Charge carrier photogeneration in conjugated polymer

The electric field-assisted charge carrier photogeneration in a Ladder-Type Methyl substituted Poly(Para-Phenylene) was investigated by studying the electromodulated ultrafast transient differential absorption spectra and kinetics. The field stimulated appearance of the polaron absorption and quenching of the singlet exciton absorption proves that dissociation of excitons into geminately bound electron-hole pairs occurs within the entire exciton lifetime and proceeds from the relaxed state. An influence of the optically created excitons and charge pairs on the Stark-shift of the absorption band was observed and interpreted as caused by the modification of the dielectric constant of the medium. The initial separation distance of the charge carriers and its evolution in time were determined from the Stark-shift dynamics. The initial separation distance was obtained being slightly larger than the distance between adjacent polymer chains.