Slow interfacial charge recombination in solid-state dye-sensitized solar cell using Al2O3-coated nanoporous TiO2 films

Zhang, Xintong; Liu, Hongwu; Taguchi, Takayuki; Meng, Qing; Sato, Osamu; Fujishima, Akira

doi:10.1016/j.solmat.2003.11.005

Cited by 106 publications

(52 citation statements)

References 23 publications

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“…This evidence strongly suggests that the concentration of trapped states and electron recombination can be significantly optimized by codoping TiO2 with 0.5 mol.% Mg and La, resulting in enhanced DSSC efficiency. This is made possible by the improved resistance to charge recombination with the electrolyte redox species[40].…”

mentioning

confidence: 99%

Enhanced efficiency of dye-sensitized solar cells based on Mg and La co-doped TiO 2 photoanodes

Ako

Rafieh

Ekaneyaka

et al. 2015

Electrochimica Acta

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confidence: 99%

Enhanced efficiency of dye-sensitized solar cells based on Mg and La co-doped TiO 2 photoanodes

Ako

Rafieh

Ekaneyaka

et al. 2015

Electrochimica Acta

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“…Oxide overlayers on TiO 2 have been shown to promote electron injection yields in DSSC applications by removing surface trap sites that confine the injected electron in the vicinity of the ionized dye and/or by providing an electronic barrier to backelectron transfer. This condition has been achieved with thin films of Al 2 O 3 [1441][1442][1443][1444][1445], SiO 2 [1445], NiO [698,1446,1447], ZrO 2 [1445] and ZnO [1448][1449][1450] on TiO 2 . Fabregat-Santiago et al [1441] found that a thin coating of Al 2 O 3 on TiO 2 increased the photocurrent yield in DSSC by decreasing the back-electron transfer rates by a factor of 3-4.…”

Section: Electronic Effectsmentioning

confidence: 99%

A surface science perspective on TiO2 photocatalysis

Henderson

2011

Surface Science Reports

1,858

1,634

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a b s t r a c tThe field of surface science provides a unique approach to understanding bulk, surface and interfacial phenomena occurring during TiO 2 photocatalysis. This review highlights, from a surface science perspective, recent literature that provides molecular-level insights into photon-initiated events occurring at TiO 2 surfaces. Seven key scientific issues are identified in the organization of this review. These are: (1) photon absorption, (2) charge transport and trapping, (3) electron transfer dynamics, (4) the adsorbed state, (5) mechanisms, (6) poisons and promoters, and (7) phase and form. This review ends with a brief examination of several chemical processes (such as water splitting) in which TiO 2 photocatalysis has made significant contributions in the literature.

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“…However, direct evidence for slow recombination kinetics between the electrons in the TiO 2 and the oxidized species in the electrolyte ͑I 3 − ͒ were not addressed. Due to the strong interest in this approach, 12,13 we decided to investigate further the origin of the efficiency improvement induced by the Al 2 O 3 coating. Our study combines the interpretation of several experimental techniques which address the charge-transfer processes between electrons in the TiO 2 and either the oxidized dye or the oxidized species ͑I 3 − ͒ in the electrolyte.…”

Section: Introductionmentioning

confidence: 99%

The origin of slow electron recombination processes in dye-sensitized solar cells with alumina barrier coatings

Fabregat‐Santiago

Garcı́a-Cañadas

Palomares

et al. 2004

Journal of Applied Physics

191

154

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We investigate the effect of a thin alumina coating of nanocrystalline TiO 2 films on recombination dynamics of dye-sensitized solar cells. Both coated and uncoated cells were measured by a combination of techniques: transient absorption spectroscopy, electrochemical impedance spectroscopy, and open-circuit voltage decay. It is found that the alumina barrier reduces the recombination of photoinjected electrons to both dye cations and the oxidized redox couple. It is proposed that this observed retardation can be attributed primarily to two effects: almost complete passivation of surface trap states in TiO 2 that are able to inject electrons to acceptor species, and slowing down by a factor of 3-4 the rate of interfacial charge transfer from conduction-band INTRODUCTIONNew concepts for photovoltaic energy conversion are increasingly focusing at the intersection between organic and inorganic materials. Such devices are based upon nanometerscale interpenetrating networks of electron and hole transporting materials 1-3 rather than employing the long diffusion length, high-purity crystals, as used in conventional silicon solar cells. Dye-sensitized solar cells (DSSCs) are so far the most efficient devices based on this concept. DSSCs base their ability to convert photon energy to electricity on fast conversion of photogenerated excitons to energetic charge carriers spatially separated in distinct nanoscale domains or phases. The energy associated with photoexcitation of the sensitizer dye is employed to inject electrons into the conduction band of nanocrystalline TiO 2 and the holes into the redox electrolyte, generally the I − / I 3 − redox couple in an organic solvent. Under illumination, the Fermi level of electrons in the TiO 2 is raised 4 relative to the chemical potential of the redox couple in the electrolyte, resulting in a large thermodynamic driving force (ca. 0.8 eV) for electron transfer from the TiO 2 to the redox couple. Slow kinetics for this charge recombination process are therefore essential to allow the charge carriers enough time to be collected into their respective contacts. 5 Recently, the concept of a "kinetic barrier" for interfacial charge recombination processes in DSSCs has been further demonstrated by the use of ultrathin ͑ഛ1 nm͒ conformal alumina ͑Al 2 O 3 ͒ layers deposited in situ onto the surface on the nanocrystalline metal oxide films, leading to a significant increase in DSSC energy conversion efficiencies, as reported by several groups. [6][7][8][9][10][11][12] Palomares et al. 11 investigated the electron recombination process at the interface between TiO 2 and the oxidized dye, and have shown slow kinetics for the electron transfer process when the TiO 2 nanocrystalline particles were coated with Al 2 O 3 . However, direct evidence for slow recombination kinetics between the electrons in the TiO 2 and the oxidized species in the electrolyte ͑I 3 − ͒ were not addressed. Due to the strong interest in this approach, 12,13 we decided to investigate further the origin of the effic...

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Slow interfacial charge recombination in solid-state dye-sensitized solar cell using Al2O3-coated nanoporous TiO2 films

Cited by 106 publications

References 23 publications

Enhanced efficiency of dye-sensitized solar cells based on Mg and La co-doped TiO 2 photoanodes

Enhanced efficiency of dye-sensitized solar cells based on Mg and La co-doped TiO 2 photoanodes

A surface science perspective on TiO2 photocatalysis

The origin of slow electron recombination processes in dye-sensitized solar cells with alumina barrier coatings

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