Current-voltage characteristics of single layer polymer light emitting diodes under high intensity electrical excitation

We study the current-voltage characteristics of both double and single carrier polymer light emitting devices in the high intensity electrical excitation regime. Single layer devices are investigated with the orange-emitting MEH-PPV as the active polymer. Performing very low duty (approximate to 0.001 %) pulsed electroluminescence measurements with electric fields up to 1*10(9) V/m, we observe for the hole-dominated devices a space charge limited current with a saturating mobility and a saturating external quantum efficiency of 1%. For double carrier devices, the current starts to saturate in the high-field regime, appoaching Ohmic-like behavior. We report current densities of 100 A/cm(2) and brightnesses of 7*10(5) cd/m(2). The spectral features are monitored below the onset of degradation.