Light Emitters & Dopants For Semiconductors
In OLED devices, the light emitter is the core of the device. According to the different luminescence mechanism, light emitters can be divided into three types: fluorescent luminescent materials, phosphorescent luminescent materials and rare earth complex luminescent materials. The luminescent material with good electron transport performance and high luminous efficiency is selected as the main light emitters, and then high-performance guest luminescent material is doped as the dopant. The use of dopants improves the luminous efficiency of OLED devices and enriches the colors of the devices. Choose a luminescent material with good electron transport performance and high luminous efficiency as the main luminous body, and then dope with high-performance fluorescent guest optical elements to improve the luminous efficiency of the OLED and obtain optical fibers of different colors. Common dopants include red fluorescent dopants, green fluorescent dopants and blue fluorescent dopants. The electroluminescence of phosphorescent light-emitting materials is to directly introduce the ligand of the phosphorescent complex into the polymer chain, which can reduce the interaction between the phosphors and at the same time suppress the high-concentration triplet spin in the phosphorescent doped system. The extinction of excitons increases the energy transfer between chains and improves the luminous efficiency. This is a spin state exciton in a singlet state and a triplet state, and its internal quantum efficiency can reach 100%. The rare-earth complex luminescent material can also simultaneously use singlet and triplet spin state excitons, and also has extremely high internal quantum efficiency. It can be seen that light emitters and corresponding dopants are very important in OLED devices.
Figure 1. Some light emitters with high luminous efficiency
Applications:
- Color display: Color display is the application trend of OLED. The color display technology of OLED mainly includes RGB pixel juxtaposition method, color conversion method, and color filter film method. The RGB pixel juxtaposition method developed earlier and is currently used more in the industry. The color conversion method is a method that uses blue OLED combined with a light color conversion film, which effectively improves the display resolution and reduces the manufacturing process, but it is only suitable for blue light-emitting materials. The color filter film method requires the use of OLED devices in combination with filters, which can improve display clarity and obtain display devices with larger screen sizes. In the color display, the application of light emitters and dopants can make the color of OLED devices changeable and increase the color purity.
- Full-color device: The color basis of full-color display is the three primary colors of red, green and blue. Many fluorescent materials are not pure enough to emit light, and various color dopants need to be added to them to obtain emission light with high brightness, efficiency, stability and color purity. The use of dopants can not only improve the luminous brightness and color purity of the device, but also improve the luminous efficiency and lifetime of the device, so as to realize the full-color display of the light-emitting device.
Reference
- Jian-Yong Hu,Yong-Jin Pu,Fumiya Satoh,So Kawata,Hiroshi Katagiri,Hisahiro Sasabe,Junji Kido. Bisanthracene-Based Donor–Acceptor-type Light-Emitting Dopants: Highly Efficient Deep-Blue Emission in Organic Light-Emitting Devices [J]. Advanced Functional Materials 2014, 14, 24, 2064-2071.
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