Ultrafast carrier dynamics in BiVO4 thin film photoanode material

interplay between free carriers, trapped carriers and low-frequency lattice vibrations

K. T. Butler, B. J. Dringoli, L. Zhou, P. M. Rao, A. Walsh, L. V. Titova

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

We explore ultrafast carrier dynamics and interactions of photoexcited carriers with lattice vibrational modes in BiVO4 photoanode material using time-resolved terahertz spectroscopy and first-principles phonon spectrum calculations. We find that photoexcited holes form bound polaron states by introducing lattice distortion that changes phonon spectrum and suppresses the Ag phonon mode associated with opposite motion of Bi and VO4 molecular units. At excitation fluence higher than 1 mJ cm2 (or 2 × 1015 cm2 per pulse), lattice distortion due to self-localized holes alters the lattice symmetry and vibrational spectrum, resulting in bleaching of THz absorption by Ag phonons. Concurrently, we observe a short lived population of free carriers which exhibit Drude conductivity with mobility on the order of 200 cm2 V1 s1, orders of magnitude higher than typical carrier mobility in BiVO4. The anomalously high carrier mobilities are explained in the framework of a Mott transition. This demonstration of enhanced transport suggests how engineering BiVO4 photoanodes to take advantage of free carrier transport under high excitation conditions may in the future significantly enhance performance of photoelectrochemical devices.

Original languageEnglish
Pages (from-to)18516-18523
Number of pages8
JournalJournal of Materials Chemistry A
Volume4
Issue number47
DOIs
Publication statusPublished - 21 Dec 2016

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Lattice vibrations
Carrier mobility
Terahertz spectroscopy
Gene Conversion
Thin films
Carrier transport
Vibrational spectra
Phonons
Bleaching
Demonstrations

Cite this

Ultrafast carrier dynamics in BiVO4 thin film photoanode material : interplay between free carriers, trapped carriers and low-frequency lattice vibrations. / Butler, K. T.; Dringoli, B. J.; Zhou, L.; Rao, P. M.; Walsh, A.; Titova, L. V.

In: Journal of Materials Chemistry A, Vol. 4, No. 47, 21.12.2016, p. 18516-18523.

Research output: Contribution to journalArticle

Butler, K. T. ; Dringoli, B. J. ; Zhou, L. ; Rao, P. M. ; Walsh, A. ; Titova, L. V. / Ultrafast carrier dynamics in BiVO4 thin film photoanode material : interplay between free carriers, trapped carriers and low-frequency lattice vibrations. In: Journal of Materials Chemistry A. 2016 ; Vol. 4, No. 47. pp. 18516-18523.
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