FIELD-INDUCED EXCITON BREAKING IN CONJUGATED POLYMERS

We have investigated the held-induced quenching of photoluminescence in a film of poly(p-phenylphenylenevinylene) (PPPV) blended with polycarbonate (PC). Upon applying a dc field less than or equal to 3 X 10(6) V cm(-1) a reduction of the luminescence yield up to 30% is observed. Time-resolved photoluminescence measurements using the fs-upconversion technique show that the quenching effect evolves on a time scale 0.5 to similar to 100 ps after excitation. We explain this ultrafast temporal behavior of the quenching process in terms of a field-assisted dissociation of neutral singlet excitations into geminate electron-hole pairs while undergoing a random walk among polymer segments. Our model implies that photocarrier generation is a secondary process resulting from exciton dissociation.