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HL: Fachverband Halbleiterphysik

HL 52: Organic semiconductors II

HL 52.1: Vortrag

Freitag, 27. März 2009, 10:15–10:30, POT 51

Influence of electrical stress on hole transport in Poly(p-phenylenevinylene) — •Katja Stegmaier, Arne Fleißner, Christian Melzer, and Heinz von Seggern — Electronic Materials Department, Institute of Materials Science, TU Darmstadt, Petersenstraße 23, 64287 Darmstadt, Germany

One of the most prominent class of materials used as organic luminescent layer in large-area applications are derivatives of Poly(p-phenylenevinylene) (PPV). Organic light-emitting diodes (OLEDs) comprising such a polymeric semiconductor still disclose a degradation of the device performance under device operation limiting its applicability. Up to now, the processes taking place during this electrical fatigue are not fully understood. Different approaches to explain the increase of impedance and the loss of luminescence have been proposed.

For the first time the influence of electrical fatigue on the hole transport properties of different derivatives of PPV is investigated on bipolar PPV-based test structures similar to real OLED devices by the optical time-of-flight (TOF) technique. The utilized PPV layer thicknesses are in the order of microns and therewith considerably thicker than those of conventional OLEDs. TOF measurements on these structures before and after electrical treatment reveal a pronounced difference in hole transport. Due to electrical stressing under constant current hole transport becomes dispersive and hole mobility is reduced. The method of thermally stimulated currents (TSC) is employed to determine the trap structure in order to clarify the reasons for the variation in hole transport of the electrically fatigued OLEDs.