Direct imaging of exciton transport in tubular porphyrin aggregates by Ultrafast microscopy

Wan, Y., Stradomska, A., Knoester, J. and Huang, L. (2017) Direct imaging of exciton transport in tubular porphyrin aggregates by Ultrafast microscopy. Journal of the American Chemical Society, 139(21), pp. 7287-7293. (doi: 10.1021/jacs.7b01550) (PMID:28480703)

Abstract

Long-range exciton transport is a key challenge in achieving efficient solar energy harvesting in both organic solar cells and photosynthetic systems. Self-assembled molecular aggregates provide the potential for attaining long-range exciton transport through strong intermolecular coupling. However, there currently lacks an experimental tool to directly characterize exciton transport in space and in time to elucidate mechanisms. Here we report a direct visualization of exciton diffusion in tubular molecular aggregates by transient absorption microscopy with ∼200 fs time resolution and ∼50 nm spatial precision. These direct measurements provide exciton diffusion constants of 3-6 cm(2) s(-1) for the tubular molecular aggregates, which are 3-5 times higher than a theoretical lower bound obtained by assuming incoherent hopping. These results suggest that coherent effects play a role, despite the fact that exciton states near the band bottom crucial for transport are only weakly delocalized (over <10 molecules). The methods presented here establish a direct approach for unraveling the mechanisms and main parameters underlying exciton transport in large molecular assemblies.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Stradomska-Szymczak, Dr Anna
• Authors: Wan, Y., Stradomska, A., Knoester, J., and Huang, L.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of the American Chemical Society
• Publisher: American Chemical Society
• ISSN: 0002-7863
• ISSN (Online): 1520-5126
• Published Online: 08 May 2017
• Copyright Holders: Copyright © 2017 American Chemical Society
• First Published: First published in Journal of the American Chemical Society 139(21):7287-7293
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher