The Study of Electron Transport Layers in Organic Light-Emitting Diodes by Thermal Evaporation and Stamping in Solution Processes

• Main Authors: Apisit Chittawanij, 艾比西
• Other Authors: 莊賦祥
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/jzxu39

博士 === 國立虎尾科技大學 === 光電工程系光電與材料科技博士班 === 104 === This dissertation is about the engineering of high performance OLEDs, which includes the electron transport layer thermal evaporation and stamping in OLED solution-processes. The following work is included in this dissertation: (i) An n-type doping system of tris(8-hydroxy-quinolinato) aluminum (Alq3) doped 2-(hydroxyl) quinolone lithium (Liq) in hybrid white OLEDs is developed and its device performances are compared with the conventional device. The maximum current efficiency of 23.2 cd/A and power efficiency of 7.4 lm/W at 20 mA/cm2 were obtained from the n-type doping HWOLED device. (ii) White OLEDs based on phosphorescent emitters are regarded as potential candidates for future lighting and display applications. In this study three phosphorescent dyes are incorporated, iridium(III) [bis(4,6-difuoro phenyl)-pyridinato-N,C2′] picolinate (FIrpic), tris[2-phenylpyridinato-C2,N] iridium (III) (Ir(ppy)3) and bis[2-(1-isoquinolinyl-N) phenyl-C](2,4-pentanedionato-O2,O4) iridium(III) (Ir(piq)2 acac), into a host of 4,4′-Bis(N-carbazolyl)-1,1′-biphenyl (CBP) to achieve a simple single-emitting white OLED layer using the solution process. The current and power efficiencies of the blue device with FIrpic 20 wt% in chlorobenzene were 2.95 and 0.89 lm/W at 20 mA/cm2. The current efficiency of 3.1 cd/A at 20 mA/cm2 and the CIE coordinates of (0.31, 0.32) at 1000 cd/m2 were obtained from the white device. (iii) To achieve high-performance OLEDs using solution-processing, uniform amorphous film formation is a very important prerequisite, which depends strongly on the solution-process materials. Highly efficient flexible blue OLEDs were fabricated by solution-processing commercial small molecules as the mixed-hosts. The hole transporting 4,4′ ,4″ -tri(N-carbazolyl)triphenylamine (TCTA) doped with the host 2,6-bis(3-(9H- carbazol-9-yl)phenyl)pyridine (26DCzPPy) as the solution-processed mixed-host for flexible blue OLED was investigated. The device with TCTA doped host exhibits the luminance of 2800 cd/m2, current density of 14.00 cd/A and power efficiency of 4.3 lm/W at 20 mA/cm2. (iv) Efficient multilayered flexible blue OLEDs were fabricated using the stamping method with PDMS and release film as transfer film. In order to overcome the mixing problem that occurs between the organic layers during the solution-processes, the stamping method was utilized on a small molecule layer. At the current density of 20 mA/cm2, the flexible blue OLED with PDMS as transfer film stamping device shows current and power efficiencies of 5.2 cd/A and 1.5 lm/W, respectively. The multilayered flexible blue OLEDs manufactured using the proposed stamping method presented significantly over spin-coated devices.