Synthesis And Physical Properties Of Schiff Base Zinc Complexes As Organic Electroluminescent Materials

Organic light-emitting devices(OLEDs) is not only a great point of newflat panel displays, but also one of the first choices of green lighting sourceof the 21 century, during to their merits such as low drive voltage, highbrightness, wide visual angle, quick response, and simple fabricationtechnics. As the present time, low power-conversion efficiency, short usefullife and bad long-term stability are the critical problems to block the utilityand marketization of OLEDs. However, exploiting organic light-emittingmaterials with high efficiency and stable physical characteristics, choosingappropriate electrode materials, searching for new film fabrication technics,and optimizing device configuration, improving the efficiency and usefullife of device are the primary aims of study work.In this paper, two kinds of Schiff base Zinc organic complexes asorganic electroluminescent materials were mainly synthesized. Theirphysical properties in relation to organic electroluminescence were investigated in detail. The developments were obtained in the designs ofnovel materials and device structures and the studies of materialstructure/optical and electrical properties relationships.1. Two kinds of Schiff base organic metal complexes, Bis(salicyl-idene)-1, 2-phenylenediamine Zinc(Zn(salph)) and Bis(salicylidene)-1,6-hexanedia-mine Zinc(Zn(salhex)) with high purity, were synthesized byliquid-phase reaction and purified by vacuum sublimation, molecularstructures were confirmed by element analysis, ¹H NMR spectra and FT-IRspectra; their thermal stabilities were characterized by TG-DTA curves;phase structures were analyzed by X-ray diffraction(XRD); theirmicrostructures were identified by scanning electron microscope(SEM).Experimental results showed that:â‘ . Zn(salph) is a clubbed polycrystallinematerial, with glass temperature and decomposition temperature being183℃and 449℃, respectively;â‘¡. Zn(salhex) is a sheet polycrystallinematerial, with preliminary decomposition temperature being 325℃.2. Zn(salph) and Zn(salhex)'s luminescent properties were studied byUV absorption spectra and fluorescence spectra, In addition, the structuresof energy band, photophysical and photochemical of those were studied bycyclic voltammetry, UV absorption spectra and fluorescence spectra in detail.Experimental results showed that:â‘ . Zn(salph)'s tetrahydrofuran solutionemitted intensive blue-green fluorescence at peak wavelength of 508 nm under UV excitation and had high fluorescent quanta efficiency; HOMOlevel, LUMO level and optical gap of Zn(salph) is -5.24eV, -2.60eV, 2.64eV,respectively.â‘¡. Zn(salhex) powder emitted blue-green fluorescence whichthe maximum emission peak is at 485nm, FWHM(FWHM: Full Wave atHalf Maximum) is 66.6nm and CIE(CIE: Commission International deL'Eclairage) coordinates were x=0.225 0 and y=0.324 7; HOMO level,LUMO level and optical gap of Zn(salhex) is -6.25eV, -3.39eV, 2.86eV,respectively.3. Double-layer device ITO/NPD/Zn(salhex)/Al using Zn(salhex) asthe emissive layer and Double-quanta-well device ITO/CuPc/Alq₃/Zn(salph)/Alq₃Zn(salph)/Alq₃/Al using Zn(salph) as the emissive layerwere fabricated and investigated by vacuum evaporation, respectively.4. Besides, other four Schiff base organic metal complexes weresynthesized and their fluorescence emission spectra were compared withZn(salph)'s to explore luminous mechanisms of them primarily.