New evidence of long-lived photoexcited charged states in thin films of PDA-4BCMU

We report results of steady-state photoinduced absorption experiments on PD A-4BCMU grown on silica substrate. We observe three photoinduced absorption bands at 0.82, 0.95 and 1.39 eV whose relaxation dynamics indicate that th e first two are due to charged states while the third is originated by trip let excitons. The photogeneration of both charged and neutral states in PDA -4BCMU previously observed in polycarbazolyldiacetylenes, indicates that th is is a general feature of polydiacetylenes. The relative weight of one exc ited species over the other one is influenced by the molecular and supramol ecular organization of the polymer.