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Nat Commun. 2014 Apr 16;5:3646. doi: 10.1038/ncomms4646.

Visualization of exciton transport in ordered and disordered molecular solids.

Author information

1
Center for Excitonics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 13-3057, Cambridge, Massachusetts 02139, USA.
2
Queens College and Graduate Center, Department of Physics, The City University of New York, 6530 Kissena Boulevard, Flushing, New York 11367, USA.

Abstract

Transport of nanoscale energy in the form of excitons is at the core of photosynthesis and the operation of a wide range of nanostructured optoelectronic devices such as solar cells, light-emitting diodes and excitonic transistors. Of particular importance is the relationship between exciton transport and nanoscale disorder, the defining characteristic of molecular and nanostructured materials. Here we report a spatial, temporal and spectral visualization of exciton transport in molecular crystals and disordered thin films. Using tetracene as an archetype molecular crystal, the imaging reveals that exciton transport occurs by random walk diffusion, with a transition to subdiffusion as excitons become trapped. By controlling the morphology of the thin film, we show that this transition to subdiffusive transport occurs at earlier times as disorder is increased. Our findings demonstrate that the mechanism of exciton transport depends strongly on the nanoscale morphology, which has wide implications for the design of excitonic materials and devices.

PMID:
24736470
DOI:
10.1038/ncomms4646

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