Excited states in PPP-type ladderpolymers probed by photoinduced absorption

We present photoinduced absorption (PIA) measurements done on a planarized form of poly(para-phenylene) (PPP). Macromolecules of different degree of polymerization and with a chemical modification at the bridge, connecting the benzene rings of the PPP-backbone, are investigated. There is clear evidence that the quasi steady state PIA signal in the near infrared vanishes with increasing intrachain order. We discuss the stabilization of the photogenerated defects. The nature of the observed states is described based on their characteristic electronic absorptions, their lifetime and their temperature dependence.