| Organic light emitting devices (OLEDs) have attracted considerable attention due to their outstanding superiorities of application in flat-panel displays, such as self-luminous, high-brightness, wide viewing angle, thinness, low power consumption, fast response time, flexible, and full color. The performance of OLEDs has been improved significantly with the adoption of suitable device structures, process technologies, and organic materials. In full color display, highly efficient and stable green OLEDs have been realized. Compared with green-emitting devices, the electroluminescence (EL) characteristics of blue and red-emitting ones have to be improved particularly in terms of efficiency and color purity for full color applications. On the other hand, white light devices among various colors draw particular attention because their potential use in backlight, full color applications, as well as in lighting purposes. The products of OLEDs have been commercialized, however much work remains important to enhance the product performance. In this dissertation, some works have been shown to improve the performance of OLEDs. It includes the following items:(1) Several 9, 10-diaryl substituted anthracene derivatives were synthesized by a simple synthetic route from anthraquinone compared with conventional method. In this way it is of less reacting steps, convenient, easy to obtain raw material, not need to use expensive palladium catalyst, and of high yield of the product. It is also shown a simple way to synthesize the intermediate product 3, 5-(diphenyl) bromobenzene by one-pot reaction of 2,4,6-tribromoiodobenzene with aryl-Grignard reagent, which is beneficial to industrial manufacture.Blue organic light emitting devices were prepared based on undoped 9, 10-diaryl substituted anthracene derivatives as light emitting materials. The influences of the thickness of lighting layer, hole transporting layer, and electron transporting layer on emitting spectra were studied. The color purity of devices was improved by using hole blocking layer, resulting in pure blue emission. A deep blue organic light emitting diode which was fabricated by firstly using 9,10-di(2-naphthyl)anthracene (ADN) as a dopant and 4,4'-N,N'-dicarbazole- biphenyl (CBP)as a host. The doping concentration of ADN was optimized, and the Commission Internationale de l'Eclairage coordinates of (0.1516, 0.0836) were achieved in the cell, which is very close to the National Television Standards Committee standard of (0.14, 0.08). Meanwhile, maximum luminance over 6500cd/cm2 and maximum current efficiency of 3.5cd/A were also obtained.(2) This dissertation presents organic light-emitting diodes which generate white emission based on both perylene and 5,6,11,12-tetraphenylnaphthacene (rubrene) doped in 9,10-di(2-naphthyl)anthracene (ADN). The white OLEDs have three kinds of configurations: ITO/TPD(50nm)/ADN: 0.04mol%Rubrene (40nm)/Bphen(25nm)/LiF(1nm)/Al, ITO/TPD (50nm)/ADN: 0.05mol%Rubrene (20nm)/ADN: 0.85mol%Perylene (20nm)/Bphen(25nm)/LiF(1nm)/Al, And ITO/TPD (50nm)/ADN:0.85mol%Perylene:0.005mol%Rubrene (40nm)/Bphen(25nm)/LiF(1nm)/Al. The CIE color coordinates of above devices at 4mA/cm2 are (0.3175, 0.3692), (0.3098, 0.3515) and (0.3064, 0.3888) respectively. Compared with the other two devices, the third device presents white emission with the maximum luminance of 11665cd/m2 at 14V according to luminance efficiency of 2.9cd/A. The third white organic light emitting device was fabricated by doping two color fluorescent dyes in one blue host. In which yellow emission component from rubrene was strengthened due to another dopant perylene. It was found that the blue dopant perylene not only itself emitted but also assisted the energy transfer from ADN to rubrene. Thus, in lower concentration of rubrene the white lighting emission was obtained.(3) Three kinds of red organic light emitting devices (ROLEDs) were configured based on a new synthesized pentacene derivative, 6, 13-di-(3,5-diphenyl) phenylpentacene (PDT), doped in tris-(8-hydroxy-quinolinato)aluminum(Alq3). ITO/TPD (50nm)/PDT (60nm)/Bphen(25nm)/LiF(1nm)/Al(Cell-P) ITO/TPD (50nm)/Alq3 : 3%molPDT(60nm)/Bphen(25nm)/LiF(1nm)/Al(Cell-AP) ITO/TPD (50nm)/Alq3:3mol%PDT: 1mol%rubrene (60nm)/Bphen(25nm)/LiF(1nm)/Al (Cell-APR) Although the color coordinate is (0.6581, 0.2927) in Cell-P, the maximum luminance is 3.5cd/m2. The luminance of Cell-P is poor. While the color coordinate is (0.5901, 0.3804) at 4mA/cm2 according to luminance efficiency of 1.5cd/A in Cell-AP. In order to improve the color purity of red emission in Cell-AP, 5,6,11,12-tetraphenylnaphthacene (rubrene) was introduced as the assist dopant in above doping system (Alq3:PDT). The assist dopant (rubrene) not only itself emitted but also assisted the energy transfer from the host (Alq3) to the red emitting dopant (PDT). A stable red emission cell was obtained, and the color coordinates have only small variation from (0.612, 0.371) to (0.6018, 0.3814) with increasing the current density from 12 mA/cm2 to 200 mA/cm2. The excitation mechanism of PDT in Cell-APR may be considered to be both energy transfer from rubrene and PDT directly carrier trapping. So we may deduce that it is attributed to rubrene assist effect which is beneficial to energy transfer from Alq3 to PDT in the same emitting layer, resulting in stable red emission.(4) It is very important to obtain accurate data of energy band structure of organic electroluminescent materials. Cyclic voltammetry is one of the methods usually used to obtain HOMO energy level. However it is too difficult to get precise data of HOMO energy level by cyclic voltammetry. In this dissertation technology of linear scanning voltammetry (LSV) is instead utilized to attain a result of oxidation potential (or HOMO energy level) due to electrochemical oxidation of organic electroluminescent material filmed on the working electrode. Fewer amounts of materials are consumed in this method. And results show that it is faster and more convenient.
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