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Electron Transfer Dynamics in Nanocrystalline Titanium Dioxide Solar Cells Sensitized with Ruthenium or Osmium Polypyridyl Complexes

Kuciauskas, Darius and Freund, Michael S. and Gray, Harry B. and Winkler, Jay R. and Lewis, Nathan S. (2001) Electron Transfer Dynamics in Nanocrystalline Titanium Dioxide Solar Cells Sensitized with Ruthenium or Osmium Polypyridyl Complexes. Journal of Physical Chemistry B, 105 (2). pp. 392-403. ISSN 1520-6106. https://resolver.caltech.edu/CaltechAUTHORS:20170315-151836987

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Abstract

The electron transfer dynamics in solar cells that utilize sensitized nanocrystalline titanium dioxide photoelectrodes and the iodide/triiodide redox couple have been studied on a nanosecond time scale. The ruthenium and osmium bipyridyl complexes Ru(H_2L‘)_2(CN)_2, Os(H_2L‘)_2(CN)_2, Ru(H_2L‘)_2(NCS)_2, and Os(H_2L‘)_2(NCS)_2, where H_2L‘ is 4,4‘-dicarboxylic acid 2,2‘-bipyridine, inject electrons into the semiconductor with a rate constant >10^8 s^(-1). The effects of excitation intensity, temperature, and applied potential on the recombination reaction were analyzed using a second-order kinetics model. The rates of charge recombination decrease with increasing driving force to the oxidized sensitizer, indicating that charge recombination occurs in the Marcus inverted region. The electronic coupling factors between the oxidized sensitizer and the injected electrons in TiO_2 and the reorganization energies for the recombination reaction vary significantly for the different metal complexes. The charge recombination rates are well described by semiclassical electron transfer theory with reorganization energies of 0.55−1.18 eV. Solar cells sensitized with Ru(H_2L‘)_2(CN)_2, Os(H_2L‘)_2(CN)_2, and Ru(H_2L‘)_2(NCS)_2 have favorable photoelectrochemical characteristics, and iodide is oxidized efficiently. In contrast, iodide oxidation limits the efficiency of cells based on sensitization of TiO_2 with Os(H_2L‘)_2(NCS)_2. The observation that charge recombination occurs in the Marcus inverted region has important implications for the design of molecular sensitizers in nanocrystalline solar cells operated under our experimental conditions.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/jp002545lDOIArticle
http://pubs.acs.org/doi/abs/10.1021/jp002545lPublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/jp002545lPublisherSupporting Information
ORCID:
AuthorORCID
Kuciauskas, Darius0000-0001-8091-5718
Freund, Michael S.0000-0003-1104-2292
Gray, Harry B.0000-0002-7937-7876
Winkler, Jay R.0000-0002-4453-9716
Lewis, Nathan S.0000-0001-5245-0538
Additional Information:© 2001 American Chemical Society. Received: July 18, 2000; In Final Form: September 20, 2000. Publication Date (Web): December 19, 2000. We acknowledge Dr. George Coia of Caltech for useful discussions. This work was supported by the Department of Energy, Office of Basic Energy Sciences (D.K., M.S.F., N.S.L.), and by the NSF (H.B.G., J.R.W.). We also acknowledge a generous gift in support of work on TiO2 photoelectrochemistry to Caltech by the DuPont Company.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)UNSPECIFIED
NSFUNSPECIFIED
DuPont CompanyUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20170315-151836987
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170315-151836987
Official Citation:Electron Transfer Dynamics in Nanocrystalline Titanium Dioxide Solar Cells Sensitized with Ruthenium or Osmium Polypyridyl Complexes Darius Kuciauskas, Michael S. Freund, Harry B. Gray, Jay R. Winkler, and Nathan S. Lewis The Journal of Physical Chemistry B 2001 105 (2), 392-403 DOI: 10.1021/jp002545l
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:75156
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:16 Mar 2017 16:58
Last Modified:22 Nov 2019 09:58

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