Department of Applied Chemistry, Providence University, Taichung, 43301, Taiwan.
Institute of Lighting and Energy Photonics, National Chiao Tung University, Tainan, 71150, Taiwan.
Chemistry. 2019 Apr 11;25(21):5489-5497. doi: 10.1002/chem.201805902. Epub 2019 Mar 19.
Solid-state near-infrared (NIR) light-emitting devices have recently received considerable attention as NIR light sources that can penetrate deep into human tissue and are suitable for bioimaging and labeling. In addition, solid-state NIR light-emitting electrochemical cells (LECs) have shown several promising advantages over NIR organic light-emitting devices (OLEDs). However, among the reported NIR LECs based on ionic transition-metal complexes (iTMCs), there is currently no iridium-based LEC that displays NIR electroluminescence (EL) peaks near to or above 800 nm. In this report we demonstrate a simple method for adjusting the energy gap between the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) of iridium-based iTMCs to generate NIR emission. We describe a series of novel ionic iridium complexes with very small energy gaps, namely NIR1-NIR6, in which 2,3-diphenylbenzo[g]quinoxaline moieties mainly take charge of the HOMO energy levels and 2,2'-biquinoline, 2-(quinolin-2-yl)quinazoline, and 2,2'-bibenzo[d]thiazole moieties mainly control the LUMO energy levels. All the complexes exhibited NIR phosphorescence, with emission maxima up to 850 nm, and have been applied as components in LECs, showing a maximum external quantum efficiency (EQE) of 0.05 % in the EL devices. By using a host-guest emissive system, with the iridium complex RED as the host and the complex NIR3 or NIR6 as guest, the highest EQE of the LECs can be further enhanced to above 0.1 %.
近年来，固态近红外（NIR）发光器件作为能够穿透人体组织深处的 NIR 光源受到了广泛关注，适用于生物成像和标记。此外，固态 NIR 发光电化学电池（LEC）相对于 NIR 有机发光器件（OLED）显示出了多个有前景的优势。然而，在报道的基于离子过渡金属配合物（iTMCs）的 NIR LEC 中，目前还没有基于铱的 LEC 显示出近 800nm 或以上的 NIR 电致发光（EL）峰。在本报告中，我们展示了一种简单的方法，用于调整基于铱的 iTMCs 的最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）之间的能隙，以产生 NIR 发射。我们描述了一系列具有非常小能隙的新型离子铱配合物，即 NIR1-NIR6，其中 2,3-二苯基苯并[g]喹喔啉部分主要负责 HOMO 能级，而 2,2'-联喹啉、2-(喹啉-2-基)喹唑啉和 2,2'-联苯并[d]噻唑部分主要控制 LUMO 能级。所有配合物都表现出 NIR 磷光，发射峰高达 850nm，并已作为 LEC 的组件应用，在 EL 器件中显示出 0.05%的最大外量子效率（EQE）。通过使用主体-客体发射系统，以铱配合物 RED 作为主体，配合物 NIR3 或 NIR6 作为客体，可以进一步提高 LEC 的最高 EQE 超过 0.1%。
