Structural change-induced negative differential resistance in polythiophene

Based on the Su–Schrieffer–Heeger model and the nonequilibrium Green’s function formalism, we have investigated charge transportation in a metal/polythiophene/metal structure. Results for the simulated conductivity include I–V curves that show an abrupt onset of negative differential resistance (NDR) with a peak-to-valley current ratio as high as 70. Combining these results with an analysis of the configuration of the molecular lattice and the reduced eigenvalues, it was found that the NDR mechanism was largely attributable to structural changes in the organic layer induced by the bias voltage. These results can help in understanding the electron–lattice coupling effect and the origin of NDR behavior in the I–V characteristics of organic molecular devices.

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► We have investigated charge transportation in a metal/polythiophene/metal structure.
► Electron–lattice coupling effects are emphasized.
► The I–V curve shows an abrupt onset of negative differential resistance (NDR).
► The peak-to-valley current ratio is as high as 70.
► The NDR was a result of conformation changes between a dimerized and a uniform state under bias.