LED and OLED: a lamp and a piece of clothing

LEDs can last for more than 100,000 hours, and a person can use a lamp for a lifetime. OLED has special flexibility, the future clothes are the display screen, what kind of color is displayed, what kind of color can be displayed, one 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; the transparent window can let the light shine in during the day and become a light source at night; the navigation information can be played through the car windshield. The beauty of these future electronics products is due to OLED technology. Therefore, OLED will eventually dominate the field of display and lighting in the future.

OLED working principle

OLED refers to a phenomenon in which an organic semiconductor material and a luminescent material are driven by an electric field to cause luminescence by carrier injection and recombination. The principle uses ITO transparent electrode and metal electrode as the anode and cathode of the device respectively. Under a certain voltage, electrons and holes migrate to the luminescent layer through the electron and hole transport layers, respectively, and meet in the luminescent layer to form excitons. The luminescent molecules are excited and the luminescent molecules emit visible light through the radiation. Radiation light can be observed from the ITO side, and the metal electrode film also functions as a reflective layer. From the current state of development of organic point excitation optical components, green light, blue light, and red light have related materials research and development, among which green light technology is the most mature.

White light OLED

There are two main methods for realizing white OLEDs for illumination: one is wavelength conversion, which uses blue-emitting OLEDs to excite yellow, orange, red fluorescent or phosphorescent powders to achieve white light. Second, the color mixing method is a method of realizing white light by doping or multi-layering by using two kinds of blue light and orange light to compensate light or three primary colors of red, green and blue.

The theoretical light effect of OLED can reach nearly 200lm/w; the industrial target of OLED in lighting application is 1.000cd/m2, which is 50~80lm/w; currently, the efficacy of white OLED products for illumination can reach 60lm. Above /w, the color rendering index is around 80.

OLED lighting applications

Utilizing the large-area advantages of OLED lighting, large-area OLED light sources can be installed on ceilings and walls, so that the entire ceiling and wall surface emits a soft light on the whole surface, instead of being partially illuminated like a light bulb or a fluorescent light, so that the light source allows People feel more gentle and comfortable.

In addition, with the design of the luminaire mechanism, a hanging luminaire can be produced, and an illuminating device with an adjustable angle can be presented. You can also use OLEDlighting's light and thin features to design a luminaire in addition to the sheet-like lighting, so that the luminaire can be swayed with the wind, so that the general lighting can show different lighting moods. OLED lighting allows for greater freedom in design of lighting fixtures, allowing lighting to present more application scenarios.

OLED and LED lighting comparison

From the perspective of lighting demand, LEDs are point-lighting, and the lighting is concentrated. It is more conspicuous when used in outdoor environments, and is suitable for local area lighting, advertising signs, traffic warning signs and other applications. OLEDs are surface-emitting, the light is softer and more uniform, and the effect is better indoors. Both have their own strengths.

From the perspective of luminaire design, LED heating is concentrated, and it is necessary to add a lampshade, heat sink, light scattering device, etc. The luminaire design is more complicated: the OLED's planar light source characteristics, in addition to suitable for various types of luminaire design, the heat dissipation performance is also added, not Additional heat sink components must be added to increase the cost of the fixture. In the future, OLED light-emitting of flexible substrates will be realized, and more and more imaginations will be created by lighting designers.

From this point of view, OLED is even better.

In terms of optical efficiency, the luminous efficiency of LED chips can reach 120lm/W or more. When additional lamps are installed, the actual efficiency may drop to about 60~70lm/W due to the effects of lampshades and light scattering. OLED lighting can only be used at present. To achieve 30~50lm/W, there is still a big gap, and the performance difference between different materials is large. Further efforts are needed in material research and device structure design.

In terms of cost creation, LEDs have gradually narrowed the gap with traditional lighting as the scale of production capacity has expanded and technology has progressed. The price of OLED lighting is still too high, mainly because of the high cost of OLED lighting materials, coupled with the failure of the mainstream evaporation process efficiency, so the material utilization rate is not high, and thus the production cost of OLED lighting is raised.

In terms of product life, LED lighting can theoretically reach 100,000 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 restricting its market. The most serious obstacle to the application, if OLED lighting applications are to be popularized, it must further improve its life. The initial goal is to reach the level of fluorescent lamps, that is, 20,000 hours, and the future goal is to reach 50,000 hours. To achieve this goal, There is a big breakthrough in materials and further advancement in device structure and process.

In general, OLED and LED are both solid-state lighting, which have the advantages of low heat generation, low power consumption, fast response, small size, shock and wear resistance, and easy development into light, short and short products, but in terms of technology maturity and commodities. In terms of technology, there is still a certain gap with LED.

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