Study On Film Encapsulation For Organic Light-emitting Devices

Organic Light-Emitting Display(OLED)is considered as one of the next generation display techniques with brightest futures. This exciting new technology offers the possibility of efficiency, all solid state, active mission, high brightness, high contrast, wide visual angle, slim thickness and low voltage DC drive etc.. Now there are yet some defects with OLED technology, among which the short lifetime ranks the first. Thus it still takes some time for OLED to replace LCD widely. The valid encapsulation of OLED is the most effective way for solving this problem. We undertook the following researches on OLED encapsulation:1. According to the synthesis mechanism of parylene film material, we designed a set of vacuum chemical vapor deposition equipment with the maximum deposition area of 5cm×5cm.2. We deposited parylene films separately under various conditions with the equipment, and tested corresponding qualities by SEM, IR, the water permeability test and UV-vis. Then we studied the impact of deposition conditions (factors like deposition pressure and reaction time etc.) on the deposition speed, composing and mechanical property and film quality etc. of the films. The experiments show that the best deposition condition for poly-p-xylylene (PPX) film is under pressure P≤5Pa and reaction time is 10min～30min. The film made under this condition has surface with uniform and delicate grain and dense texture, water permeability 0.0228 g/m~2·day and visible light permeability as high as 90%. The best deposition condition for poly-2-chloro-p-xylylene (PCPX) film is under pressure P≤5Pa and reaction time is 10min. The film made under this condition has surface with uniform and delicate grain and dense texture, water permeability 0.0041 g/m~2·day and visible light permeability as high as 97%.3. The typical OLED of ITO/TPD(40nm)/Alq3(70 nm)/LiF( 0.8nm)/Al(150nm) was prepared by means of the vacuum deposition method, and was encapsulated by the parylenes film on the VCVD. The results indicate that the lifetime of encapsulated OLED (no matter PPX or PCPX films) can be increased obviously. The lifetime of non-encapsulated OLED in NT is 197 h, which can be 1215 h after encapsulated by PPX film and 1558 h by PCPX. Both of them can prolong lifetime for 6～8 times.4. Besides, to enhance the encapsulation material's mechanical strength, stability and reduce its dielectric constant, we replaced chlorine atom with fluorine atom in the above-mentioned material's structure. Beginning with 2-fluoro-1,4-dimethylbenzene, we synthesized difluoro[2,2]paracyclophane by brominating side chain, quaternary and Hoffmann degradation and proved their chemical structure with ~1H-NMR, MS, IR, element analysis and melting point test separately. We also reviewed the various factors which affect the reaction and groped for the best reaction conditions.