Electric field dependent generation of geminate electron–hole pairs in a ladder-type π-conjugated polymer probed by fluorescence quenching and delayed field collection of charge carriers

We report on measurements of electric field induced fluorescence quenching Φ and optical charge generation η by using the time-delayed-collection-field technique (TDCF). The material under investigation is the methyl-substituted ladder-type poly(para-phenylene) (MeLPPP), a π-conjugated polymer characterized by low intrachain disorder. Fluorescence quenching Φ of up to 50% is observed. The field dependence of both Φ and η is associated with the primary step in charge generation, i.e., exciton dissociation into geminate electron–hole pairs rather than their full dissociation into free charge carriers. This is at variance with the basic assumption in Onsagerʹs theory of charge generation.