Triazines generally refers to a six-membered heterocyclic compound containing 3 nitrogen atoms, and is generally divided into three structures: 1,2,3-triazine, 1,3,5-triazine and 1,3,4-triazine. The triazines conforms to the 4n+2 rule of Huckel's rule and possesses 6 delocalized electrons. All the atoms of triazines are in the same plane and have an aromaticity similar to that of a benzene ring. These characteristics make triazines have strong electronic conductivity, good spatial symmetry and easy modification properties. Introducing a triazine unit into the molecular framework as the core of the conjugated molecule can not only improve the electron injection and transport properties of the molecule, but also improve its thermal stability. Therefore, triazines are often used in the field of optoelectronic devices as electron transport materials, host materials, and light-emitting materials.
Figure 1. Chemical structures of triazines
- Host material: When preparing light-emitting devices, phosphorescent materials need to be doped into the host material to prevent quenching. The host material is generally required to have a higher triplet energy level. Triazine derivatives contain nitrogen atoms with high electronegativity, have strong electron-withdrawing properties, and have high tertiary energy levels. Therefore, triazine derivatives can be used as ambipolar transport host materials to prepare phosphorescent devices with high external quantum efficiency.
- Electron transport materials: Electron transport materials require that the material structure be an electron-deficient system with strong electron accepting ability. Triazine materials have strong electron withdrawing ability, large electron affinity and good thermal stability, and are widely used in the field of electronic devices as electron transport materials.
- Light-emitting materials: Triazine materials have excellent thermal stability. Through reasonable design, triazines light-emitting material with high quantum yield, good thermal stability and excellent processing performance can be obtained. In particular, triazine materials can also be used as delayed fluorescent materials to prepare organic light-emitting diode devices, which greatly improves the external quantum yield of light-emitting devices.
- Xu Liu, Ming Sang, He Lin, Chengfang Liu, Jialing Zhang, Jianpeng Yi, Kun Gao, Wen‐Yong Lai, Wei Huang. Donor–Acceptor Type Pendant Conjugated Molecules Based on a Triazine Center with Depressed Intramolecular Charge Transfer Characteristics as Gain Media for Organic Semiconductor Lasers [J]. Chem. Eur. J., 2020, 26, 3103-3112.