Most measurements of electron transport in single-molecule devices have focused on a low-bias regime where the dominant mechanism involves off-resonant tunneling or superexchange. Here, we achieve resonant transport with a remarkably high conductance and differential conductance in a series of diketopyrrolopyrrole oligomers (DPPn), ranging in length from 1 to 5 nm. By leveraging level alignment control through a solvent gating effect, we additionally demonstrate two-channel resonant transport through the highest occupied and lowest unoccupied orbitals for the DPP dimer. This has enabled us to interrogate a single-molecule in an unprecedented excited state where both frontier orbitals are partially occupied. This unique resonant transport picture is further explored by thermopower and temperature-dependent measurements and rationalized by <i>ab-inito</i> calculations. Our demonstrations not only expose rich physics of resonant transport at the single-molecule level, but also represent a new strategy for building functional single-molecule devices using an ambipolar component.  <br/>

Resonant tunneling transport in single-molecule junctions

255th National Meeting (2018)

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