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Oleg Mirzov

System architect

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Photoluminescence spectra of a conjugated polymer: from films and solutions to single molecules

Author

  • Oleg Mirzov
  • Ivan Scheblykin

Summary, in English

The purpose of this work is to address the issue of applicability of single-molecule spectroscopy (SMS) results for conjugated polymers to "bulk" samples, e.g. conjugated polymer films. Also, some apparent inconsistencies in the literature on SMS regarding the photoluminescence spectral position of conjugated polymers are discussed. We present a series of photoluminescence spectra of thin films of the conjugated polymer poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) with a wide range of varying thickness. The thickness was varied from similar to 20 nm to the value corresponding to well-separated single molecules (SMS sample). The thickness variation resulted in a strong (similar to 2000 cm(-1)) blue-shift and broadening of the spectrum. The result was reproduced on isolated molecules embedded into a PMMA matrix. This effect cannot be explained by a decrease in energy transfer "freedom" alone. We performed a comprehensive comparison of presented and elsewhere published spectra of MEH-PPV polymer and oligomers in different samples: films, solutions, isolated-molecule coatings and standard SMS samples. The comparison allows that the main reason behind the blue shift is conformational disorder, which is largely dependent on the sample. We also discuss some experimental aspects of SMS, such as representativeness of detected molecules, spectral sensitivity of a setup and temperature. Together with differences in sample preparation method, these issues can explain the existing inconsistencies in the literature.

Department/s

  • Chemical Physics

Publishing year

2006

Language

English

Pages

5569-5576

Publication/Series

Physical Chemistry Chemical Physics

Volume

8

Issue

47

Document type

Journal article

Publisher

Royal Society of Chemistry

Topic

  • Atom and Molecular Physics and Optics

Status

Published

ISBN/ISSN/Other

  • ISSN: 1463-9084