Saturated Red Electrophosphorescence From Novel Pyridinopyridazine-Based Iridium Complexes

Abstract

Two isomeric homoleptic Ir(III) complexes with pyridinopyridazine derivative ligands were prepared first. Due to its stronger intramolecular hydrogen bonding and intermolecular interactions, complex IrPPM has a higher decomposition temperature (5% weight loss) of 387°C than IrPPP (354°C). They have similar UV–Vis absorption and photoluminescence spectra in CH₂Cl₂ solution with photoluminescence peaks around 635–636 nm. However, the emission peak of IrPPM in neat powder obviously red-shifted to 652 nm, and that of IrPPP blue-shifted to 626 nm. Simultaneously, complex IrPPM has a lower photoluminescence quantum yield of 0.3 than IrPPP (0.5). Efficient saturated red OLED devices are developed with Commission Internationale de L'Eclairage color coordinates of (0.67, 0.32) and (0.66, 0.32), respectively. The maximum external quantum efficiencies of both devices exceed 11%. These results demonstrate the great potential of pyridinopyridazine derivatives for developing new iridium complexes for OLED applications.