Photoinduced infrared absorptions from conjugated polymers with nondegenerate ground states

Photoinduced infrared absorptions from poly( p-phenylene), poly( p-phenylenevinylene), poly(2,5-dioctyloxy-p- phenylenevinylene) and poly(2,5-thienylenevinylene) have been measured using the FT-IR difference-spectrum method. The observed photoinduced bands are attributable to photo-generated charged species which give rise to giant infrared intensities. The excitation-power dependences of the photoinduced absorption intensities can be explained by means of the bimolecular recombination of the positive and negative polarons that are formed from a polaron pair (interchain charge-transfer exciton) generated by photoirradiation.