Organic Light Emitting Diode
Organic Light Emitting Diode
Since organic light-emitting diodes (hereinafter referred to as OLED) were published in 1987, thanks to the efforts of researchers from various disciplines such as chemistry, physics, materials science, and optoelectronic science, as well as materials manufacturers, equipment manufacturers, and With the continuous improvement of panel manufacturers, it has reached the stage of commercialization. It is a display technology full of business opportunities after LCD.
Because OLED has the advantages of being self-luminous, thin and light, and can be used on flexible substrates, its applications are not limited to display applications. It is also gradually penetrating into lighting, medical, automotive, wearable devices, etc., and integrating into our lives. .
Because OLED has the advantages of being self-luminous, thin and light, and can be used on flexible substrates, its applications are not limited to display applications. It is also gradually penetrating into lighting, medical, automotive, wearable devices, etc., and integrating into our lives. .
OLED materials can be divided into polymer (polymer (O)LED, PLED) materials and small molecule materials (small molecular OLED). Based on the light-emitting mechanism of the materials, they can be divided into the following categories of materials:
| material type | Fluorescent material (Fluorescence) | Phosphorescent material (Phosphorescence) | Thermal activated delayed fluorescent luminescent materials (TADF material) |
| Features | Theoretical efficiency reaches 25% Achieve full color light without using precious metals and low cost | Theoretical efficiency reaches 100% Deep blue light color has not yet been achieved and the cost of using precious metals is high | Theoretical efficiency reaches 100% The technology is still under development and no precious metals are used. |
| material type | Features |
| Fluorescent material (Fluorescence) | Theoretical efficiency reaches 25% Achieving full color light without using precious metals and lower cost |
| Phosphorescent material (Phosphorescence) | Theoretical efficiency reaches 100% Deep blue light color has not yet been achieved and the cost of using precious metals is high |
| Thermal activated delayed fluorescent luminescent materials (TADF material) | Theoretical efficiency reaches 100% The technology is still under development and no precious metals are used. |
OLED components use evaporation, coating, inkjet or lamination to build multiple organic layers so that electrons and holes are injected from the cathode and anode respectively and combined in the light-emitting layer. Because of the different chemical structures of luminescent materials, different light colors can be produced. For example, the three primary colors of red, green, and blue can be used as panels; different light colors can be combined to form white light as lighting; or pure red can be used as car taillights, etc. .
In order to achieve better efficiency and lifetime, how to allow electrons and holes to smoothly enter the luminescent layer and combine in the luminescent area is a very important issue, including considering the energy level (HOMO_LUMO) difference between adjacent materials, The carrier mobility of each layer of material must also be considered. The following figure is a schematic diagram of the energy levels of the material. With clever energy level arrangement, it can not only reduce the obstacles to charge injection, but also produce a charge blocking effect. Confining the recombination area to the emissive layer.
In order to achieve better efficiency and lifetime, how to allow electrons and holes to smoothly enter the luminescent layer and combine in the luminescent area is a very important issue, including considering the energy level (HOMO_LUMO) difference between adjacent materials, The carrier mobility of each layer of material must also be considered. The following figure is a schematic diagram of the energy levels of the material. With clever energy level arrangement, it can not only reduce the obstacles to charge injection, but also produce a charge blocking effect. Confining the recombination area to the emissive layer.
