The Performances Optimum Of Organic Flourescent & Phosphorescent Devices And Study On The Encapsulation Of OLEDs

Organic light-emitting diodes (OLEDs) possess many advantages, such asself-emission, fast response, full solid device, easy fabrication, high efficiency, wideview-angle, super-thin thickness. OLEDs are considered as the most ideal and potentialdisplay technology in 21^st century. However, currently there are also some shortcomingsto prevent it from large scale commercial application such as high fabrication cost, lowlumiance efficiency and indistinct understanding about device mechanism. Aiming atthose problems, some basic and systematic works have been performed to focus on thefabrication process to obtain high performance red fluorescent OLED device and highefficiency phosphorescent OLEDs in this work. The encapsulation technology of OLEDis also studied.1. The red fluorsecent OLED based on DCJTB was fabricated. There are fiveparameters affecting the properties of fluoresecent OLED and orthogonal test tableL₍16((4⁵) was used to carried out the systematic study. The parameters includes: Thethickness of HTL, thickness of EML, thickness of ETL, doped concentration of DCJTB,doped concentration of Rubrene. The optimum structure for the OLED devices isITO/HIL(50nm)/HTL(40nm)/EML(40nm)/ETL(20nm)/LiF(1nm)/Al(100nm), the dopedconcentration of DCJTB & Rubrene are 1 wt%, 30 wt%, respectively. The luminance(L)-current density (J)-bias voltage (V) characteristics were recorded simultaneouslywith the measurement of a PR650 spectroscan spectrometer by combining thespectrometer with a Keithley 2400 programmable voltage-current source. Thebrightness of OLED prepared with parameters mentioned above is 8650cd/m² under thevoltage of 23.5v, and relative efficiency is 2.58 cd/A @ 6.8v.2. The advantage of organic electro-phosphorescent materials is discussedcomparing with that of organic fluorescent materials. And the differences of energytransferring mechanism in the doping status between the organic electro-phosphorescentmaterials and organic fluorescent materials are also introduced. They are the theories ofF(o|¨)rster energy transfer and Dexter energy transfer. Novel six kinds of phosphorescent materials have been designed and synthesized based Ir. two kinds of phosphorescentmaterials are choosed and relative multilayer devices are fabricated. The thickness ofEML and doping concentration of phosphorescent OLED were optimized. At the sametime the high efficiency phosphorescent OLED was fabricated.3. a novel phosphorescent OLEDs with pure phosphorescent materials as theemitting layer based on new materials platinum(â…¡) (2-phenylpyridinato-N,C2)(3-benzoyl-camphor) [(ppy)pt(bcam)] with red light emission is demonstrated. Becausethe molecular structure of this kind of phosphorescent materials has the3-benzoyl-camphor group with strong steric hindrance effect. It enormously simplifiesthe fabrication processes. The methods can be adapted to the mass production ofphosphorescent OLED; it is the one of novel idea in this dissertation.4. The reasons of the OLED degradation were discussed, and the electrolytic cellmodel to explain the OLED degration is proposed. The three kinds of encapsulationtechnologies are also introduced; they are conventional encapsulation with backplane,vacuum encapsulation with backplane and multi-layer thin film encapsulation; amongthem, the vacuum encapsulation with backplane technology was proposed by us. OLEDdevice of classical structure with ITO/CuPc/NPB/Alq₃/LiF/Al, which was used to studyOLED degradation, is adopted. The OLED devices with three encapsulation methodshave been encapsulated, respectively. The calcium film etching method is choosed tostudy the results of three encapsulations. A good scheme through experimental testresult is obtained.