Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 41: Organic semiconductors

HL 41.8: Talk

Thursday, February 28, 2008, 17:00–17:15, ER 270

Optical Pumped Electrical Functional Organic Laser Device — •Bodo Wallikewitz, Matthias de la Rosa, Jonas Kremer, Dirk Hertel, and Klaus Meerholz — Universität zu Köln, Chemie Department, 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 obtained low ASE thresholds (5 uJ/cm2) and high gain (50 cm-1) in oxetane-based photo-crosslinkable conjugated copolymers. Due to their photoresist properties, these materials can be structured by second-order DFB resonator through holographic exposure. Optically pumped single layer polymer lasers with the emitter and resonator made of the same material are investigated and the coupling mechanism is discussed. To realize an organic laser diode it is necessary to confine the waveguided mode in the active layer (gain medium) and to prevent losses induced by the metal contacts in the device. An electrical functional laser device and an ASE device with a threshold of 4.5 and 9 uJ/cm2 was enabled by using thick crosslinked hole transport layer (X-HTL) and non-crosslinked electron transport layer (ETL) cladding the functional emitter 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 "thin" OLED to 5 Cd/A for a 1 um "thick" multilayer OLED.