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Charge carrier dynamics in tantalum oxide overlayered and tantalum doped hematite photoanodes

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Charge carrier dynamics in tantalum oxide overlayered and tantalum doped hematite photoanodes. / Ruoko, Tero-Petri; Hiltunen, Arto; Iivonen, Tomi; Ulkuniemi, Riina; Lahtonen, Kimmo; Ali-Löytty, Harri; Mizohata, Kenichiro; Valden, Mika; Leskelä, Markku; Tkachenko, Nikolai V.

julkaisussa: Journal of Materials Chemistry A, Vuosikerta 7, Nro 7, 01.2019, s. 3206-3215.

Tutkimustuotosvertaisarvioitu

Harvard

Ruoko, T-P, Hiltunen, A, Iivonen, T, Ulkuniemi, R, Lahtonen, K, Ali-Löytty, H, Mizohata, K, Valden, M, Leskelä, M & Tkachenko, NV 2019, 'Charge carrier dynamics in tantalum oxide overlayered and tantalum doped hematite photoanodes', Journal of Materials Chemistry A, Vuosikerta. 7, Nro 7, Sivut 3206-3215. https://doi.org/10.1039/C8TA09501A

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Author

Ruoko, Tero-Petri ; Hiltunen, Arto ; Iivonen, Tomi ; Ulkuniemi, Riina ; Lahtonen, Kimmo ; Ali-Löytty, Harri ; Mizohata, Kenichiro ; Valden, Mika ; Leskelä, Markku ; Tkachenko, Nikolai V. / Charge carrier dynamics in tantalum oxide overlayered and tantalum doped hematite photoanodes. Julkaisussa: Journal of Materials Chemistry A. 2019 ; Vuosikerta 7, Nro 7. Sivut 3206-3215.

Bibtex - Lataa

@article{35850f3089d24128bb223a9f88e24636,
title = "Charge carrier dynamics in tantalum oxide overlayered and tantalum doped hematite photoanodes",
abstract = "We employ atomic layer deposition to prepare 50 nm thick hematite photoanodes followed by passivating them with a 0.5 nm thick Ta 2 O 5 -overlayer and compare them with samples uniformly doped with the same amount of tantalum. We observe a three-fold improvement in photocurrent with the same onset voltage using Ta-overlayer hematite photoanodes, while electrochemical impedance spectroscopy under visible light irradiation shows a decreased amount of surface states under water splitting conditions. The Ta-doped samples have an even higher increase in photocurrent along with a 0.15 V cathodic shift in the onset voltage and decreased resistivity. However, the surface state capacitance for the Ta-doped sample is twice that of the reference photoanode, which implies a larger amount of surface hole accumulation. We further utilize transient absorption spectroscopy in the sub-millisecond to second timescale under operating conditions to show that electron trapping in both Ta 2 O 5 -passivated and Ta-doped samples is markedly reduced. Ultrafast transient absorption spectroscopy in the sub-picosecond to nanosecond timescale shows faster charge carrier dynamics and reduced recombination in the Ta-doped hematite photoanode resulting in the increased photoelectrochemical performance when compared with the Ta 2 O 5 -overlayer sample. Our results show that passivation does not affect the poor charge carrier dynamics intrinsic to hematite based photoanodes. The Ta-doping strategy results in more efficient electron extraction, solving the electron trapping issue and leading to increased performance over the surface passivation strategy.",
author = "Tero-Petri Ruoko and Arto Hiltunen and Tomi Iivonen and Riina Ulkuniemi and Kimmo Lahtonen and Harri Ali-L{\"o}ytty and Kenichiro Mizohata and Mika Valden and Markku Leskel{\"a} and Tkachenko, {Nikolai V.}",
note = "INT=phys,{"}Ulkuniemi, Riina{"}",
year = "2019",
month = "1",
doi = "10.1039/C8TA09501A",
language = "English",
volume = "7",
pages = "3206--3215",
journal = "Journal of Materials Chemistry A",
issn = "2050-7488",
publisher = "ROYAL SOC CHEMISTRY",
number = "7",

}

RIS (suitable for import to EndNote) - Lataa

TY - JOUR

T1 - Charge carrier dynamics in tantalum oxide overlayered and tantalum doped hematite photoanodes

AU - Ruoko, Tero-Petri

AU - Hiltunen, Arto

AU - Iivonen, Tomi

AU - Ulkuniemi, Riina

AU - Lahtonen, Kimmo

AU - Ali-Löytty, Harri

AU - Mizohata, Kenichiro

AU - Valden, Mika

AU - Leskelä, Markku

AU - Tkachenko, Nikolai V.

N1 - INT=phys,"Ulkuniemi, Riina"

PY - 2019/1

Y1 - 2019/1

N2 - We employ atomic layer deposition to prepare 50 nm thick hematite photoanodes followed by passivating them with a 0.5 nm thick Ta 2 O 5 -overlayer and compare them with samples uniformly doped with the same amount of tantalum. We observe a three-fold improvement in photocurrent with the same onset voltage using Ta-overlayer hematite photoanodes, while electrochemical impedance spectroscopy under visible light irradiation shows a decreased amount of surface states under water splitting conditions. The Ta-doped samples have an even higher increase in photocurrent along with a 0.15 V cathodic shift in the onset voltage and decreased resistivity. However, the surface state capacitance for the Ta-doped sample is twice that of the reference photoanode, which implies a larger amount of surface hole accumulation. We further utilize transient absorption spectroscopy in the sub-millisecond to second timescale under operating conditions to show that electron trapping in both Ta 2 O 5 -passivated and Ta-doped samples is markedly reduced. Ultrafast transient absorption spectroscopy in the sub-picosecond to nanosecond timescale shows faster charge carrier dynamics and reduced recombination in the Ta-doped hematite photoanode resulting in the increased photoelectrochemical performance when compared with the Ta 2 O 5 -overlayer sample. Our results show that passivation does not affect the poor charge carrier dynamics intrinsic to hematite based photoanodes. The Ta-doping strategy results in more efficient electron extraction, solving the electron trapping issue and leading to increased performance over the surface passivation strategy.

AB - We employ atomic layer deposition to prepare 50 nm thick hematite photoanodes followed by passivating them with a 0.5 nm thick Ta 2 O 5 -overlayer and compare them with samples uniformly doped with the same amount of tantalum. We observe a three-fold improvement in photocurrent with the same onset voltage using Ta-overlayer hematite photoanodes, while electrochemical impedance spectroscopy under visible light irradiation shows a decreased amount of surface states under water splitting conditions. The Ta-doped samples have an even higher increase in photocurrent along with a 0.15 V cathodic shift in the onset voltage and decreased resistivity. However, the surface state capacitance for the Ta-doped sample is twice that of the reference photoanode, which implies a larger amount of surface hole accumulation. We further utilize transient absorption spectroscopy in the sub-millisecond to second timescale under operating conditions to show that electron trapping in both Ta 2 O 5 -passivated and Ta-doped samples is markedly reduced. Ultrafast transient absorption spectroscopy in the sub-picosecond to nanosecond timescale shows faster charge carrier dynamics and reduced recombination in the Ta-doped hematite photoanode resulting in the increased photoelectrochemical performance when compared with the Ta 2 O 5 -overlayer sample. Our results show that passivation does not affect the poor charge carrier dynamics intrinsic to hematite based photoanodes. The Ta-doping strategy results in more efficient electron extraction, solving the electron trapping issue and leading to increased performance over the surface passivation strategy.

U2 - 10.1039/C8TA09501A

DO - 10.1039/C8TA09501A

M3 - Article

VL - 7

SP - 3206

EP - 3215

JO - Journal of Materials Chemistry A

JF - Journal of Materials Chemistry A

SN - 2050-7488

IS - 7

ER -