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8 December 1995 Photoinduced absorption of conducting polymer-C60 composites
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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.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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);

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