Regensburg 2000 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 23: Organische Schichten III

DS 23.3: Fachvortrag

Mittwoch, 29. März 2000, 16:00–16:15, H31

TIME EVOLUTION OF FLUORESCENCE IN ORGANIC THIN FILMS AND DEVICES — •Elmar Schreiber¹, Vladimir Bulović² und Stephen R. Forrest² — ¹Center for Ultrafast Laser Applications, Princeton University, NJ 08544, USA — ²POEM, Department of Electrical Engineering, Princeton University

Our investigation of time resolved fluorescence in organic thin films and organic light emitting devices (OLEDs) reveals large spectral shifts (up to 35 nm) during the first few nanoseconds of light emission. Both neat and doped organic films are excited by picosecond laser pulses and fluorescence response is detected by a streak camera (60 ps overall system response). We used Alq₃ and DCM2 as lumophores doped in NPD, TPD, Zrq₄, and Alq₃ hosts. The observed shifts occur over a time scale of < 5 ns and originate from the response of the medium to the excitation of the luminescent molecules. When the lumophore is promoted from the ground to the excited state, the change in magnitude and orientation of its dipole moment influences the surrounding molecules to minimize the total system energy. Our study demonstrates that local excitations can strongly influence the surrounding environment for polar lumophores in polar hosts.