Molecular Junctions

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Nanostructure-based solar- and fuel cells, both organic and inorganic, hold promise for efficiently and cheaply converting solar energy into forms convenient for storage and transportation. A primary reason for the currently low efficiency of these devices is the absence of a quantitative picture of the fundamental nonequilibrium electronic structure underlying key processes in solar energy conversion - photon absorption and charge separation, transport, and collection at organic/metal and organic/inorganic interfaces. Single molecule junctions are model interfaces between a single organic molecule connected to macroscopic metallic electrodes, and as such provide an ideal platform for developing the fundamental understanding needed.

 

In our group, we explore the interplay between local chemistry and many-body effects and how this impacts macroscopic transport and spectroscopic properties of these systems. Potential applications include the design of more efficient molecular rectifiers and single-nanostructure photovoltaics.

 

In collaboration with Latha Venkataraman at Columbia University, we study junctions of individual amine- and pyradine-based molecules trapped between gold contacts. The Venkataraman group developed a novel setup based on a scanning-tunneling microscope to vary temperature and electrical biases while the molecules remain trapped, allowing them to simultaneously measure conductivity and thermopower.

Comparison of the experimental results to our charge transport calculations reveals an unexpectedly complex relationship between conductance and thermopower arising from chemical details of the metal-molecule contact, not the simple relation usually assumed. These findings critically advance knowledge of molecular-level charge transport, laying the groundwork for molecular-scale engineering of thermoelectric and other energy conversion materials.

Related Publications

78 Darancet Nano Letters
P. T. Darancet, J. R. Widawsky, H. J. Choi, L. Venkataraman, and J. B. Neaton, "Quantitative current-voltage characteristics in molecular junctions from first principles," Nano Lett. 12, 6250 (2012). Abstract
67 Widawsky Nano Lett 2012

J. R. Widawsky, P. Darancet, J. B. Neaton, and L. Venkataraman, "Simultaneous Determination of Conductance and Thermopower of Single Molecule Junctions," Nano Lett. 12, 354–358 (2012). Abstract

63 Yee ACS Nano 2011

S. K. Yee, J. Sun, P. Darancet, T. D. Tilley, A. Majumdar, J. B. Neaton, and R. A. Segalman, "Inverse Rectification in Donor–Acceptor Molecular Heterojunctions," ACS Nano 5, 9256–9263 (2011). Abstract

58 Fatemi Nano Lett 2011

V. Fatemi, M. Kamenetska, J. B. Neaton, and L. Venkataraman, "Environmental Control of Single-Molecule Junction Transport," Nano Lett. ASAP 11, 1988–1992 (2011). Abstract

52 Quek ACS Nano 2011

S. Y. Quek, H. J. Choi, S. G. Louie, and J. B. Neaton, "Thermopower of Amine-Gold Linked Aromatic Molecular Junctions from First Principles," ACS Nano 5, 551 (2011). Abstract

M. Dell´Angela, G. Kladnik, A. Cossaro, A. Verdini, M. Kamenetska, I. Tamblyn, S. Y. Quek, J. B. Neaton, D. Cvetko, A. Morgante and L. Venkataraman, "Relating Energy Level Alignment and Amine-Linked Single Molecule Junction Conductance," Nano Lett. 10, 2470, (2010). Abstract

49 Kamenetska JACS 2010

M. Kamenetska, S. Y. Quek, A. C. Whalley, M. L. Steigerwald, H. J. Choi, S. G. Louie, C. Nuckolls, M. S. Hybertsen, J. B. Neaton, and L. Venkataraman, "Conductance and Geometry of Pyridine-Linked Single-Molecule Junctions," J. Am. Chem. Soc. 132, 6817, (2010). Abstract

M. Kotiuga, P. Darancet, C. R. Arroyo, L. Venkataraman, and J. B. Neaton, "Adsorption-Induced Solvent-Based Electrostatic Gating of Charge Transport through Molecular Junctions," Nano Lett. 15, 4498 (2015). Abstract

B. Capozzi, J. Xia, O. Adak, E. J. Dell, Z.-F. Liu, J. C. Taylor, J. B. Neaton, L. M. Campos, and L. Venkataraman, "Single-molecule diodes with high rectification ratios through environmental control," Nature Nanotechnol. 10, 522 (2015). Abstract

28 Chang ChemMat
W. B. Chang, C.-K. Mai, M. Kotiuga, J. B. Neaton, G. C. Bazan, and R. A. Segalman, "Controlling the Thermoelectric Properties of Thiophene-Derived Single-Molecule Junctions," Chem. Mater. 26, 7229 (2014). Abstract