From Molecules to Devices: Effect of Pd-Catalyzed C–H Bond Arylation to Improve Metrics
Résumé
In this study, we detail advancements in the design and application of neutral, arylated, cyclometalated iridium(III) complexes in the use of OLEDs. We utilized the “catalysis-on-the-complex” approach to directly arylate (C^N)2Ir(acac) [where C^N represents either 2-(2,4-difluorophenyl)pyridine or 2-(2,4-difluorophenyl)-5-methoxypyridine] through Pd-catalyzed C–H bond arylation with 4-bromobenzotrifluoride. The reaction regioselectivity occurred on both cyclometalated ligands at the C–H bonds flanked by two fluorine atoms. Photophysical measurements in solution indicated that while the emission energy remained unchanged (blue colors, λmax EL = 482–490 nm), a significant enhanced quantum yield was observed for arylated complex. Impressively, devices incorporating these complexes as green-blue emitters revealed that arylation also boosts device performance metrics in terms of luminance efficiency, external quantum efficiency (EQE), and brightness. In contrast, the introduction of methoxy substituent at the meta-position of the nitrogen–iridium bond yielded modest metrics. This study illustrates the crucial role of ligand design in the rational development of blue emitters.