TIME-RESOLVED PHOTOLUMINESCENCE FROM POLY[2-METHOXY, 5-(2'-ETHYL-HEXYLOXY)-P-PHENYLENE-VINYLENE] - SOLUTIONS, GELS, FILMS, AND BLENDS

We present the results of time-resolved luminescence studies of poly[2 -methoxy, 5-(2'-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV), as a pure film, in solution, in a gel formed by a network of ultrahigh mole cular weight polyethylene (UHMW-PE), and in a blend with UHMW-PE. The luminescence has a characteristic lifetime of 200-300 ps at room tempe rature, increasing to 500-700 ps when the materials are cooled to 80 K ; the decay time is approximately the same for all the physical forms of the material (solution, film, gel, blend). The relatively short lif etimes, compared to intrinsic values calculated from absorption and em ission spectra, and the observed temperature dependence indicate that the luminescence decay is quenched by nonradiative processes. The time decay of the photoluminescence deviates from a single exponential for most forms of the MEH-PPV. Best fits to stretched exponential and dou ble exponential expressions are presented. Steady state photoluminesce nce spectra and integrated luminescence vs pump intensity data are pre sented in order to establish which of the possible mechanisms are most important.