Photoexcitations in disubstituted acetylene polymers

Martin Liess; Ilarie I. Gontia; Toshio Masuda; Katsumi Yoshino; Z. Valy Vardeny

doi:10.1117/12.295529

1 December 1997 Photoexcitations in disubstituted acetylene polymers

Martin Liess, Ilarie I. Gontia, Toshio Masuda, Katsumi Yoshino, Z. Valy Vardeny

Proceedings Volume 3145, Optical Probes of Conjugated Polymers; (1997) https://doi.org/10.1117/12.295529
Event: Optical Science, Engineering and Instrumentation '97, 1997, San Diego, CA, United States

Abstract

We have used a variety of optical techniques to study the photoexcitation dynamics in several disubstituted acetylene polymer thin films. We found that although these polymers have a degenerate ground state, as determined by iodine doping and C₆₀ photodoping, they show strong photoluminescence in the blue/green spectral range with high quantum efficiency in thin films. The cw photo modulation spectrum contains a single photoinduced absorption (PA) band at 1.7 eV with monomolecular recombination kinetics with a lifetime of 25 ms. PA detected magnetic resonance (PADMR) shows that this PA band is related to spin 1/2 excitations, which therefore identifies it as due to neutral soliton antisoliton pairs (S^o, S^o), similar to the 1.35 eV PA band in t-(CH)_x. No triplet PADMR signal was observed and we therefore conclude that triplet excitations are unstable in disubstituted acetylene polymers, even though singlet excitons relatively stable. We consider therefore a possible S^o photogeneration mechanism via singlet to triplet intersystem crossing, followed by triplet exciton decomposition into S^o S^o pairs. Also we detected polarons in a degenerate ground state polymer for the first time.

Citation Download Citation

Martin Liess, Ilarie I. Gontia, Toshio Masuda, Katsumi Yoshino, and Z. Valy Vardeny "Photoexcitations in disubstituted acetylene polymers", Proc. SPIE 3145, Optical Probes of Conjugated Polymers, (1 December 1997); https://doi.org/10.1117/12.295529

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