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ESR and ESE studies on polymer semiconductors of weakly doped poly(tetrathiafulvalene)
Author(s) -
Roth H.Klaus,
Brunner Winfried,
Völkel Georg,
Schrödner Mario,
Gruber Harald
Publication year - 1990
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19900340121
Subject(s) - polaron , doping , conductivity , tetrathiafulvalene , electron paramagnetic resonance , semiconductor , paramagnetism , radical , polymer , electrical resistivity and conductivity , materials science , conductive polymer , organic semiconductor , condensed matter physics , saturation (graph theory) , chemistry , electron , nuclear magnetic resonance , optoelectronics , molecule , organic chemistry , physics , quantum mechanics , combinatorics , mathematics , composite material
In the studied poly(tetrathiafulvalenes), PTTF, the TTF units are linked via phenyl groups or via tetrahydroanthracene bridges. The PTTF are doped with oxygen and with iodine respectively. The electrical conductivity strongly depends on temperature as it is typical of semiconducting materials. The existence of various types of paramagnetic centres is confirmed by ESR saturation experiments, by spectra simulation and by electron spin echo (ESE) measurements in the temperature region of 2 K to 400 K. At room temperature the doped PTTF have a dc conductivity between 10 −9 Scm −1 and 10 −4 Scm −1 . Relations between the concentration of various radicals and the electrical conductivity of the polymers are discussed by means of a model based on mobile and immobile radicals, polarons and bipolarons. There are experimental indications for temperature‐dependent formation and break‐up of bipolarons which are discussed in the paper.