Regensburg 2007 – wissenschaftliches Programm

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 8: Poster Session SYOE

SYOE 8.76: Poster

Dienstag, 27. März 2007, 18:00–20:00, Poster B

Thick Multilayer Devices for Potential Organic Laser Diodes — •Bodo Wallikewitz, Matthias de la Rosa, Dirk Hertel, and Klaus Meerholz — Universität zu Köln, Institut für Physikalische Chemie, Luxemburgerstr. 116, 50939 Köln

The performance of organic light emitting diodes (OLEDs) has made tremendous progress over the past decade, nevertheless the realization of organic laser diodes remains a challenge. To achieve lasing optical gain manifested by amplified spontaneous emission (ASE) is mandatory. We have investigated low ASE thresholds (5 uJ/cm2) and high gain (50 cm-1) of cross-linked conjugated copolymers. Crosslinkable materials can be structured to second order DFB gratings. Polymer lasers with the emitter and resonator made of the same material are investigated. The threshold of this polymer laser is 1.5 uJ/cm2. To realize an electrically driven laser it is necessary to confine the wave guided mode in the active layer in order to prevent losses induced by the metal contacts in the device. We obtained a low ASE threshold of 10 uJ/cm2 in an electrical contactable device by using thick emitter, 3electron and hole transport layers (HTL). Film thickness and refractive index were optimized for each layer. OLEDs are characterized and the influence of thick multilayers on OLEDs performance is discussed. The efficiency decreases from 9 Cd/A for a standard 100nm OLED to 5 Cd/A for a 1 um multilayer OLED. The ratio of the edge to top emission intensity increases for a factor of 14 for the 1 um multilayer OLED. Current densities of 500 A/cm2 are achieved for thick HTL and a mobility of 2x10-3 cm2/Vs is extracted.