Harnessing Aggregation-Induced Quantum Interference in Molecular Junctions for Enhanced Electron Transport

Noncovalent stacking interactions, particularly π-π stacking, play a vital role in chemistry, biology, and organic optoelectronics. A deep understanding and precise control of these interactions are essential for molecular design and the development of functional devices. Here, we demonstrate an often-overlooked strategy for regulating electron transport in aromatic molecular junctions through solution-concentration-controlled molecular aggregation. By leveraging the intrinsic π-π stacking tendency of aromatic molecules in solution, we successfully guided <i>meta</i>- and <i>para</i>-substituted aromatic rings to form dual-anchored π-stacked dimer junctions simply by adjusting the concentration (from 10^-7 M to 10^-3 M). In contrast to widely reported parallel-displaced π-stacked dimer junctions─which typically exhibit significantly lower conductance than their monomeric counterparts─the concentration-induced dual-anchored π-stacked dimer junctions achieved up to a 700% increase in conductance. Flicker noise analysis revealed that these high-concentration parallel-stacked dimers not only contribute substantially to through-space charge transport but also effectively modulate the destructive quantum interference effect originally present in the <i>meta</i>-connected single-molecule junctions. Theoretical calculations further confirmed that the intermolecular interactions in parallel-stacked structures reshape the charge transport pathways and alter the quantum interference characteristics. This work experimentally introduces the concept of "aggregation-induced modulation" into the field of molecular electronics, offering a new theoretical and experimental foundation for developing solution-processable and smart-responsive molecular electronic devices.