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Subgap Absorption in Conjugated Polymers

Published online by Cambridge University Press:  21 February 2011

M. Sinclair
Affiliation:
Sandia National Laboratories, Albuquerque, NM
C. H. Seager
Affiliation:
Sandia National Laboratories, Albuquerque, NM
D. McBranch
Affiliation:
University of California, Santa Barbara, CA
A. J. Heeger
Affiliation:
University of California, Santa Barbara, CA
G. L. Baker
Affiliation:
Bell Communications Research, Red Bank, NJ
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Abstract

Along with χ(3), the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of < 10-5, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of “transparent” materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly[1,4-phenylenevinylene] (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm-1 to 10 cm-1. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration or fluorination.

Type
Research Article
Copyright
Copyright © Materials Research Society 1992

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References

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