The Study Of Fabrication Technics And Structure Optimization Of Organic Light-emitting Devices

Organic light-emiting device (OLED) is a very attractive candidate as thenext generation flat panel displays (FPD). The technology exhibits brightprospect in photoelectricity filed owing to its advantages of low DC drivevoltage, active luminescence, full color, high brightness, long lifetime, lightweight, low power consumption and high efficiency. Nowadays, OLED hasbeen commercially produced in the area of mobile meters, screens of mobilephones and digital cameras, etc. However, some problems, especially onstability and lifetime, still need to be resolved.This paper aims at systematic studying such key techniques as thepreparations of organic thin films, the film-thickness control, the OLEDfabrication and its structure optimization.The evaporation source was designed and fabricated. In order to improvethe temperature of the evaporator source's equality, it has a radiate tungstenfilament heater of diameter 0.4mm at the ektexine of the quartz crucible whichdistributed into up tightness and down sparseness to make the temperature uphigh and down low. At the top of the quartz crucible, there was a baffle ofdiameter 2mm which make the vaporing rate of the evaporator source steady.Using(N, N'-bis(salicylidene)-ethylenediamine)zinc (Zn(salen)) aslight-emitting material, the OLED fabrication by the vacuum evaporation was studied, and the optimized evaporation condition was defined. The experimentalresults show that the better device performance could be obtained under theprecipitation system's degree of the vacuum, the organic thin-film's rate of thesedimentation velocity, the temperature of ITO substrate and so on. The rate ofthe emitting layerr was 0.3nm/s. when the precipitation system's degree of thevacuum at 2×10^-3 Pa and the temperature of ITO's underlay at 150℃theOLED has a better performance.The encapsulation which influence OLED performance greatly wasdiscovering by making the observation and testing encapsulation device. Thesimple encapsulation (the film encapsulation and board encapsulation.etc.) wasable to restrain the emergence of dark spots and extend lifetime of device at thecertain degree, but it could not completely prevent the failure device occurring.The permeance of water vapor and oxygen were important index whichinfluence the optical and electrical characteristics of the device.On the basis of the investigation of the key techniques on the organic thinfilms preparations, film-thickness control and device fabrication, the OLED withdouble quantum-well structure and insert layer structure which was superior tothe conventional structure device were designed and studied, and the two typesof devices performance were analyzed. Therefore, the key factor to improve theOLED performance lies in optimizing its structure.