ZnO As A Electrode Modification For Improvement In Efficiency Of Organic Electroluminescent Devices

In the past decade, the study and application of organic light-emission has seen signification progress. Organic light-emission device have many advantages such as their thinness, self light-emission, broad viewing angle, quick response, easy fabrication, low driving-voltage, low energy-consumption, low cost, etc. It is therefore very possible that will become the next generation panel displays. Recent advances in their development and application are reviewed.But the efficiency of OLED is not high. This has become to be a limitation for the development of its application. In this article, we recall the OLED's development history at first, and then introduce some general fabrication and materials which often are used in experiments and analyze the basic theory of OLED. At last, a new fabrication is devised to rise the efficiency of the OLED.The new kind devices contain two type fabrications: One is cathode modification devices; The other one is anode modification devices. Contrasting the news with the old, ITO/NPB/ ALQ 3 / AL, we can find the one with cathode modification devices, ITO/NPB/ ALQ 3 /ZnO/AL, is worse. While, the anode modification devices, which fabrication is ITO/ZnO/NPB/ALQ 3 /AL, is much better than the older in the light-efficiency and have a higher break-down voltage.The reason to this phenomenon may be concluded to two aspects: The first is ZnO anode modification layer can block the hole's injection at the interface of anode and the hole transporting layer, because Valance band of ZnO is about 7.9 eV, much higher than NPB's. This can be attributed to the more balanced carriers concentration in emissive layer and raise the EL efficiency; the second one is the ZnO anode modification can improve the interface of ITO and NPB. This make the drain current reduce and get a high efficiency.