Phenylpyridine and carbazole based host materials for highly efficient blue TADF OLEDs

Abstract

In this work, two host materials for blue TADF (thermally activated delayed fluorescence) OLEDs (organic light-emitting diodes) were designed and synthesized for improving the lifetime by incorporating pyridine core carbazole connected at different liking positions. These materials exhibit good thermal stability, high bond dissociation energy (BDE), and longer lifetime than the reference host. In particular, a blue TADF OLEDs system consisting of 4N-oCBP (9-(3-(2-(9 H -carbazol-9-yl)phenyl)pyridin-4-yl)-9 H -carbazole host and TCz-Trz (2,4,6-tris(2-(9 H -carbazol-9-yl)phenyl)-1,3,5-triazine) dopant exhibited the best device performances with a maximum external quantum efficiency (EQE) of 16.2% and an improvement of 88% in operational lifetime (initial luminance of 200 cd/m 2 ). This improved lifetime could be explained by the C–N BDE in the host molecular structure. The carbazole-based host molecule with different linking positions to the pyridine core developed in this study has considerable potential for improving the efficiency and lifetime of the TADF OLEDs device. • Two host materials for blue TADF OLEDs were designed and synthesized for improving the lifetime by incorporating pyridine core carbazole connected at different liking positions. • This improved lifetime could be explained by the C–N BDE in the host molecular structure.