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K-band ESR studies of structural anisotropy in P3HT and P3HT/PCBM blend polymer solid films: Paramagnetic defects after continuous wave Xe-lamp photolysis

K-Band Elektron-Spin-Resonanzuntersuchungen der strukturellen Anisotropie von P3HT und P3HT/PCBM Polymerfilmen
: Konkin, A.; Roth, H.-K.; Scharff, P.; Aganov, A.; Ambacher, O.; Sensfuss, S.


Solid State Communications 149 (2009), Nr.21-22, S.893-897
ISSN: 0038-1098
Fraunhofer IAF ()
ESR; measurement; Messung; polymer blend; Polymerkomposite; polymer solar cell; Polymer-Solarzelle

Kappa-band electron spin resonance (ESR) technique was employed to study films of regioregular poly(3-hexylthiophene) (P3HT) and P3HT/PCBM ([6,6]-phenyl-C(ind 61)-butyric acid methyl ester) blends to estimate their structural macroscopic anisotropy. As for nematic liquids (or liquid crystals) our consideration was based on the approach that the free energy of self-organised polymer molecules of P3HT is a function of molecular orientation and therefore chains in polymer films exhibit some degree of orientational order. The lamellar molecular orientation of the films was confirmed by angular-dependent ESR spectroscopy of polarons, which were considered as a localised paramagnetic centre with an unpaired carbon Pi-electron of the thiophene ring. The additional ESR signal initiated by the UV/visible CW Xe-lamp illumination of the films at air atmosphere was attributed to the negative polaron (trapped photo-electron) on the polymer chain, as well as to the radical due to chain degradation.