Molecular Engineering of Phenylbenzimidazole-Based Orange Ir(III) Phosphors toward High-Performance White OLEDs.
To develop B-O complementary-color white organic light-emitting diodes (WOLEDs) exhibiting high efficiency and low roll-off as well as color stability simultaneously, we have designed two orange iridium(III) complexes by simply controlling the position of the methoxyl group on the cyclometalated ligand. The obtained emitters mOMe-Ir-BQ and pOMe-Ir-BQ show good photophysical and electrochemical stabilities with a broadened full width at half-maximum close to 100 nm. The corresponding devices realize highly efficient electrophosphorescence with a maximum current efficiency (CE) and power efficiency (PE) of 24.4 cd A-1 and 15.3 lm W-1 at a high doping concentration of 15 wt %. Furthermore, the complementary-color all-phosphor WOLEDs based on these phosphors exhibit good performance with a maximum CE of 31.8 cd A-1, PE of 25.0 lm W-1, and external quantum efficiency of 15.5%. Particularly, the efficiency of this device is still as high as 29.3 cd A-1 and 14.2% at the practical brightness level of 1000 cd m-2, giving a small roll-off. Meanwhile, extremely high color stability is achieved by these devices with insignificant chromaticity variation.