Dresden 2017 – scientific programme

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DS: Fachverband Dünne Schichten

DS 44: Postersession II

DS 44.45: Poster

Thursday, March 23, 2017, 17:00–19:00, P1C

Investigation of Charge Carrier Distribution in OLEDs by Means of Photoluminescent Molecular Probes — •Thomas Ferschke¹, Lars Jäger², Wolfgang Brütting², and Jens Pflaum^1,3 — ¹Experimental Physics VI, Julius Maximilian University, 97074 Würzburg — ²Institute of Physics, University of Augsburg, 86135 Augsburg — ³ZAE Bayern, 97074 Würzburg

The charge carrier distribution in organic thin film devices is essential for optimizing their operation characteristics. Recently, it has been shown that these current densities can be determined by means of photoluminescence (PL) studies on single guest dye molecules. [Nothaft M. et al., ChemPhysChem 12, 2590–2595 (2011)] Here, this concept is applied to common Alq₃/α-NPD OLEDs by utilizing molecular dopant ensembles in combination with µ-PL. Tetraphenyldibenzoperiflanthene (DBP) is intentionally embedded as dopant (0.1 v-%) via co-evaporation at defined positions within the Alq₃ emission layer. Upon charge injection an effective reduction in the DBP PL is observed which can be attributed to electron - exciton interaction. The macroscopic current density related to the respective PL reduction scales with the distance from the injecting electrode in qualitative agreement with a SCLC model. The validity of this model and thus, variations in vertical charge carrier distribution are studied as a function of current density as well as of temperature. Since at reverse bias PL quenching of DBP near the Alq₃/α-NPD interface is observed, a comparative study of the interfacial charge density is performed by means of integral impedance spectroscopy. [Brütting W. et al., Org. Electron., 2, 1-36 (2001)]