Efficient NIR-OLEDs based on color-purity near-infrared (NIR) tris-/bis-heteroleptic iridium(<sc>iii</sc>) complexes with a single color-responsible ligand

Constrained by the so-called "energy gap law", the development of Ir(iii)-complex-based efficient color-purity NIR-OLEDs is highly challenging. Herein, a robust tris-/bis-heteroleptic molecular design strategy for the fabrication of tris-[Ir(dpbq)(iqbt)(pbi)] (2) and bis-[Ir(dpbq)2(pbi)] (1) is reported, where desirable color-purity NIR-emission (full emission beyond 700 nm) is determined using the Hdpbq-HC<^>N ligand, and their T1 is characteristic of 3MLCT/3LC-admixed transitions with 3ILCT being the dominant component. Notably, owing to the augmented 3MLCT and lower 3ILCT contributions, a larger efficiency (Phi PL = 4.2% (2) versus 3.4% (1)) and narrower FWHM (63 nm (2) versus 70 nm (1)) are achieved for [Ir(dpbq)(iqbt)(pbi)] (2) than those of [Ir(dpbq)2(pbi)] (1). Thus, a record high-performance (eta MaxEQE = 1.824% (lambda MaxEL = 788 nm) and weak efficiency-roll-off) and an RCMax (RC = radiance capacity) of up to 591 mW sr-1 m-2 V-1 for color-purity polymer-matrixed NIR-OLED-2 are realized. Importantly, the "compromise" effect between 3MLCT and 3LC (3ILCT-dominant) in the T1 state engenders tris-heteroleptic Ir(iii)-complexes (such as [Ir(dpbq)(iqbt)(pbi)] (2)), a platform for fabricating efficient color-purity NIR-OLEDs with practical application potential.