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Title: A Silicon Ratchet to Produce Power from Below-Bandgap Photons

Abstract

Our work computationally demonstrates a new photovoltaic mechanism that generates power from incoherent, below-bandgap (THz) excitations of conduction band electrons in silicon. A periodic sawtooth potential, realized through elastic strain gradients along a 100 nm thick Si slab, biases the oscillatory motion of excited electrons, which preferentially jump and relax into the adjacent period on the right to generate a net current. The magnitude of the ratchet current increases with photon energy (20, 50, and 100 meV) and irradiance (≈MW cm –2), which control the probability of photon scattering, and peaks as a function of the well depth of the ratchet potential, and the dominant mode of energy loss (the 62 meV intervalley phonon). The internal power conversion efficiency of the ratchet has a maximum of 0.0083% at a photon energy of 100 meV, due to inefficiencies caused by isotropic scattering. This new photovoltaic mechanism uses wasted below-bandgap absorptions to enhance the directional diffusion of charge carriers and could be utilized to augment the efficiency of traditional photovoltaics.

Authors:
 [1];  [1];  [1];  [1]; ORCiD logo [1]
  1. Northwestern Univ., Evanston, IL (United States)
Publication Date:
Research Org.:
Northwestern Univ., Evanston, IL (United States). Energy Frontier Research Center (EFRC) Center for Bio-Inspired Energy Science (CBES)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1469980
Alternate Identifier(s):
OSTI ID: 1375821
Grant/Contract Number:  
SC0000989
Resource Type:
Accepted Manuscript
Journal Name:
Advanced Energy Materials
Additional Journal Information:
Journal Volume: 7; Journal Issue: 22; Related Information: CBES partners with Northwestern University (lead); Harvard University; New York University; Pennsylvania State University; University of Michigan; University of Pittsburgh; Journal ID: ISSN 1614-6832
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; below‐bandgap; infrared; photovoltaics; ratchet; silicon

Citation Formats

Lau, Bryan, Kedem, Ofer, Kodaimati, Mohamad, Ratner, Mark A., and Weiss, Emily A. A Silicon Ratchet to Produce Power from Below-Bandgap Photons. United States: N. p., 2017. Web. doi:10.1002/aenm.201701000.
Lau, Bryan, Kedem, Ofer, Kodaimati, Mohamad, Ratner, Mark A., & Weiss, Emily A. A Silicon Ratchet to Produce Power from Below-Bandgap Photons. United States. doi:10.1002/aenm.201701000.
Lau, Bryan, Kedem, Ofer, Kodaimati, Mohamad, Ratner, Mark A., and Weiss, Emily A. Tue . "A Silicon Ratchet to Produce Power from Below-Bandgap Photons". United States. doi:10.1002/aenm.201701000. https://www.osti.gov/servlets/purl/1469980.
@article{osti_1469980,
title = {A Silicon Ratchet to Produce Power from Below-Bandgap Photons},
author = {Lau, Bryan and Kedem, Ofer and Kodaimati, Mohamad and Ratner, Mark A. and Weiss, Emily A.},
abstractNote = {Our work computationally demonstrates a new photovoltaic mechanism that generates power from incoherent, below-bandgap (THz) excitations of conduction band electrons in silicon. A periodic sawtooth potential, realized through elastic strain gradients along a 100 nm thick Si slab, biases the oscillatory motion of excited electrons, which preferentially jump and relax into the adjacent period on the right to generate a net current. The magnitude of the ratchet current increases with photon energy (20, 50, and 100 meV) and irradiance (≈MW cm–2), which control the probability of photon scattering, and peaks as a function of the well depth of the ratchet potential, and the dominant mode of energy loss (the 62 meV intervalley phonon). The internal power conversion efficiency of the ratchet has a maximum of 0.0083% at a photon energy of 100 meV, due to inefficiencies caused by isotropic scattering. This new photovoltaic mechanism uses wasted below-bandgap absorptions to enhance the directional diffusion of charge carriers and could be utilized to augment the efficiency of traditional photovoltaics.},
doi = {10.1002/aenm.201701000},
journal = {Advanced Energy Materials},
number = 22,
volume = 7,
place = {United States},
year = {2017},
month = {8}
}

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