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Evaluation and optimization of mass transport of redox species in silicon microwire-array photoelectrodes

Xiang, Chengxiang and Meng, Andrew C. and Lewis, Nathan S. (2012) Evaluation and optimization of mass transport of redox species in silicon microwire-array photoelectrodes. Proceedings of the National Academy of Sciences of the United States of America, 109 (39). pp. 15622-15627. ISSN 0027-8424. PMCID PMC3465373. https://resolver.caltech.edu/CaltechAUTHORS:20121101-150325621

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Abstract

Physical integration of a Ag electrical contact internally into a metal/substrate/microstructured Si wire array/oxide/Ag/electrolyte photoelectrochemical solar cell has produced structures that display relatively low ohmic resistance losses, as well as highly efficient mass transport of redox species in the absence of forced convection. Even with front-side illumination, such wire-array based photoelectrochemical solar cells do not require a transparent conducting oxide top contact. In contact with a test electrolyte that contained 50 mM/5.0 mM of the cobaltocenium^(+/0) redox species in CH_3CN–1.0 M LiClO_4, when the counterelectrode was placed in the solution and separated from the photoelectrode, mass transport restrictions of redox species in the internal volume of the Si wire array photoelectrode produced low fill factors and limited the obtainable current densities to 17.6 mA cm^(-2) even under high illumination. In contrast, when the physically integrated internal Ag film served as the counter electrode, the redox couple species were regenerated inside the internal volume of the photoelectrode, especially in regions where depletion of the redox species due to mass transport limitations would have otherwise occurred. This behavior allowed the integrated assembly to operate as a two-terminal, stand-alone, photoelectrochemical solar cell. The current density vs. voltage behavior of the integrated photoelectrochemical solar cell produced short-circuit current densities in excess of 80 mA cm^(-2) at high light intensities, and resulted in relatively low losses due to concentration overpotentials at 1 Sun illumination. The integrated wire array-based device architecture also provides design guidance for tandem photoelectrochemical cells for solar-driven water splitting.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1073/pnas.1118338109 DOIArticle
http://www.pnas.org/content/109/39/15622PublisherArticle
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3465373/PubMed CentralArticle
ORCID:
AuthorORCID
Xiang, Chengxiang0000-0002-1698-6754
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2012 National Academy of Sciences. Edited by Thomas J. Meyer, University of North Carolina at Chapel Hill, Chapel Hill, NC, and approved July 23, 2012 (received for review December 14, 2011). Published online before print August 16, 2012. This work was supported by the U.S. Department of Energy, Grant DE-FG0203ER15483 and by the Caltech Center for Sustainable Energy Research (CCSER). One of us (A.C.M.) acknowledges support from Caltech’s Summer Undergraduate Research Fellowship program. Author contributions: C.X., A.C.M., and N.S.L. designed research; C.X. and A.C.M. performed research; C.X. and A.C.M. analyzed data; and C.X., A.C.M., and N.S.L. wrote the paper.
Group:JCAP
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-FG02-03ER15483
Caltech Center for Sustainable Energy ResearchUNSPECIFIED
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Subject Keywords:semiconductor/liquid junctions; Si microwire arrays; COMSOL Multiphysics
Issue or Number:39
PubMed Central ID:PMC3465373
Record Number:CaltechAUTHORS:20121101-150325621
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20121101-150325621
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35250
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:01 Nov 2012 23:15
Last Modified:09 Mar 2020 13:19

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