| With the advent of the information age, the information is expanding rapidly. A huge amount of information makes enormous demands on the information storage, transmission, display and processing so on. The importance of information display technology has been widely concerned. Currently, the solid-state light-emitting electrochemical cells (LECs) is a moreadvanced display technology, compared with the traditional light-emitting diode (OLED), the different luminescence mechanism brings it many advantages: First, It owns single-layer device structure. The luminescent material itself has ion mobility, which makes the device simple and easy to prepare. Second, the air steady metal can be used as the metal electrode. Because of the formation of ohmic contact on the interface between electrode and organic layer, the injection of carriers need not jump the barrier which exists in OLED. So the device has no special requirements on the metal electrode. The air stable metal materials (such as Au, Al, Ag, etc.) all can be used as the cathode material of solid-state light-emitting electrochemical cells (LECs). Third, the device has a relatively low starting voltage. In theory, it is independent of the film thickness of organic layer, while is related to the energy gap of the complex. Fourth, the efficiency of the device is much higher. Because the carriers is injected into light-emitting materials through the electrochemical redox reaction near the interface, electron and hole injection have been balanced more easily.Solid-state light emitting electrochemical cells use mostly ionic transition metal complexes as the luminescent materials, because the strong interaction between the metal and the ligands makes the transition metal complexes with special characteristics which triplet state of a metal to ligand charge transfer (MLCT) excited state. The heavy metals atomic spin coupling in complexes, singlet and triplet mixed,and the symmetry of triplet excitons are destroyed, resultly their decay are fasted to generate higher efficiency electricity phosphorescence. Singlet state also has some triplet nature, the decay time becomes much longer. The intersystem crossing (ISC) efficiency from the singlet to triplet is increased, which issued a highly efficient phosphor. Among several common heavy metals complexes, Ir(â…¢) complexes is a hot research field in electroluminescence because of its relative short phosphorescence life and luminescence quantum efficiency.Ionic iridium complexes also have much more features than neutral iridium complexes have,that make it possible to become a better electroluminescent material. First, compared with the neutral iridium complexes, ionic iridium complexes are synthesized in a more moderate condition; Second, these complexes have the stably reversible oxidation- reduction potential, which is helpful to improve the device stability; In addition, because those complexes have the charges and counterions, it is beneficial to injection and transport of carrier, reducing device power consumption.The main content of this thesis is as follows:1. In this paper, improving the performance of light-emitting materials in order to get efficient light-emitting devices, for this purpose, we design and synthesize a number of imidazole and oxadiazole ligands. They all have a good transmission of electron, light-emitting properties and chemical stability, so are the class of electron transport materials which are the most widely applied and studied. We get complexes with imidazole and oxadiazole as ligands and coordination with iridium, [Ir(ppy)2(pbhmz)]+ (PF6-), [Ir (Podz)2(pmz)] + (PF6-), [Ir(ppy)2(pmz)]+ (PF6-)å'Œ[Ir (ppy)2(pphmz)] +(PF6-), where pmz, podz, pbhmz and pphmz are1-Phenyl-2-yl)-1H-benzoimidazole, 2,5-Diphenyl-[1,3,4] oxadiazole,1-Benzyl-2-pyridin-2-yl-1H-benzoimidazole and 2-(pyridin-2-yl)-1-(pyridin-3- ylmethyl) -1H-benzo[d]imidazole, respectively.Those complexes are characterized by single crystal structure, IR and NMR spectra.2. We study the photophysical and electrochemical properties of four complexes and discusse the nature of the excited state by photoluminescence and quantitative calculation of the complexes. We study relationship between photoluminescence and electroluminescent properties and the chemical structure of the complex.3. We study the properties of the various light-emitting electroluminescent material used in LEC devices. Constantly, though changing the complex concentration, incorporation ratio of ionic liquids , and each layer thickness, the luminance and efficiency of the LECs have been greatly improved, accessing to a high-performance electrochemical devices. |
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