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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 17: Poster I

CPP 17.8: Poster

Montag, 9. März 2026, 19:00–21:00, P5

Thin Films of Substituted Imidazoquinolines as Emitters for Blue OLED Devices — •Lasse Freitag¹, Pascal Schweitzer¹, Carina Rössiger², Thomas Oel², Richard Göttlich², and Derck Schlettwein¹ — ¹Justus-Liebig-Universität Gießen, Institut für Angewandte Physik, Heinrich-Buff-Ring 16, D-35392 Gießen — ²Justus-Liebig-Universität Gießen, Institut für Organische Chemie, Heinrich-Buff-Ring 17, D-35392 Gießen

Organic semiconductors are routinely applied in microelectronics. Still challenging is the field of organic blue light emitting diodes (OLED), due to degradation of the emitters. We study the application of imidazoquinolines such as 4EstPhPh(iso)IC as emitters. Different substitutional patterns allow for tuning of their opto-electronic properties. We achieved thin films of 4EstPhPh(iso)IC via physical vapor deposition (PVD). Promising blue photo- and electroluminescence was found in solid state. Film formation at interfaces with contact materials was studied by in-situ Kelvin-probe force microscopy (KPFM). On the p-conducting poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) we found a Stranski-Krastanov (SK) growth of the emitter. X-ray diffraction (GI-XRD) confirmed a crystalline structure in these films, in line with single crystal data. Further, the growth of n-conducting bathocuproine (BCP) on the emitter layer was monitored by KPFM, revealing SK growth followed by formation of 3D crystalline islands. As a fundamental prerequisite, morphological stability at air was confirmed by microscopy. Therefore, we built OLED with varying thickness to find the best-performing layer stack.

Keywords: organic semiconductor; organic light emitting diode (OLED); Kelvin-Probe Force Microscopy (KPFM); thin film; photoluminescence (PL)