Document Type

Article

Language

eng

Format of Original

6 p.

Publication Date

8-4-2016

Publisher

American Chemical Society

Source Publication

Journal of Physical Chemistry Letters

Source ISSN

1948-7185

Original Item ID

DOI: 10.1021/acs.jpclett.6b01268; PubMed Central PMID: 27409718

Abstract

Understanding the mechanisms of long-range energy transfer through polychromophoric assemblies is critically important in photovoltaics and biochemical systems. Using a set of cofacially arrayed polyfluorenes (Fn), we investigate the mechanism of (singlet) exciton delocalization in π-stacked polychromophoric assemblies. Calculations reveal that effective stabilization of an excimeric state requires an ideal sandwich-like arrangement; yet surprisingly, emission spectroscopy indicates that exciton delocalization is limited to only two fluorene units for all n. Herein, we show that delocalization is determined by the interplay between the energetic gain from delocalization, which quickly saturates beyond two units in larger Fn, and an energetic penalty associated with structural reorganization, which increases linearly with n. With these insights, we propose a hopping mechanism for exciton transfer, based upon the presence of multiple excimeric tautomers of similar energy in larger polyfluorenes (n ≥ 4) together with the anticipated low thermal barrier of their interconversion.

Comments

Accepted version. Journal of Physical Chemistry Letters, Vol. 7, No. 5 (August 4, 2016): 2915-2920. DOI. © 2016 American Chemical Society. used with permission.

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