LED and OLED: a lamp and a piece of clothing

The life of LED can reach more than 100 thousand hours, and one person can use one lamp for a lifetime. OLED has special flexibility. The future clothes are the display screen. What kind of color you want to display what kind of color, a person can wear a piece of clothing. Wen Shangsheng, the screen can be bent, the phone can be folded, and the TV screen is as thin as paper; Transparent windows during the day allow light to come in and become a light source at night; Navigation information can be played through the windshield of a car. The beauty of these future electronic products is due to OLED technology. Therefore, OLED will eventually dominate the display and lighting fields in the future. OLED working principle OLED refers to the phenomenon that organic semiconductor materials and luminescent materials cause luminescence through carrier injection and recombination under the drive of electric field. The principle uses ITO transparent electrode and metal electrode as the anode and cathode of the device respectively. Under a certain voltage drive, electrons and holes migrate to the light emitting layer through the electron and hole transport layer respectively, and meet in the light-emitting layer, form excitons and excite the light-emitting molecules, and the light-emitting molecules emit visible light through radiation. The radiated light can be observed from the ITO side, and the metal electrode film also acts as a reflective layer. Judging from the current technological development of organic point-excitation light-emitting elements, green light, blue light and red light all have related material research and development, of which green light technology is mature. There are two main methods for white light OLED to realize white light OLED for illumination: one is wavelength conversion method, it uses OLEDs that emit blue light to excite yellow, orange, red fluorescent or phosphorescent powder to realize white light. Second, the color mixing method is a method that uses blue light and orange light to compensate light or red, green and blue light to realize white light by doping or multi-layer. The theoretical luminous efficiency of OLED can reach nearly 200lm/w; OLED's industrial goal in lighting applications is 1. 000cd/㎡, reaching 50 ~ Efficiency of 80lm/w; At present, the luminous efficiency of white OLED products used for lighting can reach more than 60lm/w, and the color rendering index is about 80. The lighting application of OLED can take advantage of the large area of OLED lighting, and a large area of OLED light source can be installed on the ceiling and wall to make the whole ceiling and wall emit soft light, instead of light bulbs and fluorescent lamps being local lighting, the light source makes people feel milder and more comfortable. In addition, it can also cooperate with the design of the lamp mechanism to produce a hanging lighting lamp, which can present a lighting device with adjustable angle. The light and thin characteristics of OLEDlighting can also be used to design flaky lighting lamps, so that the lamps are so light that they can sway with the wind, and the general lighting can present the lighting feeling of different situations. OLED lighting can make the design of lighting lamps more free, so that lighting can present more application situations. Compared with LED lighting, from the aspect of lighting demand, LED belongs to point lighting, with concentrated lighting, which is more eye-catching when applied to outdoor environment, suitable for local area lighting, advertising signs, traffic warning signs and other applications. OLED is a surface light, the light is softer and more uniform, and the indoor effect is better. Both have their own strengths. Judging from the lamp design, LED heating is concentrated and requires additional lampshades, heat dissipation devices, light scattering devices, etc. The lamp design is more complicated: The plane light source characteristics of OLED, in addition to the design of lamps suitable for various types, the heat dissipation performance is also mixed, and there is no need to add additional heat dissipation elements to increase the cost of lamps. In the future, OLED lighting with flexible substrates will create unlimited imagination for lighting designers. From this point of view, OLED is better. In terms of optical efficiency, the luminous efficiency of LED chips can reach more than 120lm/W. When additional lamps are added, the actual efficiency may drop to 60 ~ due to the influence of lampshades, light scattering and other devices ~ Around 70lm/W; OLED lighting can only be done at present 30 ~ 50lm/W, there is still a big gap, and there is a big difference between different materials. Further efforts are needed in material research and device structure design. In terms of cost creation, LED has gradually narrowed the gap with traditional lighting due to the expansion of production capacity and technological progress and the gradual decline in prices. The price of OLED lighting is still too high, mainly because the cost of OLED lighting materials remains high, coupled with the failure to improve the efficiency of the mainstream evaporation process, so the material utilization rate is not high, thus increasing the production cost of OLED lighting. In terms of product life, LED lighting can theoretically reach 100 thousand hours. Of course, there are problems such as heat affecting life and light decay during use; The life of OLED devices is seriously insufficient, generally only 5000- 8000 hours, which is also a serious obstacle to its market application. If OLED lighting application is to be popularized, its service life must be further improved, the initial goal is to reach the level of fluorescent lamps, I . e. 20000 hours, while the future goal is to reach 50000 hours. To achieve this goal, there should be a big breakthrough in materials and further improvement in device structure and technology. Generally speaking, OLED and LED belong to solid-state lighting, and have the advantages of low calorific value, low power consumption, fast reaction speed, small volume, shock resistance and impact resistance, easy development into light, thin and short products, etc, however, there is still a certain gap with LED in terms of technology maturity and commercialization.