C_1-Symmetric [Ir(C∧N1)(C∧N~2)(O∧O)]-Tris-Heteroleptic Iridium(Ⅲ)-Complexes with the Preferentially Horizontal Orientation for High-Performance Near-Infrared Organic Light-Emitting Diodes

摘要

The development of high-efficiency near-infrared (NIR)-emitting Ir(III)-complex-based phosphors for reliable NIR-OLEDs (near-infrared organic light-emitting diodes) is still a formidable challenge. Herein, a molecule-engineered approach is developed to afford three C-1-symmetric [Ir(C^N-1)(C^N-2)(O^O)]-tris-heteroleptic Ir(III)-complexes ([Ir(iqbt)(dFppy)(acac)] (1), [Ir(iqbt)(ppy)(acac)] (2), and [Ir(iqbt)(dpqx)(acac)] (3)), whose good NIR-luminescent efficiency (phi(PL) = 0.18 for 1 (lambda(em) = 703 nm), 0.26 for 2 (lambda(em) = 715 nm) or 0.28 for 3 (lambda(em) = 707 nm)) originates from the strengthened (MLCT)-M-3 contribution (MLCT = metal-to-ligand charge transfer). Moreover, the quantitative molecular orientation determination of their doped emitting layers (EMLs) reveals that the preferentially horizontal orientation of the emitting dipoles is beneficial to their highly efficient NIR-OLEDs with light out-coupling. Especially for the NIR-OLED -2 with lambda(em) = 715 nm, a high performance (eta(Max)(EQE) = 5.30% and negligible (2%) efficiency-roll-off) is realized among the reported solution-processed NIR-OLEDs based on Ir(III)-complexes at similar color gamut. This result shows that C-1-symmetric [Ir(C^N-1)(C^N-2)(O^O)]-tris-heteroleptic Ir(III)-complexes can provide a new platform to low-cost and large-area scalable NIR-OLEDs.