EXCIMERS IN LIGHT-EMITTING CONJUGATED POLYMERS

The electronic structures of the low-lying excited states for two para llel chains of poly (p-phenylene-vinylene) with arbitrary relative pos itions are studied. The interchain interaction is treated microscopica lly. The energy and charge transfer fraction of the (light-emitting) l owest singlet state are found to depend sensitively on the horizontal shift of the two chains, which is in turn determined by the packing ge ometry. Our predictions of the excimer-forming geometry and the relati ve (dipole-forbidden) photoluminescence lifetimes are in excellent agr eement with experiments.