Material composition and function
The properties of organic materials profoundly affect the photoelectric properties of the components. In the choice of anode material, the material itself must have a high work function and opacity, so it has a high work function of 4.5eV-5.3eV, stable and transparent ITO transparent conductive film. It is widely used in anodes. In the cathode portion, in order to increase the luminous efficiency of the element, the injection of electrons and holes usually requires a low work function of Ag, Al, Ca, In, Li, and Mg, or a low work function composite metal. A cathode (for example, Mg-Ag magnesium silver) is produced.
The organic material suitable for electron transport is not necessarily suitable for transporting holes, so the electron transport layer and the hole transport layer of the organic light-emitting diode must use different organic materials. At present, the materials most commonly used to make electron transport layers must have high film stability, thermal stability, and good electron transport properties. Fluorescent dye compounds are generally used. Such as Alq, Znq, Gaq, Bebq, Balq, DPVBi, ZnSPB, PBD, OXD, BBOT and the like. The material of the hole transport layer belongs to an aromatic amine fluorescent compound such as organic materials such as TPD and TDATA.
The material of the organic light-emitting layer must have strong fluorescence in the solid state, good carrier transmission performance, good thermal stability and chemical stability, high quantum efficiency and vacuum evaporation. Generally, the material of the organic light-emitting layer is usually used. The electron transport layer or the hole transport layer are made of the same material, for example, Alq is widely used for green light, and Balq and DPVBi are widely used for blue light.
In general, OLEDs can be classified into two types according to luminescent materials: small molecule OLEDs and high molecular OLEDs (also known as PLEDs). The difference between small molecule OLED and polymer OLED is mainly reflected in the different preparation processes of the device: small molecule devices mainly adopt vacuum thermal evaporation process, and polymer devices adopt rotary coating or spray printing process. Small molecule material manufacturers mainly include: Eastman, Kodak, Idemitsu Kosan, Toyo INK, Mitsubishi Chemical, etc.; polymer materials manufacturers mainly include: CDT, Covin, Dow Chemical, Sumitomo Chemical. There are more than 1,400 patents related to OLED in the world, and three of the most basic patents. The basic patent for small molecule OLED is owned by Kodak Company of the United States. The patent for polymer OLED is owned by Cambridge DisPlay Technology of the United Kingdom and Uniax of the United States.