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Published Online February 15, 2007
Science DOI: 10.1126/science.1137149

Reports

Submitted on November 3, 2006
Accepted on January 29, 2007

Thermoelectricity in Molecular Junctions

Pramod Reddy 1, Sung-Yeon Jang 2, Rachel Segalman 3*, Arun Majumdar 4*

1 Applied Science and Technology Program, University of California Berkeley, CA 94720, USA.
2 Department of Chemical Engineering, University of California, Berkeley, CA 94720, USA; Materials Science Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA; Present address: Optoelectronic Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea.
3 Applied Science and Technology Program, University of California Berkeley, CA 94720, USA; Department of Chemical Engineering, University of California, Berkeley, CA 94720, USA; Materials Science Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA.
4 Applied Science and Technology Program, University of California Berkeley, CA 94720, USA; Materials Science Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720, USA; Departments of Mechanical Engineering and Materials Science and Engineering, University of California, Berkeley, CA 94720, USA.

* To whom correspondence should be addressed.
Rachel Segalman , E-mail: segalman{at}berkeley.edu
Arun Majumdar , E-mail: majumdar{at}me.berkeley.edu

By trapping molecules between two gold electrodes with a temperature difference across them, the junction Seebeck coefficient of 1,4-benzenedithiol (BDT), 4,4'-dibenzenedithiol (DBDT) and 4,4''-tribenzenedithiol (TBDT) in contact with gold was measured at room temperature to be (+8.7 ± 2.1) microvolts per Kelvin (µV/K), (+12.9 ± 2.2) µV/K, and (+14.2 ± 3.2) µV/K, respectively. The positive sign unambiguously indicates p-type (hole) conduction in these heterojunctions, while the Au Fermi level position for Au-BDT-Au junctions was identified to be 1.2 eV above the highest occupied molecular orbital (HOMO) level of BDT. The ability to study thermoelectricity in molecular junctions provides the opportunity to address these fundamental unanswered questions about their electronic structure while also offering an opportunity to begin exploring molecular thermoelectric energy conversion.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Nuclear Coupling and Polarization in Molecular Transport Junctions: Beyond Tunneling to Function.
M. Galperin, M. A. Ratner, A. Nitzan, and A. Troisi (2008)
Science 319, 1056-1060
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