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Published on: June 18, 2013
How strain controls electronic linewidth in single beta-phase polyfluorene nanowires.
Enrico Da Como1, Klaus Becker, Jochen Feldmann
1Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig-Maximilians-Universität, Amalienstrasse 54, D-80799 Munich, Germany. Enrico.Dacomo@physick.uni-muenchen.de
Nano Letters
|September 1, 2007
Summary
Extended polyfluorene chains form pure, defect-free beta-phase crystals. Chain shape influences phase formation, and bending in these planarized chains affects their optical properties without disrupting conjugation.
Area of Science:
- Materials Science
- Polymer Chemistry
- Spectroscopy
Background:
- Polyfluorenes are widely studied for their optoelectronic applications.
- The crystalline beta-phase of polyfluorene is desirable for its unique properties.
- Understanding factors controlling beta-phase formation and its impact on optical properties is crucial.
Purpose of the Study:
- To investigate the formation of the one-dimensional crystalline beta-phase of polyfluorene.
- To correlate polymer chain shape with beta-phase formation.
- To characterize the optical properties of beta-phase polyfluorene, particularly the effect of chain bending.
Main Methods:
- Low-temperature single-molecule fluorescence spectroscopy.
- Analysis of polymer chain conformation and its relation to phase formation.
- Measurement of transition linewidth and excited-state dephasing times.
Main Results:
- Pure, virtually defect-free beta-phase polyfluorene chains were observed.
- Extended initial polymer chain shapes preferentially form the planarized beta-phase.
- Chain bending within the plane increases transition linewidth but preserves pi-electron conjugation.
- Electronic dephasing time of the excited state is >3 ps at 5 K.
Conclusions:
- Polymer chain conformation is a critical factor in forming defect-free beta-phase polyfluorene.
- Chain bending in beta-phase polyfluorene does not disrupt conjugation, challenging assumptions about polarization.
- Spectroscopic signatures can identify planarized chains and their bending, offering insights into charge transport and emission properties.
