Ultrafast band-gap oscillations in iron pyrite
Name
Kolb-2013-Ultrafast band-gap oscillations.pdf
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1.08 MB
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Checksum (MD5)
195919d035192b673bb1f683b7a44ae8
Author(s)
Kolb, Brian
Kolpak, Alexie M.
Date Issued
December 2013
Journal
Physical Review B
Publisher
American Physical Society
Citation
Kolb, Brian, and Alexie Kolpak. “Ultrafast Band-Gap Oscillations in Iron Pyrite.” Phys. Rev. B 88, no. 23 (December 2013). © 2013 American Physical Society
Version
Final published version
Abstract
With its combination of favorable band gap, high absorption coefficient, material abundance, and low cost, iron pyrite, FeS[subscript 2], has received a great deal of attention over the past decades as a promising material for photovoltaic applications such as solar cells and photoelectrochemical cells. Devices made from pyrite, however, exhibit open circuit voltages significantly lower than predicted, and despite a recent resurgence of interest in the material, there currently exists no widely accepted explanation for this disappointing behavior. In this paper, we show that phonons, which have been largely overlooked in previous efforts, may play a significant role. Using fully self-consistent GW calculations, we demonstrate that a phonon mode related to the oscillation of the sulfur-sulfur bond distance in the pyrite structure is strongly coupled to the energy of the conduction-band minimum, leading to an ultrafast (≈100 fs) oscillation in the band gap. Depending on the coherency of the phonons, we predict that this effect can cause changes of up to ±0.3 eV relative to the accepted FeS[subscript 2] band gap at room temperature. Harnessing this effect via temperature or irradiation with infrared light could open up numerous possibilities for novel devices such as ultrafast switches and adaptive solar absorbers.
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
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DOI of Published Version
https://doi.org/10.1103/PhysRevB.88.235208
