Physical Origins of the Transient Absorption Spectra and Dynamics in Thin-Film Semiconductors

The Case of BiVO4

Jason K. Cooper, Sebastian E. Reyes-Lillo, Lucas H. Hess, Chang Ming Jiang, Jeffrey B. Neaton, Ian D. Sharp

Resultado de la investigación: Article

4 Citas (Scopus)

Resumen

Transient absorption (TA) spectroscopy is uniquely suited for understanding kinetic processes initiated by light over vast ranges of time. In combination with white light probes, the recorded differential absorption spectra can contain spectroscopic signatures characteristic of specific charge carrier population densities. However, disentangling the often-complex and convoluted spectra is made challenging without robust analysis methods relating the underlying physical mechanisms to the spectral components. In this work, we address the origin of the transient spectra of a model system of emerging solar energy harvesting materials using a monoclinic BiVO4 thin film. Using ground-state optical properties of the semiconductor, we find the main derivative-like spectral response to be related to shifting and broadening of oscillators, rather than specific carrier-related transitions. However, by using the Drude optical model of free carriers, we also identify the transient response related to free-hole density. Importantly, sample heating from the optical pumping, which begins at â10 ps and plateaus by â200 ps, dominates the overall spectral response at longer times. On the basis of a physical model of the spectral response, a kinetic model is developed that describes the pump power dependence of the free-hole density, as well as the temporal evolution of the spectral changes associated with shifting and broadening of oscillators. First-principles density functional theory calculations are used to rationalize experimental measurements. This comprehensive approach to analyzing and modeling the TA spectra offers a generalizable basis for understanding the complex pump-probe data, reveals thermal heating artifacts that are frequently erroneously assigned to long-lived photocarriers, and offers a path to eliminating ambiguity in analysis of photocarrier dynamics in solid-state systems.

Idioma originalEnglish
Páginas (desde-hasta)20642-20652
Número de páginas11
PublicaciónJournal of Physical Chemistry C
Volumen122
N.º36
DOI
EstadoPublished - 13 sep 2018

Huella dactilar

Absorption spectra
spectral sensitivity
Semiconductor materials
absorption spectra
Thin films
thin films
oscillators
Pumps
pumps
Optical pumping
Heating
Kinetics
heating
Energy harvesting
kinetics
transient response
solar energy
optical pumping
Charge carriers
Absorption spectroscopy

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Citar esto

Cooper, Jason K. ; Reyes-Lillo, Sebastian E. ; Hess, Lucas H. ; Jiang, Chang Ming ; Neaton, Jeffrey B. ; Sharp, Ian D. / Physical Origins of the Transient Absorption Spectra and Dynamics in Thin-Film Semiconductors : The Case of BiVO4. En: Journal of Physical Chemistry C. 2018 ; Vol. 122, N.º 36. pp. 20642-20652.
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abstract = "Transient absorption (TA) spectroscopy is uniquely suited for understanding kinetic processes initiated by light over vast ranges of time. In combination with white light probes, the recorded differential absorption spectra can contain spectroscopic signatures characteristic of specific charge carrier population densities. However, disentangling the often-complex and convoluted spectra is made challenging without robust analysis methods relating the underlying physical mechanisms to the spectral components. In this work, we address the origin of the transient spectra of a model system of emerging solar energy harvesting materials using a monoclinic BiVO4 thin film. Using ground-state optical properties of the semiconductor, we find the main derivative-like spectral response to be related to shifting and broadening of oscillators, rather than specific carrier-related transitions. However, by using the Drude optical model of free carriers, we also identify the transient response related to free-hole density. Importantly, sample heating from the optical pumping, which begins at {\^a}10 ps and plateaus by {\^a}200 ps, dominates the overall spectral response at longer times. On the basis of a physical model of the spectral response, a kinetic model is developed that describes the pump power dependence of the free-hole density, as well as the temporal evolution of the spectral changes associated with shifting and broadening of oscillators. First-principles density functional theory calculations are used to rationalize experimental measurements. This comprehensive approach to analyzing and modeling the TA spectra offers a generalizable basis for understanding the complex pump-probe data, reveals thermal heating artifacts that are frequently erroneously assigned to long-lived photocarriers, and offers a path to eliminating ambiguity in analysis of photocarrier dynamics in solid-state systems.",
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Physical Origins of the Transient Absorption Spectra and Dynamics in Thin-Film Semiconductors : The Case of BiVO4. / Cooper, Jason K.; Reyes-Lillo, Sebastian E.; Hess, Lucas H.; Jiang, Chang Ming; Neaton, Jeffrey B.; Sharp, Ian D.

En: Journal of Physical Chemistry C, Vol. 122, N.º 36, 13.09.2018, p. 20642-20652.

Resultado de la investigación: Article

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T1 - Physical Origins of the Transient Absorption Spectra and Dynamics in Thin-Film Semiconductors

T2 - The Case of BiVO4

AU - Cooper, Jason K.

AU - Reyes-Lillo, Sebastian E.

AU - Hess, Lucas H.

AU - Jiang, Chang Ming

AU - Neaton, Jeffrey B.

AU - Sharp, Ian D.

PY - 2018/9/13

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