Exciton dynamics in organic semiconductor devices: Investigation of exciton-charge carrier interactions as revealed by photoluminescence responses

We measured the photoluminescence decay curves of an organic semiconductor device when the device was electrically driven, and we investigated its exciton dynamics when there were a large number of electrons. The device consisted of a transparent electrode (indium tin oxide), a tris (8-quinolinolato) aluminum layer (Alq, 100 nm), and a metal cathode (Mg:Ag or Al, 200 nm). It was demonstrated experimentally that a singlet exciton of Alq was quenched by electrons through a bimolecular process. The rate constant of the PL quenching was estimated to be of the order of 10(-9) similar to 10(-10) cm(3)/s.