Star-Shaped Phenanthroimidazole-Triphenylamine-Based Yellow Organic Emitter for Organic Light Emitting Diodes

Abstract

In this work, new star-shaped conjugated organic emitter, namely tris(4-(1-(9,9-diethyl-9H-fluoren-2-yl)-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)amine (PIFTPA) with donor-?-acceptor (D-?-A) structure, was designed and synthesized by combining three fluoren-phenanthroimidazole arms into a triphenylamine core and characterized using 1H, 13C NMR and mass spectrometry. The detailed photophysical, thermal, electrochemical and electroluminescence properties were systematically studied. The organic emitter exhibits high glass transition temperature (230 C) and high thermal stability with decomposition temperature. Electrochemical analysis reveals that the emitter has distinct oxidation and reduction behaviours. Furthermore, theoretical calculations (DFT) were performed to get a better understanding of the electronic structure. The OLEDs using this emitter as emissive material showed good device performance (6.45 cd/A, 4.39 lm/W, and 3.01%) with yellow emission and a low turn-on voltage (2.87 V). The results demonstrate that TPA integrated with phenthroimdazole plays an important role in the device performance. 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim