Franck‐Condon Blockade and Aggregation Modulated Conductance in Molecular Devices Using Aggregation‐Induced Emission Active Molecules

We report an effective modulation of the quantum transport in molecular junctions consisting aggregation‐induced emission (AIE) active molecules. Theoretical simulations based on combined density functional theory and rate‐equation method calculations show that the low‐bias conductance of the junction with a single tetraphenylethene (TPE) molecule can be completely suppressed by the strong electron‐vibration couplings, i. e. the Franck‐Condon blockade effect. It is mainly associated with the low energy vibration modes, which is also the origin of the fluorescence quenching of the AIE molecule in solution. We further found that the conductance of the junction can be lifted by restraining the internal motion of the TPE molecule by either the methyl substitution on the phenyl group or by the aggregation, a mechanism similar to the AIE process. The present work demonstrates the correlation between optical process of molecules and quantum transport in their junction, and thus open a new avenue for the application of AIE type molecules in molecular electronics and functional devices.

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