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CPP: Chemische Physik und Polymerphysik

CPP 16: Electronic Structure and Spectroscopy II

CPP 16.10: Vortrag

Mittwoch, 29. März 2006, 17:00–17:15, ZEU 160

Amplified Spontaneous Emission of Cross-linkable Conjugated Polymers in Multilayer Devices — •Bodo Wallikewitz, Dirk Hertel, and Klaus Meerholz — Universität zu Köln, Luxemburgerstrasse 116, 50939 Köln

Although the performance of polymer and small organic light emitting diodes (OLEDs) has made tremendous progress over the past decade, electrically pumped organic laser diodes as an advanced application remain a challenge. To achieve lasing optical gain manifested by for instance amplified spontaneous emission (ASE) is mandatory. We investigated for the first time ASE properties, gain and loss of cross-linked conjugated copolymers. Cross-linkable materials offer the advantage of solution processing of thick multilayer devices, essential for future electric driven organic lasers. Furthermore we studied the influence of chromophore type and chromophore concentration on the ASE threshold, optical gain and loss. We obtained low thresholds below 5 uJ/cm2, high gain above 33 cm-1 and low losses below 5 cm-1. These are very low thresholds, even for conventional conjugated polymers described in the literature. Thick hole transport layers (HTL) are necessary to enable ASE and optimize mode confinement in the emitter material on quenching electrodes. We restored the properties of neat polymer films on electrodes by using a thick, cross-linked HTL in between. The threshold is minimized by optimizing the refractive index of HTL, HTL thickness and polymer thickness. Furthermore, electrical properties of HTLs and efficiencies of thick multilayer OLEDs are presented and discussed.