Supramolecular nanofibers paired with nanohole substrate improve exciton transport in organic solid

Researchers at Science Tokyo have discovered that self-assembling anthracene-based supramolecular nanofibers, when paired with plasmonic gold nanohole substrates, can dramatically improve exciton transport in organic semiconductors. Excitons are fleeting entities created when light is absorbed, and they diffuse through the material before dissociating into free charge carriers to generate electricity.

However, conventional organic semiconductors typically limit exciton diffusion to just 5-20 nm before recombination, stifling device performance. The novel approach involved designing BPEA-based molecules with amide groups to promote self-assembly through hydrogen bonding, leading to highly ordered J-aggregates. These nanofibers demonstrated exciton migration distances of up to 350 nm and diffusion coefficients of 0.7 cm²/s, among the highest reported for organic solids.

By introducing plasmonic nanohole substrates, the research team further boosted exciton diffusion to 1.3 cm²/s and extended transport lengths beyond 550 nm when nanofibers were aligned with the nanohole lattice. Quantum calculations revealed that excitons are delocalized across two to three neighboring molecular units, while significant mixing between excited and charge-transfer states strengthens electronic coupling.

The study, published in Nano Letters, demonstrates a promising strategy for enhancing energy transport in organic materials, potentially paving the way for improved optoelectronic devices.