Organic electroluminescent compound and organic electroluminescent device

Abstract

The invention provides an organic electroluminescent compound. The organic electroluminescent compound has a structure shown as a formula (I). Compared with the prior art, the organic electroluminescent compound provided by the invention contains a skeleton formed by connecting B with a derivative anthracene type fused ring and a nitrogen heterocyclic ring, has a certain electron withdrawing capability, and is connected with a linker and a donor to form a D-linker-A or D-A type compound; the organic electroluminescent material has a relatively twisted structure, and can reduce the overlappingdegree of HOMO and LUMO, thereby obtaining a relatively small singlet state and triplet state energy level difference, further realizing efficient inverse intersystem jump, enabling more T1-state excitons to jump to an S1 state to emit fluorescence, improving the exciton utilization rate, and achieving relatively high luminous efficiency.

Description

technical field [0001] The invention belongs to the technical field of organic electroluminescent materials, in particular to an organic electroluminescent compound and an organic electroluminescent device. Background technique [0002] As a new generation of display technology, organic electroluminescent materials (OLED) have the advantages of ultra-thin, self-luminous, wide viewing angle, fast response, high luminous efficiency, good temperature adaptability, simple production process, low driving voltage, and low energy consumption. It has been widely used in industries such as flat panel display, flexible display, solid state lighting and vehicle display. [0003] According to the light-emitting mechanism, it can be divided into four types: fluorescent materials, phosphorescent materials, triplet-triplet annihilation (TTA) materials and thermally activated delayed fluorescence (TADF) materials. Among them, fluorescence is the radiative attenuation transition of singlet ...

AI Technical Summary

Problems solved by technology

[0004]According to the spin quantum statistics theory, the formation probability ratio of singlet excitons and triplet excitons is 1:3, so the internal quantum efficiency of fluorescent materials does not exceed 25 % limit, according to the Lambertian luminescence mode, the light extraction efficiency is about 20%, so the EQE of the OLED device based on the fluorescent material is not more than 5%; due to the heavy atom effect, the phosphorescent material can strengthen the molecular internal system through spin coupling Inter-crossing can directly use 75% of the triplet excitons, so as to realize the emission of S1 and T1 at room temperature, and the theoretical maximum internal quantum yield can reach 100%. According to the Lambertian luminescence mode, the light extraction efficiency is 20 %, so the EQE of OLED devices based on phosphorescent materials can reach 20%. Under the current density, there is a serious efficiency roll-off phenomenon in phosphorescent materials, and the stability of phosphorescent devices is not good; TTA materials are based on two adjacent triplet excitons, which recombine to generate a higher-level singlet excited state molecule and A ground state molecule, but two triplet excitons produce a singlet exciton, so the theoretical maximum internal quantum yield can only reach 62.5%. In order to prevent a large efficiency roll-off phenomenon, the triplet excitons in this process The concentration needs to be adjusted; while for TADF materials, when the energy level difference between the singlet excited state and the triplet excited state is small, the reverse intersystem crossing RISC occurs inside the molecule, and the T1 state excitons are upconverted to the S1 state by absorbing the heat of the environment. Using 75% triplet excitons and 25% singlet excitons at the same time, the theoretical maximum internal quantum yield can reach 100%, and it is mainly an organic compound, which does not require rare metal elements, and the production cost is low. chemical modification

However, few TADF materials have been discovered so far, and new TADF materials that can be used in OLED devices need to be developed urgently.

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