Degradation of phosphorescent organic light-emitting diodes under pulsed current stressing

Abstract

The electrical and optical degradation of green phosphorescent organic light-emitting diodes (OLEDs) stressed under 50mA/cm2 pulsed currents with 10–50% duty cycles was studied. The stressing resulted in significant increases in low-bias leakage current and operational voltage. The luminance evolution comprised an initial rapid decay regime and a subsequent slow decay regime, and only the latter was governed predominantly by electrical excitation. Compared to continuous-wave stressing, pulsed stressing with 10% duty cycle improved the effective half life by only ∼15%, indicating that self-heating plays a minor role in the performance degradation process. Adding a reverse bias component to the pulsed current led to suppressed low-bias leakage and current-induced luminance decay due to defect removal and alleviated charge build-up.