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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 28: Poster III

CPP 28.8: Poster

Wednesday, March 20, 2024, 11:30–13:30, Poster C

Electroluminescence and Charge Transport Barriers in Blue OLED Based on Thin Films of 3 Phenyl-1-(quinoline-2-yl)imidazo[1,5-a]quinoline — •Pascal Schweitzer¹, Carina Rössiger², Alper Yilmaz¹, Gustav Nolte¹, Marius Eckert¹, Richard Göttlich², and Derck Schlettwein¹ — ¹Institut für Angewandte Physik, Justus-Liebig-Universität Gießen — ²Institut für Organische Chemie, Justus-Liebig-Universität Gießen

3-Phenyl-1-(quinoline-2-yl)-imidazo-[1,5-a]-quinoline (PhCIC) is a promising organic emitter molecule for the possible application in blue organic light-emitting diodes (OLEDs). We prepared thin films by physical vapor deposition and studied their photoluminescence (PL) and electroluminescence (EL) to evaluate PhCIC as emitter. Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) served as back contact, poly(9-vinylcarbazole) (PVK) as hole injector, and bathocuproine (BCP) as electron injector contacted by Al. Emission by PVK in the same spectral range as that of PhCIC hindered a detailed discussion. This problem was solved by omitting PVK and the measured EL of PhCIC was in good agreement with PL of PhCIC in solution or as a thin film. To identify the contact responsible for the quite high onset voltage of 10-15 V that we found, film growth and electrical contact formation of PhCIC to PEDOT:PSS and BCP were studied in situ by Kelvin probe force microscopy (KPFM). We conclude that charge injection barriers significantly contribute to the onset voltage and possible steps to tune the alignment of transport levels will be discussed.

Keywords: organic light emitting diode; luminescence; Kelvin probe force microscopy; contact formation