C₁‐Symmetric [Ir(C^N¹)(C^N²)(O^O)]‐Tris‐Heteroleptic Iridium(III)‐Complexes with the Preferentially Horizontal Orientation for High‐Performance Near‐Infrared Organic Light‐Emitting Diodes

Abstract

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 C1‐symmetric [Ir(C^N1)(C^N2)(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 (ΦPL = 0.18 for 1 (λem = 703 nm), 0.26 for 2 (λem = 715 nm) or 0.28 for 3 (λem = 707 nm)) originates from the strengthened 3MLCT 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 λem = 715 nm, a high performance (ηEQEMax = 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 C1‐symmetric [Ir(C^N1)(C^N2)(O^O)]‐tris‐heteroleptic Ir(III)‐complexes can provide a new platform to low‐cost and large‐area scalable NIR‐OLEDs.

Asymmetric Tris-Heteroleptic Cyclometalated Phosphorescent Iridium(III) Complexes: An Emerging Class of Metallophosphors

“…Thanks to the preferential horizontal orientation of the emitting dipoles, a high-performance NIR electroluminescence based on 28 (λ EL = 715 nm, EQE max = 5.3%) was achieved with negligible efficiency roll-off (<2%) by the solution-processing method (Figure 6b,c). 44 Because of the presence of the asymmetric 3-hydroxypicolinic acid ligand, a pair of stereoisomers 30 and 31 were generated and confirmed by their crystal structures (Figure 6). 45 Two complexes share almost the same emission wavelength (697 nm for 30, 696 nm for 31) with similar emissive lifetimes (0.33 μs for 30, 0.38 μs for 31) but slightly different PLQYs (0.27 for 30, 0.33 for 31).…”

Approaching the Shortest Intermetallic Distance of Half‐Lantern Diplatinum(II) Complexes for Efficient and Stable Deep‐Red Organic Light‐Emitting Diodes

“…[16][17][18][19][20][21][22] As a result, the external quantum efficiencies (EQEs) of deep red OLEDs doped with either a phosphorescent or a TADF emitter have been reported to be < 20% when the electroluminescence maximum (𝜆 EL ) is longer than 650 nm. [23][24][25][26][27][28][29][30][31] On the other hand, operational stability of the deep red and near infrared (NIR) OLEDs have only been scarcely reported, [6,31] among which notable progresses were made by Kido et al who investigated the role of host molecules in the device stability. [23,28,30] From the excited state dynamics perspective, it is pivotal to simultaneously increase the radiative decay rate and reduce the nonradiative decay rate for attaining high-performance deep red OLEDs featuring high efficiencies, low roll-offs, and long operational lifetimes.…”

Divinylanthracene-Containing Tetracationic Organic Cyclophane with Near-Infrared Photoluminescence

“…These properties render this class of fluorophores appealing candidates for various biological applications, such as biomolecular sensing, bioimaging, and theranostics . In addition to these biomedical applications, NIR-emissive molecules can be incorporated into high-performance, organic light-emitting diodes (OLEDs) and in the generation of photonic devices.…”