Photoluminescence quenching in poly(p-phenylene vinylene) derivatives

We investigated the photoluminescence (PL) quenching of the copolymer, poly(2,5-dimethyl-phenylenevinylene-co-2-methoxy-5-hexyloxy-phenylenevinylene (DMPPV-co-MHOPPV), focusing on the difference between pure films and copolymer-poly(ethylene oxide) (PEO) blends with and without applied bias in the LEDs. PL quenching of DMPPV-co-MHOPPV is decreased by dispersion in an inert host, PEG. Results show that the introduction of alkyl groups in the main backbone or copolymer, which can affect the interaction of polymer chain, and the PL quenching, can be decreased due to the decreasing of dissociation of bound excitons and limiting excitions to migrate quenching sites. In the LEDs, by studying the different PL quenching with the negative and positive bias, we infer that the internal field in the LEDs decreases the probability of dissociation of bound excitons. Our experimental results suggest that by means of tuning the chemical structure of polymers and the internal field of LEDs, the dissociation of excitons will be controlled and the luminescence quantum yield can be improved. (C) 2000 Elsevier Science B.V. All rights reserved.