Carrier dynamics in α-Fe2O3 (0001) thin films and single crystals probed by femtosecond transient absorption and reflectivity

Joly, Alan G.; Williams, Joshua R.; Chambers, Scott A.; Xiong, Gang; Hess, Wayne P.; Laman, David M.

doi:10.1063/1.2177426

Cited by 185 publications

(208 citation statements)

References 23 publications

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“…Clearly, the donor density measurement from the Mott-Schottky analysis is very complex; therefore, the carrier concentrations of the films were also measured using Hall measurements. We found values between 5 9 10 17 and 5 9 10 20 cm -3 , which are within the same range for other reported photoanodes, such as hematite or bismuth vanadate materials [103][104][105]. We also reported on the electronic transport properties (carrier mobility) and spectroscopic measurements (carrier recombination).…”

Section: -9supporting

confidence: 61%

Tantalum nitride for photocatalytic water splitting: concept and applications

Nurlaela

Ziani

Takanabe

2016

Mater Renew Sustain Energy

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Along with many other solar energy conversion processes, research on photocatalytic water splitting to generate hydrogen and oxygen has experienced rapid major development over the past years. Developing an efficient visible-light-responsive photocatalyst has been one of the targets of such research efforts. In this regard, nitride materials, particularly Ta 3 N 5 , have been the subject of investigation due to their promising properties. This review focuses on the fundamental parameters involved in the photocatalytic processes targeting overall water splitting using Ta 3 N 5 as a model photocatalyst. The discussion primarily focuses on relevant parameters that are involved in photon absorption, exciton separation, carrier diffusion, carrier transport, catalytic efficiency, and mass transfer of the reactants. An overview of collaborative experimental and theoretical approaches to achieve efficient photocatalytic water splitting using Ta 3 N 5 is discussed.

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Section: -9supporting

confidence: 61%

Tantalum nitride for photocatalytic water splitting: concept and applications

Nurlaela

Ziani

Takanabe

2016

Mater Renew Sustain Energy

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“…12 Using this assignment, transient absorption (TA) spectroscopic studies have reported shortlived (<100 picoseconds) photocarriers in these materials. [13][14][15][16][17][18][19][20] In contrast to these earlier findings, more recent studies have identified a long-lived (>microseconds) absorption band at 580 nm due to photogenerated holes 21,22 in nanoporous hematite films with reported high incident-photon-to-electron-conversion-efficiency (IPCE).…”

mentioning

confidence: 55%

In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe2O3) electrodes

Huang

Lin

Xiang

et al. 2012

Energy Environ. Sci.

124

163

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The spectra and dynamics of photogenerated electrons and holes in excited hematite (a-Fe 2 O 3 ) electrodes are investigated by transient absorption (from visible to infrared and from femto-to microseconds), bias-dependent differential absorption and Stark spectroscopy. Comparison of results from these techniques enables the assignment of the spectral signatures of photogenerated electrons and holes. Under the pulse illumination conditions of transient absorption (TA) measurement, the absorbed photon to electron conversion efficiency (APCE) of the films at 1.43 V (vs. reversible hydrogen electrode, RHE) is 0.69%, significantly lower than that at AM 1.5. TA kinetics shows that under these conditions, >98% of the photogenerated electrons and holes have recombined by 6 ms. Although APCE increases with more positive bias (from 0.90 to 1.43 V vs. RHE), the kinetics of holes up to 6 ms show negligible change, suggesting that the catalytic activity of the films is determined by holes with longer lifetimes.

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“…[43] This extremely low value of radiative carrier recombination 436 www.chemsuschem.org suggests that fast nonradiative processes such as carrier trapping and phonon coupling are limiting the excited-state lifetime. [51] Indeed, the ultrafast dynamics of excited states in hematite have been studied in colloidal nanoparticles, single crystals, and even nanostructured thin films using femtosecond laser spectroscopy. [43,[51][52] In nanoparticles it was found that the excited state decay profiles were independent of the pump power and the probe wavelength, and were not affected by lattice doping.…”

Section: Photogenerated Carrier Lifetimementioning

confidence: 99%

Solar Water Splitting: Progress Using Hematite (α‐Fe₂O₃) Photoelectrodes

2011

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Photoelectrochemical (PEC) cells offer the ability to convert electromagnetic energy from our largest renewable source, the Sun, to stored chemical energy through the splitting of water into molecular oxygen and hydrogen. Hematite (α-Fe(2)O(3)) has emerged as a promising photo-electrode material due to its significant light absorption, chemical stability in aqueous environments, and ample abundance. However, its performance as a water-oxidizing photoanode has been crucially limited by poor optoelectronic properties that lead to both low light harvesting efficiencies and a large requisite overpotential for photoassisted water oxidation. Recently, the application of nanostructuring techniques and advanced interfacial engineering has afforded landmark improvements in the performance of hematite photoanodes. In this review, new insights into the basic material properties, the attractive aspects, and the challenges in using hematite for photoelectrochemical (PEC) water splitting are first examined. Next, recent progress enhancing the photocurrent by precise morphology control and reducing the overpotential with surface treatments are critically detailed and compared. The latest efforts using advanced characterization techniques, particularly electrochemical impedance spectroscopy, are finally presented. These methods help to define the obstacles that remain to be surmounted in order to fully exploit the potential of this promising material for solar energy conversion.

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Carrier dynamics in α-Fe2O3 (0001) thin films and single crystals probed by femtosecond transient absorption and reflectivity

Abstract: Articles you may be interested inTransient reflectivity as a probe of ultrafast carrier dynamics in semiconductors: A revised model for lowtemperature grown GaAs

Cited by 185 publications

References 23 publications

Tantalum nitride for photocatalytic water splitting: concept and applications

Tantalum nitride for photocatalytic water splitting: concept and applications

In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe2O3) electrodes

Solar Water Splitting: Progress Using Hematite (α‐Fe₂O₃) Photoelectrodes

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Carrier dynamics in α-Fe2O3 (0001) thin films and single crystals probed by femtosecond transient absorption and reflectivity

Abstract: Articles you may be interested inTransient reflectivity as a probe of ultrafast carrier dynamics in semiconductors: A revised model for lowtemperature grown GaAs

Cited by 185 publications

References 23 publications

Tantalum nitride for photocatalytic water splitting: concept and applications

Tantalum nitride for photocatalytic water splitting: concept and applications

In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe2O3) electrodes

Solar Water Splitting: Progress Using Hematite (α‐Fe2O3) Photoelectrodes

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Solar Water Splitting: Progress Using Hematite (α‐Fe₂O₃) Photoelectrodes