Photoinduced absorption of conducting polymer-C60 composites

Esther M. Conwell; Howard A. Mizes; Jerry Perlstein

doi:10.1117/12.228106

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8 December 1995 Photoinduced absorption of conducting polymer-C₆₀ composites

Esther M. Conwell, Howard A. Mizes, Jerry Perlstein

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Proceedings Volume 2530, Fullerenes and Photonics II; (1995) https://doi.org/10.1117/12.228106
Event: SPIE's 1995 International Symposium on Optical Science, Engineering, and Instrumentation, 1995, San Diego, CA, United States

Abstract

Experimental studies of photoinduced absorption, PA, have been carried out by several groups on composites of C₆₀ with conducting polymers such as poly[2-methoxy, 5-(ethyl hexyloxy) -p- phenylene vinylene], MEH-PPV, to understand the quenching of photoluminescence and increase of photoconductivity caused by the addition of small amounts of C₆₀. To account for the observed PA it is first necessary to know where the C₆₀ molecules sit relative to the MEH-PPV chains. We found with the use of a Monte Carlo cooling algorithm that the most probable position of the C₆₀ is in a channel formed by the alkoxy side chains, its center approximately 10 angstrom from that of the MEH-PPV backbone. We identify the PA peak seen in MEH-PPV as the transition between the lower and upper levels of a polaron coupled to one of opposite sign on a neighboring chain. Calculations are carried out for the energy levels of neutral C₆₀ and C₆₀^- using a tight binding Hamiltonian with the parameters obtained by Harigaya. To determine the effect on the levels of the Coulomb interaction between C₆₀^- and a positively charged polaron, P⁺, on MEH-PPV we use coupled equations. Finally, we suggest that the peak of the PA in the composite is due to transitions between the two polaron levels of a free P⁺ on MEH-PPV. Additional PA features in the composite can be identified as due to C₆₀^- and neutral C₆₀.

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Esther M. Conwell, Howard A. Mizes, and Jerry Perlstein "Photoinduced absorption of conducting polymer-C₆₀ composites", Proc. SPIE 2530, Fullerenes and Photonics II, (8 December 1995); https://doi.org/10.1117/12.228106

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