| Recently, with the development of the optical communication, sensors, realtime biological monitoring in vivo and medical imaging, near-infrared (NIR) materials have played a much important role in military, energy and medical treatment. Among these NIR materials, the NIR light-emitting materials (LEMs) have become one of the most dynamic and vital forefront researches owing to their low cost and easily adjusted function and structures. The research advances in NIR organic electroluminescent materials (OELMs) were reviewed in this dissertation. For the series of problems, such as few types and low efficiency for the NIR-OELMs, a series of NIR-OELMs based on cyclometalated platinum and iridium complexes have been designed and synthesized with donor (D) and acceptor (A) units. Their opto-physical, electro-chemical, thermal properties and morphology were also studied by UV-Vis absorption, photoluminescence (PL), cyclic voltammetry (CV), thermogravimetic analysis (TGA) and atomic force microscope (AFM), respectively. Used these cyclometalated platinum (II) and iridium (III) complexes as dopant, the single-dopant single-emissive-layer (SEL) polymer light-emitting devices (PLEDs) were made. Their electrolumine-scent (EL) properties and structure-property relationship were studied. The key studies results in this dissertation are listed below:1. Two kinds of novel D-A-A’-based cyclometalated ligands and their NIR-emitting cyclometalated platinum (II) complexes of (n-C8H17OTPA-BT-Q)Ptpic,(i-C8H17-Cz-BT-Q)Ptpic,(MeOTPA-BT-Q)Ptpic,(MeOTPA-BT-Iq)Ptpic and (MeOTPA-BT-Iq)PtpicTPAOMe were designed and synthesized, in which alkyl triphenyl amine (n-C8H17OTPA and MeOTPA) and carbazole (i-C8H17Cz) units are donor (D) units, benzothiadiazolec (BT) is the first acceptor (A) unit, quinoline (Q) and isoquinoline (Iq) are the second acceptor (A’) unit. Picolinic acid (pic) and triphenylamine-functionalized picolinic acid (MeOTPApic) are auxiliary ligands. Using these cyclometalated platinum (II) complexes as a single dopant, the SEL PLEDs exhibited a NIR emission peaked at760nm or725nm. The maximum external quantum efficiency of0.12%and the maximum radiance intensity of112μW cm-2at11.7mA cm-2were obtained in the (TPA-BT-Q)Ptpic-based device at doping concentrations of2.0wt%.2. Another novel class of the D-A-A’-based cyclometalated ligands and their NIR-emitting cyclometalated platinum (II)/iridium (III) complexes of (MeO- TPA-BTA-Iq)Ptpic and (MeOTPA-BTA-Iq)2Irpic was designed and synthesiz-ed, in which methoxyl triphenylamine (MeOTPA) unit is a D unit, benzotri-azole(BTA) is the A unit, and isoquinoline (Iq) is the A’ unit. Using these cyclo-metalated platinum (II)/iridium (III) complexes as a single dopant, the SEL PLEDs exhibited a NIR emission peaked at766nm. The maximum brightness of765cd m-2and the maximum current efficiency of0.16cd A-1were observed in the (MeOTPA-BTA-Iq)Ptpic-based device at doping concentrations of1.0wt%.3. A novel class of the D-A-A’-based cyclometalated ligands and their NIR-emitting dinuclear cyclometalated platinum (II) complexes of (C8H17OTPA-BT-Q)2Pt2-(pic)2BDT and (MeOTPA-BT-Q)Pt2(pic)2Flu were obtained, in which alkyl triphenylamine (C8H17OTPA and MeOTPA) units are the D units, BT is the A unit, Q and Iq are the A’ units, bipicolinic acid derivatives are the bridged (B) unit. BDT(pic)2and Flu (pic)2are the bipicolinic acid derivatives of benzo[1,2-b:4,5-b’] dithiophene (BDT) and fluorene (Flu), respectively, which have large planar conjugated properties and high fluorescence quantum efficiency. This kind of dinuclear cyclometalated platinum (II) complexes exhibited NIR emission with a maximum emission peak at721nm.Two novel classes of organic cyclometalated platinum (II) and iridium (III) com-plexes have been developed used as NIR-OELMs in this dissertation. The basic relationship between molecular structure and NIR emission has been revealed. It’s significantly theoretical reference value for promoting development of organic NIR materials and their devices. |
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