Research and development status of organic light-emitting diode industry

Organic light emitting diode (OLED) since inception, due to its many advantages and is widely regarded as the most promising next-generation display technology, the LCD and solid state lighting also show potential application prospect. Low cost, low energy consumption of the organic light emitting diode advantages and characteristics of flexible bending, the light-emitting diode display, LCD backlight in the next generation of solid-state lighting and three core areas showing a huge market has attracted many companies to participate in the OLED industry has greatly promoted the progress of. In the past ten years, the average efficiency of OLED has doubled every year, in line with LED's Haitz law. In general, the OLED industry has three main areas, one is the OLED materials and devices as the center; the two is based on the concept of manufacturing method of OLED panel, as the center; three is a method of driving a display device such as the center of the field. This paper mainly from the aspects of machine parts and materials.

At present, there are many domestic and foreign manufacturers and laboratories engaged in research and development of OLED materials and display devices, from the material point of view, there are 3 main types: one is that polymer materials camp technology company, Royal PHILPS and Japan Sumitomo chemistry as the representative of the British Cambridge; two is a small molecule camp at Eastman Kodak, universal and as the representative of the Japanese Idemitsu; the last one is dendritic luminescent material, because of its luminescence properties of fluorescent dyes can be conveniently by changing different core to achieve, also a number of functional groups and surface of different algebraic options to get some interesting properties, such as carrier transport function, regional isolation effect and the solubility and antenna effect, the most important is that this kind of material with high performance polymer solution processing and small molecular materials It has been considered as the third most developed material system. For any material system, there are two major problems: one is how to obtain high efficiency; two is the life and stability, such as long time still picture keep; there is a follow-up question is how to get high mobility, low operating voltage, thereby reducing power consumption, to lay a solid the future of low power panel. The efficiency and lifetime of blue light material is always the bottleneck, and in May 19th 08 SONY Idemitsu announced jointly developed OLED blue light emitting element, and has confirmed the internal quantum efficiency of 28.5%, and the luminous life for more than 30 thousand hours, on the fluorescent light-emitting materials, the luminous efficiency is the highest level in the world. British Cambridge display technology company and Japan Sumation company announced the blue polymer OLED materials to achieve new and improved, compared to the published in March 07, life expectancy increased by 40%, the blue light material in the initial brightness of 1000cd per square metre half lifetime has reached 10 thousand hours, according to the 400cd brightness per square metre conversion was 62 thousand hour. In order to make the life of the device can be greatly improved, not only to obtain highly efficient luminescent material, also need to improve the hole injection material and electron transporting materials, so as to improve the carrier injection and transport balance, also want to consider the carrier will be effectively limited in the light-emitting layer to further improve the efficiency of the device, 8 hydroxyquinoline aluminum for example by Idemitsu transmission of new materials to replace the traditional (Alq3), effectively reduces the turn-on voltage, improve the efficiency and stability of the device.

In the continuous improvement of monochromatic organic light-emitting materials and devices at the same time, people also consider red, green and blue three basic color composite white light for display, LCD backlight and lighting. Generally speaking, there are two kinds of white OLED technology obtained: the first category is called down conversion (down conversion), the excitation photon by blue or ultraviolet light, each excited unit emits different light after mixing by white; the second category is known as the color mixing, this kind of technology is that by combining two complementary the color of the light (Yellow + blue) or RGB (red + Green + blue) came to light. In the implementation of organic light emitting devices, there are many white light emitting layer device, exciplex / pxciplex composite light illumination device, light emitting devices, micro cavity structure of horizontal or vertical stacked structure, multiple doped WOLEDs / blending single emissive layer white light device. For white light emission layer device, the method of each kind of luminescent materials doped in different layers of the main material of a multilayer various object light emitting device structure, by controlling the current of each composite organic layer, reach the red green and blue emitting layer at the same time to realize white light emitting. For example, American scientists using three layer light emitting layer (3-EML) structure, developed the excellent performance of white OLED, the brightness (luminance) for the maximum luminous efficiency of 1000 CD per square metre of 64 + 3 lm/W color index (CRI) reached 81; CAS Changchun Institute of interfacial modification technology, the use of red, green and blue three light emitting layer structure developed the whole fluorescent white OLEDs with high efficiency, the maximum brightness is more than 40000 CD per square meter, the maximum efficiency reached 20.8 cd/A and 16.8 lm/W, lived for more than 3500 hours in the brightness of 500 CD per square meter. Trichromatic white OLED structure by using vacuum evaporation method, the thickness of each layer can be well controlled so as to obtain the ideal color purity of white light and white light OLED has good performance and are using this structure. In order to ensure that all of the emission from the same emitter layer, a plurality of doped white light emitting devices have to be made of the same dopant