3-Phenylisoquinoline Ligand-Driven Enhanced Triplet Emission in an Ir(III) Phosphor Enabling High-Efficiency in Orange and Hybrid White OLEDs

Abstract We report the synthesis, photophysical properties, and electroluminescent performance of a Ir(3-phenylisoquinoline)3 (Ir(3-piq)3) complex. Single-crystal X-ray analysis reveals a distorted octahedral geometry with strong intermolecular interactions that enforce rigid molecular packing and abate nonradiative decay by reducing structural reorganization. Photophysical investigations reveal weak orange emission in solution and significantly enhanced emission in doped films. Optimized organic light-emitting diodes (OLEDs) achieve a low turn-on voltage of 2.5 V, a maximum external quantum efficiency (EQEmax) of 22.8%, and a brightness of 49616 cd/m2 with stable electroluminescence. Moreover, hybrid white OLEDs were fabricated by incorporating the blue TADF emitter, 3DPy-pDTC as an auxiliary dopant. The fabricated devices exhibit warm-white emission at 0.7 wt % doping of Ir(3-piq)3, delivering EQEmax of 17.7%. Notably, reducing the doping concentration of Ir(3-piq)3 to 0.5 wt % results in a well-balanced bright white emission with CIE co-ordinate of (0.29, 0.33) and achieves an EQEmax of 14.7%. These performances are attributed to efficient exciton utilization driven by synergistic phosphorescence and rapid reverse intersystem crossing in TADF emitters. Overall, this work demonstrates an effective strategy for achieving high-efficiency and stable orange emission in Ir-complexes and color-tunable hybrid white OLEDs through synergistic exciton management.