Inverse rectification in donor-acceptor molecular heterojunctions.
The transport properties of a junction consisting of small donor-acceptor molecules bound to Au electrodes are studied and understood in terms of its hybrid donor-acceptor-electrode interfaces. A newly synthesized donor-acceptor molecule consisting of a bithiophene donor and a naphthalenediimide acceptor separated by a conjugated phenylacetylene bridge and a nonconjugated end group shows rectification in the reverse polarization, behavior opposite to that observed in mesoscopic p-n junctions. Solution-based spectroscopic measurements demonstrate that the molecule retains many of its original constituent properties, suggesting a weak hybridization between the wave functions of the donor and acceptor moieties, even in the presence of a conjugated bridge. Differential conductance measurements for biases as high as 1.5 V are reported and indicate a large asymmetry in the orbital contributions to transport arising from disproportionate electronic coupling at anode-donor and acceptor-cathode interfaces. A semi-empirical single Lorentzian coherent transport model, developed from experimental data and density functional theory based calculations, is found to explain the inverse rectification.
Department of Mechanical Engineering, University of California, 201D Gilman Hall, Berkeley, California 94720-1462, USA.
Shannon K
SK
Yee
Jibin
J
Sun
Pierre
P
Darancet
T Don
TD
Tilley
Arun
A
Majumdar
Jeffrey B
JB
Neaton
Rachel A
RA
Segalman
D000114:Acetylene / Q000031:analogs & derivatives* / Q000737:chemistry; D004563:Electrochemistry; D004566:Electrodes; D006046:Gold / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D009281:Naphthalenes / Q000737:chemistry*; D013876:Thiophenes / Q000737:chemistry*
D009281:Naphthalenes; D013876:Thiophenes; C031721:naphthalene; C044736:phenylacetylene; D006046:Gold; D000114:Acetylene