Designing a Deep Blue Emitter by Disrupting Phenanthroimidazole Conjugation for Non-Doped OLEDs with an External Quantum Efficiency > 13.

The pursuit of highly efficient non-doped organic light-emitting diodes (OLEDs) has promoted the development of blue emitters with a design strategy. In this study, we developed a deep blue emitter featuring hybridized local and charge-transfer characteristics. The blue emitter, PIMAnCz, consists of a molecular framework of a disrupted phenanthroimidazole moiety, which resulted in large steric hindrance and reduced electron delocalization along the fragments. These features lead to a high spin-orbit coupling between the high-lying triplet level and low-lying singlet level (S1) and a photoluminescence of 59%. More importantly, the non-doped device employing a neat PIMAnCz emitting layer delivered a maximum external quantum efficiency of 13.19% with Commission Internationale de l'Eclairage (CIE) coordinates of (0.15, 0.09), placing it among the highest efficiencies attained for a non-doped deep blue OLED with CIEy < 0.10. These findings provide practical design insights for a highly efficient blue emitter for non-doped deep blue OLED applications.