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