Abstract
The photophysics of conducting polymers are of interest both for the fundamental information they provide about the nature of excitations in low-dimensional systems, and for the enormous practical potential they offer in the production of low cost, readily processible electroluminescent devices.[1-5] The technological goals in constructing organic LED's include improvement of the quantum efficiency of the luminescence and control over the emission frequency. By constructing new polymers with different side groups and doping polymer films with other luminescent molecules, both of these goals can be met. In this paper, we present ultrafast photophysical studies of a novel conjugated polymer with a high luminescence efficiency. Comparison of the transient absorption and emission dynamics of the new polymer, an alkyl-substituted poly(p-phenylenevinylene) (a-PPV), to unsubstituted or alkoxy-substituted PPV's [1-4] demonstrates that non-radiative pathways which compete with luminescent channels are significantly curtailed in the new material. Additional femtosecond studies on a-PPV/dye molecule blends show that rapid energy transfer takes place, opening the possibility for tuning the emission by the choice of dye molecule. Light emitting diodes constructed from the new polymer and the polymer/dye blends demonstrate improvement of the electroluminescence efficiency upon doping, verifying that energy transfer competes effectively with non-radiative channels under in-situ conditions.
© 1996 Optical Society of America
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