M. G. Harrison, D. Fichou, F. Garnier and A. Yassar.
Optical Materials 9 (1998) p53-58 .
We have studied the charged excitations in a series of oligothiophenes of increasing conjugation length, namely a-6T, a-8T and substituted a-12T, in order to gain insight into how charge is stored in polythiophenes and to investigate how the polaron and bipolaron concepts relate to molecular cations and dications. We measured optical charge-modulation spectra of thin solid films of oligomers within field-effect diodes, because of the direct relevance to organic thin/film transistors and also the ability to induce unipolar charge carriers by purely electrostatic means, without introducing chemical dopants. By modulating the gate voltage and probing the resulting modulation of the optical absorption at the same frequency, we have observed optical transitions characteristic of the charged excitations of these oligomers in the solid state.
If you cannot find any of these papers, drop me a line for a reprint...
Ed.: G. Wegner and K. Müllen, V.C.H. Verlag
Chapter 10: Optical Applications
M. G. Harrison and R. H. Friend
"Optical Device Applications" in "HANDBOOK OF POLYTHIOPHENES"
Ed.: D. Fichou, Wiley–V.C.H. Verlag - in press)
M. A. Granström, M. G. Harrison and R. H. Friend.
Mark Harrison firstname.lastname@example.org, Marburg, May 3, 1998