TY - JOUR
T1 - Unraveling the carrier dynamics of BiVO4
T2 - A femtosecond to microsecond transient absorption study
AU - Ravensbergen, Janneke
AU - Abdi, Fatwa F.
AU - Van Santen, Judith H.
AU - Frese, Raoul N.
AU - Dam, Bernard
AU - Van De Krol, Roel
AU - Kennis, John T. M.
N1 - Publication details (e.g. title, author(s), publication statuses and dates) are captured on an “AS IS” and “AS AVAILABLE” basis at the time of record harvesting from the data source. Suggestions for further amendments or supplementary information can be sent to [email protected].
PY - 2014/12/4
Y1 - 2014/12/4
N2 - Bismuth vanadate (BiVO4) is a promising semiconductor material for photoelectrochemical water splitting showing good visible light absorption and a high photochemical stability. To improve the performance of BiVO4, it is of key importance to understand its photophysics upon light absorption. Here we study the carrier dynamics of BiVO4 prepared by the spray pyrolysis method using broadband transient absorption spectroscopy (TAS), in thin films as well as in a photoelectrochemical (PEC) cell under water-splitting conditions. The use of a dual-laser setup consisting of electronically synchronized Ti:sapphire amplifiers enable us to measure the femtosecond to microsecond time scales in a single experiment. On the basis of this data, we propose a model of carrier dynamics that includes relaxation and trapping rates for electrons and holes. Hole trapping occurs in multiple phases, with the majority of the photogenerated holes being trapped with a time constant of 5 ps and a small fraction of this hole trapping taking place within the instrument response of 120 fs. The induced absorption band that represents the trapped holes is modulated by an oscillation of 63 cm-1, which is assigned to the coupling of holes to a phonon mode. We find electrons to undergo a relaxation with a time constant of 40 ps, followed by deeper trapping on the 2.5 ns time scale. On time scales longer than 10 ns, trap-limited recombination that follows a power law is found, spanning time scales up to microseconds. Finally, we observe no spectral or kinetic differences by applying a bias voltage to the PEC cell, indicating that the effect of a voltage and the charge transfer processes between BiVO4 and the electrolyte occurs on longer time scales. Our results therefore provide new insights into the carrier dynamics of BiVO4 and further expand the application window of TAS as an analytical tool for photoanode materials. © 2014 American Chemical Society.
AB - Bismuth vanadate (BiVO4) is a promising semiconductor material for photoelectrochemical water splitting showing good visible light absorption and a high photochemical stability. To improve the performance of BiVO4, it is of key importance to understand its photophysics upon light absorption. Here we study the carrier dynamics of BiVO4 prepared by the spray pyrolysis method using broadband transient absorption spectroscopy (TAS), in thin films as well as in a photoelectrochemical (PEC) cell under water-splitting conditions. The use of a dual-laser setup consisting of electronically synchronized Ti:sapphire amplifiers enable us to measure the femtosecond to microsecond time scales in a single experiment. On the basis of this data, we propose a model of carrier dynamics that includes relaxation and trapping rates for electrons and holes. Hole trapping occurs in multiple phases, with the majority of the photogenerated holes being trapped with a time constant of 5 ps and a small fraction of this hole trapping taking place within the instrument response of 120 fs. The induced absorption band that represents the trapped holes is modulated by an oscillation of 63 cm-1, which is assigned to the coupling of holes to a phonon mode. We find electrons to undergo a relaxation with a time constant of 40 ps, followed by deeper trapping on the 2.5 ns time scale. On time scales longer than 10 ns, trap-limited recombination that follows a power law is found, spanning time scales up to microseconds. Finally, we observe no spectral or kinetic differences by applying a bias voltage to the PEC cell, indicating that the effect of a voltage and the charge transfer processes between BiVO4 and the electrolyte occurs on longer time scales. Our results therefore provide new insights into the carrier dynamics of BiVO4 and further expand the application window of TAS as an analytical tool for photoanode materials. © 2014 American Chemical Society.
UR - http://www.scopus.com/inward/record.url?scp=84915750918&partnerID=8YFLogxK
UR - https://www.scopus.com/record/pubmetrics.uri?eid=2-s2.0-84915750918&origin=recordpage
U2 - 10.1021/jp509930s
DO - 10.1021/jp509930s
M3 - RGC 21 - Publication in refereed journal
SN - 1932-7447
VL - 118
SP - 27793
EP - 27800
JO - The Journal of Physical Chemistry C
JF - The Journal of Physical Chemistry C
IS - 48
ER -