Design And Synthesis Of Novel Ionic Iridium Complexes And The Application In The Light-emitting Electrochemical Cell

Nowdays, organic light emitting diodes(OLEDs) are planing increasingly important role in the acquisition of knowledge and improvement quality of life for people,They have Has great potential and broad prospects for business,However, light-emitting electrochemical cells(LECs) are an important branchs of OLEDs.Recently dramatic advances have been achieved in the field of LECs, which are being developed for display and lighting applications. Ionic transition metal complexes (iTMCs) offer an alternative to such processing associated with conventional OLEDs.Their excellent stability in multiple redox states implies that electronic charges can be readily injected and transported. Furthermore, iTMCs such as [Ru(bpy)₃]²⁺(PF₆^-)2 are ionically conducting as the PF₆^- counterions can redistribute under an applied bias. This action creates an ionic space charge near each electrode (excess PF₆^- at the anode and uncompensated [Ru(bpy)₃]²⁺ at the cathode), which serves to assist electronic charge injection, even to the point of efficiently injecting electrons from air-stable metals. In this manner, these devices are similar to the socalled light-emitting electrochemical cells (LECs), which are fabricated by dispersing salts into organic semiconductors. Additionally, the luminescence efficiency of iTMCs can be extremely high, with photoluminescence quantum yields approaching 100%, as emission from these materials arises almost exclusively from triplet states. As for processing, iTMCs can generally be spin cast directly from solution. These properties indicate that efficient electroluminescent devices can be fabricated from single-layer iTMC devices.Charged iridium(Ir) complexes have many other features except for high quantum efficiencies and easily tunable emission wavelength that may make them one of the finest candidates for lightings, displays and light-emitting electrochemical cells (LECs). First, the synthesis condition of charged Ir complexes is much milder than that of neutral ones. Second, inert metal electrodes resistant to oxidation in air, such as Au and Pt, can be used in efficient devices based on charged Ir complexes. Third, further improving the stability of devices can be expected due to their excellent redox stabilities. In addition, charged Ir complexes are endorsed with the properties of charge transfer, consequently lowering power consumptions of devices. However, for the blend system of charged Ir complexes into hydrophobic host materials, the problem of phase separation is more serious them that of neutral Ir complexes due to the poor compatibility. And this problem is an obstacle to their applications in organic electronics. In order to solve this problem, modify the structure of ligands should to be done, and design, synthesize novel ionic iridium(Ir) complexes of high luminous efficiency to arrive LEC of high luminescence, high efficiency, This dissertation is comprised of the follow two parts:1,Two novel ligands (mptop and ptop) contain 1,3,4--oxadiazole and pyridine were designed and synthesized, and two ionic iridium(Ir) complexes [Ir(mptop)(ppy)₂]⁺(PF₆^-)and [Ir(ptop)(ppy)₂]⁺(PF₆^-) were prepared, where mptop is 2-(5-p-Tolyl-[1,3,4]oxadiazol-2-yl)- pyridine, ptop is 2-(5-Phenyl-[1,3,4]oxadiazol-2-yl)-pyridine, Compounds containing 1,3,4-oxadiazole(OXA) which possess excellent electron affinity, good light-emitting, thermal stability, and chemical stability characteristic, are commonly used as electron transporting and hole blocking materials in OLEDs. All of the complexes were characterized by IR, 1HNMR and X-Ray diffraction. Initiative study showed that the complexes were expected to be a good candidate for lighting and display application.2,Photophysical and electrochemical properties of these complexes were investigated, By study the UV-visible absorption spectrum, fluorescence emission spectrum and theoretical calculations of the complexes, we received that complexes with different ligands showed different optoelectronic properties and all complexes exhibited intense and long-live emission, clarified that the relationship between chemical structure and complexes,properties in photophysics and electrochemistry.3.We fabricated organic red light-emitting electrochemical cells (LECs) based on the two complexes [Ir(mptop)(ppy)₂]⁺(PF₆^-) and [Ir(ptop)(ppy)₂]⁺(PF₆^-) respectively. from devices, start-up voltage, response time, maximum brightness, luminous efficiency and device life, we studied the molecular structure of the complex changes in the impact on device performance.