Dependence of Coumarin6 concentration on electroluminescent properties in molecular dispersion type polymer light emitting diode

Abstract

It was found that luminescent characteristics of PVCz based polymer light-emitting diode are significantly influenced by the doping of Coumarin6(C6) into the host matrix. The device exhibits a maximum luminance and pure green emission with peak wavelength of 510nm at about lwt.% of C6. In contrast, the threshold voltage increases monotonically with C6 concentration at least within 10.3wt.%. We additionally found three kinds of excitation bands, which are originated in energy transfer process from the host(PVCz),electron transporting material(Alq3) and direct excitation of emission center(C6) respectively. The efficiency was improved by a factor of one and half in the optimized C6 concentatin.