Methoxyl modification in furo[3,2-c]pyridine-based iridium complexes towards highly efficient green- and orange-emitting electrophosphorescent devices†
Abstract
Two new furo[3,2-c]pyridine-based Ir complexes, namely (4-MeOpfupy)2Ir(acac) and (3-MeOpfupy)2Ir(acac), were designed and synthesized by introducing a methoxyl group into the 4- and 3-positions of the phenyl ring on the C^N ligand. It was found that the position of the methoxyl group has an important influence on the electrochemical and photophysical properties, as well as electrophosphorescent device performance. Compared with the reference complex (pfupy)2Ir(acac) without any methoxyl group (538 nm), (4-MeOpfupy)2Ir(acac) with a methoxyl group at the 4-position shows a blue-shifted emission peak at 523 nm originating from the methoxyl-induced enhancement of the LUMO level, whereas (3-MeOpfupy)2Ir(acac) with a methoxyl group at the 3-position shows a red-shifted emission peak at 602 nm originating from the methoxyl-induced enhancement of the HOMO level. The corresponding PhOLEDs based on (4-MeOpfupy)2Ir(acac) and (3-MeOpfupy)2Ir(acac) realize highly efficient green and orange electroluminescence with CIE coordinates of (0.37, 0.60) and (0.60, 0.40), revealing a state-of-the-art EQE as high as 29.5% (100.7 cd A−1) and 16.7% (43.9 cd A−1), respectively. These impressive results indicate that methoxyl modification is a valid way to tune the molecular energy levels and emissive color for Ir complexes while not obviously sacrificing the final device performance.
- This article is part of the themed collection: 2017 Journal of Materials Chemistry C HOT Papers