The Yield and Mobility of Charge Carriers in Smooth and Nanoporous TiO<sub>2</sub> Films

Savenije, Tom J.; Haas, Matthijs P. de; Warman, J. M.

doi:10.1524/zpch.1999.212.part_2.201

Cited by 68 publications

(85 citation statements)

References 12 publications

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“…This behavior has also been reported elsewhere, [17,39,45,46] and it has been attributed to the competition between electron trap filling and higher-order recombination. At such, it has been used as a signature for the presence of trap states in semiconductors (i.e., trap-assisted recombination).…”

Section: Resultssupporting

confidence: 82%

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

Jang

Friedrich

Müller

et al. 2017

Advanced Energy Materials

119

164

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Widespread application of solar water splitting for energy conversion is largely dependent on the progress in developing not only efficient, but also cheap and scalable photoelectrodes. Metal oxides, which can be deposited with scalable techniques and are relatively cheap, are particularly interesting, but high efficiency is still hindered by the poor carrier transport properties (i.e., carrier mobility and lifetime). In this paper, a mild hydrogen treatment is introduced to bismuth vanadate (BiVO4), which is one of the most promising metal oxide photoelectrodes, as a method to overcome the carrier transport limitations. Timeresolved microwave and terahertz conductivity measurements reveal more than two-fold enhancement of the carrier lifetime for the hydrogen-treated BiVO4, without significantly affecting the carrier mobility. This is in contrast to the case of tungsten-doped BiVO4, although hydrogen is also shown to be a donor type dopant in BiVO4. The enhancement in carrier lifetime is found to be caused by significant reduction of trap-assisted recombination, either via passivation of deep trap states or reduction of trap state density, which can be related to vanadium anti-site on bismuth or vanadium interstitials according to density functional theory calculations. Overall, these findings provide further insights on the interplay between defect modulation and carrier transport in metal oxide photoelectrodes, which will benefit the development of low-cost, highly-efficient solar energy conversion devices.

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Section: Resultssupporting

confidence: 82%

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

Jang

Friedrich

Müller

et al. 2017

Advanced Energy Materials

119

164

View full text Add to dashboard Cite

show abstract

“…The photoinduced change in the conductance of the sample on flash photolysis, ⌬G, was monitored as a change in the microwave power, ⌬P / P, reflected by the cavity at resonance ͑ϳ9 GHz͒ using microwave circuitry and detection equipment, which has been described elsewhere. [20][21][22][23] The two parameters are related by…”

Section: Methodsmentioning

confidence: 99%

“…[20][21][22][23] This is free of electrodes and operates at low electric fields ͑ഛ100 V / cm͒. Because of the high frequency of the electric field ͑9 GHz͒, charge carriers are not required to cross grain or domain boundaries, in contrast to dc conductivity measurements.…”

Section: Introductionmentioning

confidence: 99%

Electrodeless time-resolved microwave conductivity study of charge-carrier photogeneration in regioregular poly(3-hexylthiophene) thin films

et al. 2004

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The electrodeless flash-photolysis time-resolved microwave conductivity technique (FP-TRMC) has been used to study the photogeneration of charge carriers in spin-coated films of regioregular poly(3-hexylthiophene) ͑P3HT͒, over the photon energy range from 1.9 to 5.2 eV for incident light intensities from 10 13 to 10 16 photons/ cm 2 per ͑3 ns͒ pulse. The initial, single-photon quantum yield of photoionization, , has been estimated from the low-intensity limit to the photoconductivity based on a charge carrier mobility of 0.014 cm 2 /Vs (determined in separate pulse-radiolysis TRMC experiments on bulk P3HT). The value of is constant at ͑1.7± 0.4͒% within the range 1.9-3.0 eV, which encompasses the first electronic absorption band of P3HT. Above 3.0 eV, increases, up to a value of ͑7±2͒% at 5.2 eV. The activation energy of the photoconductivity was found to be approximately 50 meV at all photon energies. The high-intensity, sublinear dependence of the photoconductivity can be described by the occurrence of either exciton-exciton annihilation or diffusional charge recombination with rate coefficients of 2.3ϫ 10 −8 cm 3 / s and 1.1ϫ 10 −8 cm 3 /s.

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“…9 GHz͒ using microwave circuitry and detection equipment, which has been described elsewhere. [11][12][13][14] The two parameters are related by…”

Section: Methodsmentioning

confidence: 99%

“…The aforementioned problems can be circumvented using the flash-photolysis time-resolved microwave conductivity ͑FP-TRMC͒ technique, [11][12][13][14] which operates at low electricfields ͑ഛ100 V cm −1 ͒. Charge carriers are detected by the absorption of microwaves and no electrodes or dc fields are required.…”

Section: Introductionmentioning

confidence: 99%

Signature of exciton annihilation in the photoconductance of regioregular poly(3-hexylthiophene)

2005

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The transient photoconductance in drop-cast films of regioregular poly͑3-hexylthiophene͒ has been studied over the photon energy range from 1.7 to 2.8 eV for incident light intensities from 10 13 to 10 16 photons/ cm 2 per 4 ns pulse. Charge carriers were detected using an electrodeless, time-resolved microwave conductivity technique. The photon-energy dependence of the photoconductance for a 15 m thick, optically dense film was found to be very different from that of a submicrometer thick film, which could not be explained by the differences in light absorption alone. A model based on exciton-exciton annihilation, however, with a rate coefficient of ͑0.9± 0.8͒ ϫ 10 −8 cm 3 / s, can reproduce the spectra as a function of film thickness and incident intensity. From kinetic fits of the conductance transients, bimolecular charge recombination can be excluded as the main origin of the nonlinear dependence of the photoconductance on the light intensity. The quantum yield of photoionization, , was found to be constant at ͑2.5± 0.4͒% within the investigated photon energy range.

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The Yield and Mobility of Charge Carriers in Smooth and Nanoporous TiO₂ Films

Cited by 68 publications

References 12 publications

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

Electrodeless time-resolved microwave conductivity study of charge-carrier photogeneration in regioregular poly(3-hexylthiophene) thin films

Signature of exciton annihilation in the photoconductance of regioregular poly(3-hexylthiophene)

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The Yield and Mobility of Charge Carriers in Smooth and Nanoporous TiO2 Films

Cited by 68 publications

References 12 publications

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

Enhancing Charge Carrier Lifetime in Metal Oxide Photoelectrodes through Mild Hydrogen Treatment

Electrodeless time-resolved microwave conductivity study of charge-carrier photogeneration in regioregular poly(3-hexylthiophene) thin films

Signature of exciton annihilation in the photoconductance of regioregular poly(3-hexylthiophene)

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The Yield and Mobility of Charge Carriers in Smooth and Nanoporous TiO₂ Films