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Measurements of Photo-Induced Changes in Conjugated Polymers

Published online by Cambridge University Press:  21 February 2011

Carleton H. Seager ,
Michael B. Sinclair ,
D. Mc Branch ,
A. J. Heeger  and
G. L. Baker
Carleton H. Seager
Affiliation:
Sandia National Laboratories, Albuquerque, N. M.
Michael B. Sinclair
Affiliation:
Sandia National Laboratories, Albuquerque, N. M.
D. Mc Branch
Affiliation:
University of California at Santa Barbara, Santa Barbara, Ca.
A. J. Heeger
Affiliation:
University of California at Santa Barbara, Santa Barbara, Ca.
G. L. Baker
Affiliation:
Bell Communications Research, Red Bank, N. J.
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Abstract

We have used the highly sensitive technique of Photothermal Deflection Spectroscopy (PDS) to measure changes in the infra-red absorption spectra of MEHPPV, P3HT and Polydiacetylene-4BCMU induced by pumping these polymers with light above the π - π* transition energy. In contrast to previous chopped light transmission measurements of these effects, the PDS technique can directly measure the buildup or decay of the absorption coefficient, m, on the time scale of seconds to days. In the case of MEHPPV we observe that above-gap light causes the appearance of a broad infra-red peak in α, which continues to grow-in hours after the pump light is first applied. For this polymer the general shape of the absorption spectra in the unpumped state mimics the photo-induced changes, suggesting that remnant photo-induced states determine the maximum transparency observed under normal experimental conditions. For P3HT and to a lesser extent, MEHPPV, we also observe irreversible photo-induced absorption components which we tentatively identify with photo-induced oxidation of the polymer matrix.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 228: Symposium N – Materials for Optical Information Processing , 1991 , 73
Copyright
Copyright © Materials Research Society 1992

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References

REFERENCES

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