QUANTUM EFFICIENCIES OF ELECTROLUMINESCENT POLY(PARA-PHENYLENES)

Poly(para-phenylene) (PPP) and its derivatives with their band-gap cor responding to blue light have shown to be suitable as active layers in Light Emitting Diodes (LEDs). One important factor for the efficieny of these devices is the photoluminescence quantum yield of the active layer. Intermolecular effects in the layers (excitation energy transfe r (EET), self-quenching and excimer-formation) lead to a decreased qua ntum yield in solid state compared to solutions. We investigated the p hotoluminescence quantum yields of para-hexaphenyl and several PPP-typ e ladderpolymers in solution and solid state. We report on the measure d quantum yields (up to 85% in solution and 30% in solid state) and di scuss the occuring quenching mechanisms.