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.
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.
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
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
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
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
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