Resonant Transport in Single Diketopyrrolopyrrole Junctions

We study the single-molecule
transport properties of small bandgap
diketopyrrolopyrrole oligomers (DPPn, n = 1–4) with lengths varying from 1 to 5 nm. At a low bias
voltage, the conductance decays exponentially as a function of length
indicative of nonresonant transport. However, at a high bias voltage,
we observe a remarkably high conductance close to 10–2 G0 with currents reaching over 0.1 μA across all
four oligomers. These unique transport properties, together with density
functional theory-based transport calculations, suggest a mechanism
of resonant transport across the highly delocalized DPP backbones
in the high bias regime. This study thus demonstrates the unique properties
of diketopyrrolopyrrole derivatives in achieving highly efficient
long-range charge transport in single-molecule devices.