Msa. Abdou et al., INTERACTION OF OXYGEN WITH CONJUGATED POLYMERS - CHARGE-TRANSFER COMPLEX-FORMATION WITH POLY(3-ALKYLTHIOPHENES), Journal of the American Chemical Society, 119(19), 1997, pp. 4518-4524
Molecular oxygen forms a reversible charge transfer complex (CTC) with
poly(3-alkylthiophenes). The complex is weakly bound but possesses a
distinct absorption band in the visible region. The electronic propert
ies of the neutral polymer are modulated by the CTC. The extent of mod
ulation of these properties is proportional to oxygen pressure and is
fully reversible. Analysis of poly(3-hexylthiophene) field effect tran
sistors under increasing pressures of oxygen shows that the carrier co
ncentration increases, conductivity increases, and the charge carrier
mobility is lowered by the formation of the charge transfer complex. T
he CTC manifests itself as a fluorescence quencher of mobile polaronic
excitons, and it explains why oxygen quenches luminescence with much
greater efficiency than predicted by a collisional quenching model. Im
plications of the charge transfer complex on the photochemistry of pol
y(3-alkylthiophenes) and photosensitization of singlet oxygen are disc
ussed.