create large surface, which was demonstrated by a comparison between a flat film and a 10-μm-thick film that consisted of nanoparticles with an average size of 15 nm (Oregan & Gratzel, 1991).…”

Section: Semiconductor Nanoparticlesmentioning

confidence: 99%

“…1) (Oregan & Gratzel, 1991). They greatly improved the power energy conversion efficiency from lower than 2.5 to 7%, and the main reasons for the improvement were as follows: (1) the preparation of nanostructured TiO 2 film (Desilvestro et al, 1985), (2) the use of ruthenium complex that was adequately bonded to TiO 2 nanoparticles and (3) the selected organic liquid electrolyte based on iodide/triiodide. The jump in solar energy conversion efficiency has attracted considerable attentions and motivated significant optimism with respect to the feasibility of DSCs as a cost-effective alternative to conventional solar cells.…”

Section: Introductionmentioning

confidence: 99%

The Application of Inorganic Nanomaterials in Dye-Sensitized Solar Cells

Chen¹,

Tian²,

Tang³

et al. 2011

Solar Cells - Dye-Sensitized Devices

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“…Since only a monolayer of adsorbed dye molecules was photoactive, light absorption was low and limited when flat surfaces of the semiconductor electrode were employed. This inconvenience was solved by introducing polycrystalline TiO 2 (anatase) films with a surface roughness factor of several hundreds (Desilvestro et al, 1985;Vlachopoulos et al, 1988). The amount of adsorbed dye was increased even further by using mesoporous electrodes, providing a huge active surface area thereby, and cells combining such electrodes and a redox electrolyte based on iodide/triiodide couple yielded 7% conversion efficiencies in 1991 (O´Regan & Gratzel, 1991).…”

Section: Brief Description Of Dsscmentioning

confidence: 99%

Photon Management in Dye Sensitized Solar Cells

Colodrero¹,

Calvo²,

Míguez³

2010

Solar Energy

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Highly efficient sensitization of titanium dioxide

Abstract: The United States Government is authorized to reproduce and distribute reprints for governmental purposes notwithstanding any copyright notation thereon.Highly Efficient Sensitization of Titanium Dioxide * 0. 01 ton•" 2(CHj)2C-CH2 + (4)

Cited by 405 publications

References 5 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

The Application of Inorganic Nanomaterials in Dye-Sensitized Solar Cells

Photon Management in Dye Sensitized Solar Cells

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Highly efficient sensitization of titanium dioxide

Abstract: The United States Government is authorized to reproduce and distribute reprints for governmental purposes notwithstanding any copyright notation thereon.Highly Efficient Sensitization of Titanium Dioxide * 0. 01 ton•" 2(CHj)2C-CH2 + (4)

Cited by 405 publications

References 5 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

The Application of Inorganic Nanomaterials in Dye-Sensitized Solar Cells

Photon Management in Dye Sensitized Solar Cells

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Product

Resources

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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