Homoleptic iridium complexes based on furo[3,2-c]pyridine ligand for efficient phosphorescent OLEDs

Abstract

Abstract Two novel homoleptic Ir complexes Ir(pfupy)3 and Ir(thfupy)3 have been designed and synthesized, which bear 4-phenylfuro[3,2-c]pyridine and 4-(thiophen-2-yl)furo[3,2-c]pyridine as the CˆN ligand, respectively. Because of the lower π-π* energy of thiophene than phenyl, Ir(thfupy)3 shows an obvious red-shifted emission peaked at 577 nm relative to Ir(pfupy)3 (533 nm). Moreover, the photoluminescent quantum yield (PLQY) and lifetime of Ir(pfupy)3 are determined to be 0.83 and 0.92 μs, whereas they are 0.35 and 2.09 μs for Ir(thfupy)3 due to the energy gap law and weak spin-orbital coupling. Benefiting from the good thermal stability, both Ir(pfupy)3 and Ir(thfupy)3 can be vacuum deposited without decomposition to fabricate the corresponding phosphorescent OLEDs (PhOLEDs). Maximum external quantum efficiencies as high as 26.7% (97.9 cd/A) and 15.3% (46.6 cd/A) together with Commission Internationale de l’Eclairage coordinates of (0.42, 0.57) and (0.56, 0.42) are realized for Ir(pfupy)3 and Ir(thfupy)3, respectively. The obtained promising device performance clearly indicates the great potential of homoleptic furo[3,2-c]pyridine based Ir complexes for efficient PhOLEDs.