Web Release Date: August 31,
How Strain Controls Electronic
Linewidth in Single 
-Phase
Polyfluorene Nanowires
and
Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig-Maximilians-Universität, Amalienstrasse 54, D-80799 Munich, Germany, and Department of Physics, University of Utah, Salt Lake City, Utah 84112
Received May 22, 2007
Revised July 20, 2007
Abstract:
Low-temperature single-molecule fluorescence spectroscopy reveals pure, virtually defect-free chains of the one-dimensional crystalline -phase
of polyfluorene. The likelihood of -phase formation is shown to correlate directly with the initial shape of the polymer chain, with extended
chains preferentially forming this planarized phase. Planarized chains, characterized by a distinct spectroscopic signature can, however,
exhibit substantial bending within the plane. This bending results in a strong increase in the elementary transition linewidth of the conjugated
segment. The transition linewidth provides a lower limit to the electronic dephasing time of the excited state of >3 ps at 5 K. Remarkably,
bending does not appear to disrupt the 
-electron conjugation so that the emission from a single bent -phase chromophore is not necessarily
linearly polarized as is generally assumed.
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