Ultrafast on-chain dissociation of hot excitons in conjugated polymers

Abstract

A model describing field-assisted on-chain dissociation of hot optical excitations in conjugated polymers is developed. It rests on the notion that excess photon energy is required for the onset of intrinsic charge-carrier photogeneration. Conversion of this energy into excited vibrational modes within a conjugated polymer segment leads to temporal overheating. The vibrational heat bath is considered as the main source of the energy that allows charge carriers to escape from the potential well formed by Coulomb and external electric fields. Although the quantum yield of carrier photogeneration strongly increases with increasing external field, it reveals an anomalously weak temperature dependence in quantitative agreement with experimental data on a ladder-type poly-para-phenylene and on a polyphenylenevinylene derivative.