1,5‐Diazocine‐Based Diaryl Ketones: Design, Synthesis, and Optoelectronic Properties

ABSTRACT Three novel heterocyclic host based on diaryl ketone‐tethered 1,5‐diazocines were designed and synthesized for applications in phosphorescent organic light‐emitting diodes (PhOLEDs). The hosts were derived by anchoring the naphthyl ketone (TBN), anthryl ketone (TBA), and phenanthryl ketone (TBP) to the 1,5‐diazocine core. The materials were successfully characterized using spectroscopic techniques. TBN and TBP exhibited low external quantum efficiency of 1.5% and 1.9% when explored as hosts in PhOLED devices. Among the series, TBP exhibited the highest luminance of 4160 cd/m 2 , maximum luminance efficiency of 6.3 cd/A, and power efficiency of 3.21 lm/w, when doped with Ir(ppy) 3 in PhOLED. Nevertheless to our surprise, TBA manifested the lowest device performance than other TBs as a host due to low carrier mobility caused by a highly twisted structure as deciphered from the comparative analysis of single‐crystal structure that could impede carrier transport crucial for efficient electroluminescence. The outcomes of electroluminescence were validated and explained with analysis of single‐crystal structure, and also with the aid of density functional theory.