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Measurement of minority-carrier diffusion lengths using wedge-shaped semiconductor photoelectrodes

Pala, Ragip A. and Leenheer, Andrew J. and Lichterman, Michael and Atwater, Harry A. and Lewis, Nathan S. (2014) Measurement of minority-carrier diffusion lengths using wedge-shaped semiconductor photoelectrodes. Energy and Environmental Science, 7 (10). pp. 3424-3430. ISSN 1754-5692. https://resolver.caltech.edu/CaltechAUTHORS:20140825-152741705

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Abstract

Measurement of the photocurrent as a function of the thickness of a light absorber has been shown herein both theoretically and experimentally to provide a method for determination of the minority-carrier diffusion length of a sample. To perform the measurement, an illuminated spot of photons with an energy well above the band gap of the material was scanned along the thickness gradient of a wedge-shaped, rear-illuminated semiconducting light absorber. Photogenerated majority carriers were collected through a back-side transparent ohmic contact, and a front-side liquid or Schottky junction collected the photogenerated minority carriers. Calculations showed that the diffusion length could be evaluated from the exponential variation in photocurrent as a function of the thickness of the sample. Good agreement was observed between experiment and theory for a solid-state silicon Schottky junction measured using this method. As an example for the application of the technique to semiconductor/liquid-junction photoelectrodes, the minority-carrier diffusion length was determined for graded thickness, sputtered tungsten trioxide and polished bismuth vanadate films under back-illumination in contact with an aqueous electrolyte. This wedge technique does not require knowledge of the spectral absorption coefficient, doping, or surface recombination velocity of the sample.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1039/C4EE01580KDOIArticle
http://pubs.rsc.org/en/Content/ArticleLanding/2014/EE/C4EE01580KPublisherArticle
http://www.rsc.org/suppdata/ee/c4/c4ee01580k/c4ee01580k1.pdfPublisherSupplementary Information
ORCID:
AuthorORCID
Lichterman, Michael0000-0002-0710-7068
Atwater, Harry A.0000-0001-9435-0201
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© Royal Society of Chemistry 2014. Received 22 May 2014, Accepted 29 July 2014. First published online 29 July 2014. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. We thank C. Garland for advice on polishing techniques. Electronic supplementary information (ESI) available: Additional equations for photocurrent calculations, XRD for WO_3 deposited at various temperature, optical determination of thickness profile, cyclic voltammetry scan of WO_3 electrodes, and further details on the ALD processing and polishing. See DOI: 10.1039/c4ee01580k
Group:JCAP
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Issue or Number:10
Record Number:CaltechAUTHORS:20140825-152741705
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20140825-152741705
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:48864
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:25 Aug 2014 22:39
Last Modified:03 Oct 2019 07:08

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