Berlin 2005 – scientific programme

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SYOO: Organic Optoelectronics and Photonics

SYOO 6: Poster

SYOO 6.4: Poster

Monday, March 7, 2005, 18:00–20:00, Poster TU A

Differential reflectance and photoluminescence study on highly ordered thin films: PtOEP on potassium bromide — •Thomas Dienel, Holger Proehl, Karl Leo, and Torsten Fritz — Institut für Angewandte Photophysik, TU Dresden, Germany

The platinum-2,3,7,8,12,13,17,18-octaethylporphyrine (PtOEP) is one of the triplet emitting molecules used in organic electroluminescent devices like OLEDs. The interaction of long-living triplet-states of excited molecules reduces the number of radiative decays. To investigate effects like triplet-triplet-annihilation, we deposited ultra thin PtOEP films on potassium bromide (KBr) by means of organic molecular beam epitaxy (OMBE). In situ differential reflectance spectroscopy (DRS) and in situ photoluminescence (PL) were used to observe the spectral changes during the film growth. For the transparent substrate KBr, the DRS signal strongly resembles the absorption of the adsorbed molecules. The spectra of one monolayer PtOEP show a characteristic shape known for PtOEP molecules dissolved in trichloromethane. The phosphorescence of the PtOEP thin films, excited by a frequency-doubled Nd-YAG laser (532 nm), exhibits a new low energy feature [1], besides the well known triplet emission at around 650 nm. We used precipitation from PtOEP solutions to verify that the appearance of this new feature is indeed an aggregation effect.

[1] T. Dienel et al., J. Lum., accepted for publication (2004).