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Degradation induced decrease of the radiative quantum efficiency in organic light-emitting diodes

: Schmidt, Tobias D.; Setz, Daniel S.; Flämmich, Michael; Scholz, Bert J.; Jaeger, Arndt; Diez, Carola; Michaelis, Dirk; Danz, Norbert; Brütting, Wolfgang


Applied Physics Letters 101 (2012), Nr.10, Paper 103301, 4 S.
ISSN: 0003-6951 (Print)
ISSN: 1077-3118
ISSN: 1931-9401 (online)
Fraunhofer IOF ()

The efficiency decrease during electrical operation of organic light-emitting diodes is a crucial issue for both applied and fundamental research. In order to investigate degradation processes, we have performed an efficiency analysis for phosphorescent state-of-the-art devices in the pristine state and after an accelerated aging process at high current density resulting in a luminance drop to less than 60% of the initial value. This loss in efficiency can be explained by a decrease of the radiative quantum efficiency of the light-emitting guest/host system from 70% to 40%, while other factors determining the efficiency are not affected.