| Organic light-emitting diodes (OLEDs) also named organic electroluminescence devices have many advantages such as self light-emission, fast response, full solid device, easy fabrication, high efficiency, wide view-angle, super-slim, wide operation temprature, flexible et al. Therefore, OLEDs are considered as the most ideal and potential display technology of next genaration. But now some main problems should be solved such as high fabrication cost, low lumiance efficiency and short lifetime. Thin Film Transistor (TFT)-OLED technology is indispensable for OLED future industrialization, but TFT technology for OLED is not mature enough to realize large area device at current stage. This greatly affects the pace of industrialization of OLED devices. Aiming at these problems, some basic and systematic works have been performed to focus on the fabrication process to obtain high resolution OLED with passive matrix driving method and fabricate the OLED on TFT backplane using shadowmask technology in this work.1. Due to the lack of red light-emitting dyes for OLEDs, a red OLED which based on a new classof red fluorescent dye of [7-diethylamino-3-(2-thienyl)chronmen-2-ylidene]-2,2-dicyanovinylamine (ACY), by using spin-coating method, with a structure of indium-tin-oxide(ITO)/poly(N-vinylcarbazole) (PVK):ACY(x wt%)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/tris(8-quinolinolato) aluminum (Alq3)/Mg:Ag/Ag was fabricated. Moreover, the effect of different solvents on device performance was also discussed. As a result, red light emission with a maximum luminance of 1120 cd/m2, the CIE coordinates of (0.56,0.40) and a maximum luminance efficiency of 0.27 lm/W were achieved by using a solvent of trichloromethane with a doping ratio of PVK to ACY of 0.7 wt%. Based on theoretical analysis, the further improvement of device performance was proposed.2. High resolution substrate pattern (2.0 inch,128×3×160 pixels) for OLED backplane can be used as passive matrix OLED devcie was designed based on Solomon’s SSD1335 OLED driver.The mask design including four photomasks such as Cr pattern, ITO pattern, insulator pattern and separator pattern and three shadow masks such as organic open mask, organic RGB mask, metal open mask was performed, passive matrix OLED (PMOLED) panel was prepared using the patter design.3. The driver ciruit for fullcolor PMOLED with a resolution of 128x160,256-step brightness control and 65k color was produced based on Arm7 embedded microprocessor LPC2138. Using the driving circuit the display panel from Ritdisplay Company and our display panel was compared. Big difference of driving current was observed. It indicated that there were leak current of OLED display panel. To solve the problem of leak current, a mathematical model of leak current problem was suggested. By Analyzing the mathematical model, we found that the leakage current is between the situation that all scanning lines are lit and only one scanning line is lit. It indicated that there are relationship with OLED’s rectifying behavior. And the requirement of PMOLED display panel’s rectifying behavior was analyzed. To analyze the reason of leak current, we improved the process of making the PMOLED back plane and modified the strcuture of OLED device.At last the leak current was decreased as low as 4.4 mA. The solution of leak current is below:1). Double insulator layers were prepared instead of one single insulator layer;2). Using high power plasma treatment process to modify roughness of ITO surface;3). Introducing a thicker HIL layer with PIN structure to modify the roughness of ITO surface.4. A white OLED mixed with blue and yellow OLEDs drived by low voltage was proposed. The stucture is:ITO/m-MTDATA(100nm):F4-TCNQ (3%)/NPB(200 nm)/NPB (6 nm):DCJTB(1%)/AND (34):TBPe (1%)/BeBq2/LiF (0.5 nm)/Al (150 nm) The device shows a maximum luminance of 38000 cd/m2, a maximum current efficiency of 10.02 cd/A at a bias of 10 V. The CIE Coordinates of device are (0.29, 0.34). And this prototype device was applied to making white PMOLED display successfully.5. A novel kind of TFT backplane was used to make AMOLED dsaplay. The integration of TFT backplane and OLED device was discussed, and the scheme of integrating OLED device to TFT back plane was proposed. The integration layer was realized between TFT back plane and OLED device. The composite cathode of top emitting OLED was optimized. The RGB OLED devices with (hole injection layer, HIL) structure were achieved to improve device efficiency. To solve the problem of microcavity effect, optimized RGB top emitting OLEDs were fabricated by adjusting the film thickness of HIL layer. To further improve the efficiency top emitting device, ETL material BeBq2 was introduced into OLED device. A 4 inch AMOLED display panel with a resolution of 320×240 was achieved by using the opimized device structure consisted of HIL layer and new ETL layer. |
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