| Near-infrared organic/polymer light-emitting diodes（NIR-OLEDs/PLEDs）with both high NIR-emitting quantum efficiency and significantly weak efficiency-roll-off have attracted much attention.Within the reported materials,the development of NIR-emitting iridium（III）complexeswithmononuclear[Ir（C^N）2（N^O）]-andbinuclear[（C^N）2-Ir（N^O）2-Ir（C^N）2]-heteroleptic configurations capable of adjusting to wavelength and quantum yield especially affected from the electronic effect of the N^O-ancillary ligands is not explored,to the best of our knowledge.Herein,using the nitrogen heterocyclic ligand as the HC^N main ligand,series of novel NIR-luminescent [Ir（C^N）2（N^O）]-configuredmononucleariridium-complexesand[（C^N）2-Ir（N^O）2-Ir（C^N）2]-configuredbinucleariridium-complexesbasedonthe introduction of the single/double N^O Schiff-base ligand with different electronic groups as the ancillary ligand,were designed,respectively.Especially,the electronic effect of N^O-ancillary ligand on the band gap and the radiation transition and non-radiative transition for desirable NIR luminescence was explored for the first time.Moreover,through the doping of the NIR-emitting iridium-complexes into PVK,series of NIR-PLEDs were successfully fabricated.The specific content is as follows:First,with the regid Hiqbt （1-（benzo[b]thiophen-2-yl）isoquinoline） was as the HC^N main ligand and one of the four aniline salicylaldehyde derivatives（salicylaldehyde,o-vanillin,5-bromo-2-hydroxy-3-methoxy-benzaldehydeor3,5-di-tert-butyl-2-hydroxy-benzaldehyde） as the single N^O Schiff-bases HLn（n=1-4） ancillary ligand,four nevel NIR-emitting (λem=708 nm) mononuclear iridium-complexes [Ir（iqbt）2（Ln）]（n=1-4,1-4） with the [Ir（C^N）2（N^O）]-heteroleptic configuration were obtained,respectively.The photophysical results show that the electronic effect of different ancillary ligands has little influence on the band gap of the iridium-complex.However,it does effectively lead to the specific NIR luminescence with different radiation and non-radiative transition rates.For [Ir（iqbt）2（L1）]（1）,the phosphorescence lifetime τ is 1.38 μs and the quantum yield Φemm is 0.15;For [Ir（iqbt）2（L2）]（2）,the phosphorescence lifetime τ is 1.50 μs and the quantum yield Φemm is 0.10;For complex [Ir（iqbt）2（L3）]（3）,the phosphorescence lifetime τ is 1.30μs and the quantum yield Φemm is 0.12 and for[Ir（iqbt）2（L4）]（4）,the phosphorescence lifetime τ is 1.46 μs and the quantum yield Φemm is 0.11,respectively.Secondly,through the molecular design of the series of double N^O Schiff-base H2Ln（n=5-8）ancillary ligands of four benzidine salicylaldehyde derivatives（salicylaldehyde,o-vanillin,5-bromo-2-hydroxy-3-methoxy-benzaldehydeor3,5-di-tert-butyl-2-hydroxy-benzaldehyde）,seriesofbinucleariridium-complexes[（iqbt）2Ir-（Ln）-Ir（iqbt）2]（n=5-8,5-8）characteristic of[（C^N）2-Ir（N^O）2Ir-（C^N）2]configuration were also developed.Similarly,their typical NIR-luminescence fixed at λem=708 nm does not result from the detailed electronic effect of of different double N^O Schiff base H2Ln（n=5-8） ancillary ligands.Nonetheless,the detailed NIR-emitting lifetime and quantum yield are much relative to that electronic effect,from which,[（iqbt）2Ir-（L5）-Ir（iqbt）2]（5）:τ=1.50 μs and Φem=0.10;[（iqbt）2Ir-（L6）-Ir（iqbt）2]（6）:τ=1.59 μs and Φem=0.05;[（iqbt）2Ir-（L7）-Ir（iqbt）2]（7）:τ=1.42 μs and Φem=0.07 and[（iqbt）2Ir-（L8）-Ir（iqbt）2]（8）: =1.57 μs and Φem=0.08) are exhibited,respectively.Finally,using the doping of the mononuclear iridium-complexes [Ir（iqbt）2（Ln）]（1-4）or the binuclear iridium complexes[（iqbt）2Ir-（Ln）-Ir（iqbt）2] into PVK,the solution-processed NIR-PLEDs-Ⅰ and NIR-PLEDs-Ⅱ devices were fabricated,respectively.Among the realization of NIR electroluminescence,the NIR-PLED-I-1 device further optimized with the electron-transport promotion of TmPyPB（1,3,5-tri[（3-pyridyl）-phen-3-yl]benzene）,can give rise to a superior performance of both ηmaxEQEQE up to 1.81% and almost negligible efficiency-roll-off（<2%）. |
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