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

Abstract

In sharp contrast to low-efficiency and/or considerable (more or less) visible-light remnant in the NIR-emissive protocols of most Ir(III)-complex-based NIR-OLEDs, the development of efficient color-purity ones is difficult and greatly challenging by the so-called “energy gap law”. Herein, a robust tris-/bis-heteroleptic molecular design strategyto tris-[Ir(dpbq)(iqbt)(pbi)] (2) versusbis-[Ir(dpbq)2(pbi)] (1) is founded, where desirable color-purity NIR-emission (full-emission beyond 700 nm) is determined by the Hdpbq-HC^N ligand within, and their T1 is characteristic of 3MLCT/3LC-admixed transitions with 3ILCT-dominant. Noticeably, owing the augmented 3MLCT while less 3ILCT contributions, the larger efficiency (ΦPL = 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(dppq)2(pbi)] (1), respectively, and thus, its record high-performance (ηEQEMax = 1.824% (λELMax = 788 nm) and weak efficiency-roll-off) and the RCMax (RC = radiance capacity) up to 591 mW/(sr⋅m2⋅V) color-purity polymer-matrixed NIR-OLED-2 is realized. Importantly, the “compromise” effect between 3MLCT and 3LC (3ILCT-dominant) in T1 state, engenders tris-heteroleptic Ir(III)-complexes (like [Ir(dpbq)(iqbt)(pbi)] (2)) a platform to efficient color-purity NIR-OLEDs with practical potentials.