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Chemical degradation processes of highly stable red phosphorescent organic light emitting diodes

 
: Moraes, I.R. de; Scholz, S.; Lüssem, B.; Leo, K.

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Organic Electronics 13 (2012), No.10, pp.1900-1907
ISSN: 1566-1199
English
Journal Article
Fraunhofer IKTS ()
degradation; LDI-TOF-MS; lifetime; OLED

Abstract
We investigate the chemical degradation processes of highly stable red organic light emitting diodes (OLEDs) based on the triplet emitter tris(1-phenylisoquinoline)iridium(III) by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS). The analysis of LDI-TOF spectra, collected on OLEDs driven at different current densities, shows a direct correlation between the lifetime of the devices and the formation of the three different reaction products: a BPhen dimer, an adduct of BPhen dimer with cesium, and the complex [BAlq 2+Al(Me-q) 2] + as well. Additionally it was possible to identify another degradation product, whose chemical structure is related to the alpha-NPD molecule as well to the fluorine of the used p-dopant. This product is only observable in devices aged at v ery high current densities.

: http://publica.fraunhofer.de/documents/N-208418.html