Regensburg 2010 – scientific programme
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DS: Fachverband Dünne Schichten
DS 45: Organic Thin Films II
DS 45.1: Talk
Friday, March 26, 2010, 12:00–12:15, H8
OLEDs under high current densities — •Daniel Kasemann, Hartmuth Fröb, and Karl Leo — Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden, Germany
Organic solid state lasers combine the flexibility of organic materials with the technological advantages of a solid state light emitter. Various optically pumped devices have been shown, comprising different resonator types like DFB and VCSEL design. Nevertheless, direct electrical pumping has not been achieved yet. The main obstacle here is the high excitation density needed in the active layer. The inversion is easily created by pulsed optical pumping, but additional losses prevent the excitation to reach the critical point when driven electrically.
To estimate the dimensions of the additional losses, we investigate full pin-OLEDs under high current densities and compare the behaviour of singlet and triplet emitter materials. The singlet emitter system uses Alq3 doped by DCM as emitting layer. The triplet system is an efficient OLED based on α-NPD doped by Ir(MDQ)2(acac), a red phosphorescent emitter[1]. In pulsed operation, these devices sustain current densities in the range of kA/cm2 without the need of additional cooling of the sample. To obtain an insight in the behaviour in this operation range, we compare power dependent emission spectra as well as electro-induced absorption (EIA) measurements at high current densities.
[1] R. Meerheim et al., J. Appl. Phys. 104, 014510 (2008)