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

Abstract

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 (Φ_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 (η^Max_EQE = 1.824% (λ^Max_EL = 788 nm) and weak efficiency-roll-off) and an RC^Max (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.