Morphology dependent exciton formation in regioregular poly(3‐alkyl)thiophenes

Abstract

The photophysics of the regioregular (RR) poly(3‐alkylthiophene) (P3AT) films is investigated by cw‐photoinduced absorption (PIA) measurements based on bleaching signals. The photoexcitation intensity dependence of the cw‐PIA signals demonstrates that both photogenerated localized and delocalized polarons obey a bimolecular recombination process under cw photoexcitation. It is demonstrated that the lineshape of cw‐PIA bleaching spectra for the P3AT films varies with the length of the alkyl substituents of P3AT. The bleaching spectra reveal a trend that the electron‐phonon couplings of final exciton migration sites become strong with increasing the interlamella distance in the P3AT film. This indicates that interlamella couplings affect the electron‐phonon couplings of the migration sites locating at two‐dimensional lamellas. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)