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

Abstract

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 (≈0.001%) pulsed electroluminescence measurements with electric fields up to 1×109 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, approaching Ohmic-like behavior. We report current densities of 100 A/cm2 and brightnesses of 7×105 cd/m2. The spectral features are monitored below the onset of degradation.