Saturated-blue-emitting [3+2+1] coordinated iridium(iii) complexes for vacuum-deposited organic light-emitting devices

Abstract

A new class of deep-blue phosphorescent [3+2+1] coordinated iridium(III) complexes containing phenyl-3H-imidazo[4,5-b] pyridine-based (C^C) bidentate ligands have been synthesized, characterized, and applied as phosphorescent dopants in the fabrication of vacuum-deposited organic light-emitting devices (OLEDs). The manipulation of the relative bulkiness of the C^C ligands is the key to control the emission energies in solid-state thin films, ranging from 415 to 470 nm. Taking advantages of the intra-ligand charge transfer nature of the emissive state, these complexes display short excited-state lifetimes in the sub-nanosecond regime of 0.3 to 1.1 μs, yielding high radiative decay rate constants on the order of up to 10⁶ s⁻¹. High-performance vacuum-deposited deep-blue-emitting OLEDs have been fabricated based on these complexes, demonstrating an external quantum efficiency (EQE) of 11.2% and Commission International de L’Eclairage (CIE (x,y)) coordinates of (0.16, 0.07), making them the deepest blue emitters for this class of new [3+2+1] Ir phosphorescent materials.