Field-induced exciton breaking in conjugated polymers

Abstract

We have investigated the field-induced quenching of photoluminescence in a film of poly(p-phenylphenylenevinylene) (PPPV) blended with polycarbonate (PC). Upon applying a dc field \ensuremath{\le}3\ifmmode\times\else\texttimes\fi{}${10}^{6}$ V ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ 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 \ensuremath{\sim}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.