Organic light emitting material and device

Abstract

The invention relates to the technical field of organic electroluminescent devices, and discloses an organic light emitting material and an organic light emitting diode (OLED) device comprising the same; wherein the HOMO of the organic light emitting material is perpendicular to LUMO. The provided organic light emitting material has a structure represented by the formula (D); in the structure, anelectron donating group and an electron withdrawing group form an electron push-pull co-plane, a rigid molecular structure is obtained, HOMO-LUMO can be separated to a certain state; the consistency between the structure of excited molecule and structure of ground state molecule is high, a retarded fluorescence effect can be obtained, and the luminescent efficiency is high.

Description

technical field [0001] The invention relates to the technical field of organic electroluminescence devices, in particular to an organic light-emitting material and a device. Background technique [0002] Regarding the development of OLED light-emitting materials, the first-generation OLED light-emitting materials are fluorescent OLEDs, and the second-generation OLED light-emitting materials are phosphorescent OLEDs. TADF thermally delayed fluorescence is the third generation of OLED light-emitting materials. TADF thermally delayed fluorescence is a kind of pure organic electroluminescent material that does not contain heavy metals, and its internal quantum efficiency is close to 100%. It is currently the most advanced optoelectronic material. [0003] Under the action of an electric field, the OLED generates a singlet S1 exciton and three triplet T1 excitons. The first generation of fluorescent OLEDs is chemically forbidden due to the difference in spin between the S1 sing...

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Problems solved by technology

However, the transition rate Kr of S1→S0 is an index that is inversely proportional to ΔEST. The smaller ΔEST is, the smaller Kr will cause the electronic transition of S1→S0 to become forbidden.

Therefore, the traditional TADF molecular structure (D-A type or D-A-D, A-D-A, etc.) causes a contradiction in material design, that is, to obtain TADF delayed fluorescence, it is necessary to reduce ΔEST, but Kr also becomes smaller, which affects luminescence

[0005] At present, the focus of TADF development is to reduce the value of ΔEST (splitting energy between singlet and triplet states). The theoretical strategy adopted is to separate the HOMO-LUMO orbitals and reduce the exchange energy integral between singlet and triplet states. Molecular design requires The Donor unit (D) and the Acceptor (A) are separated in physical space. However, although this separation achieves the purpose of HOMO-LUMO orbital separation, it brings about the degradation of other aspects of the material: 1 ) FWHM half maximum width exceeds 50nm; 2) (S1→S0) electronic transition rate Kr decreases, becoming a transition barrier, reducing luminous efficiency

[0006] At present, the molecular structure of TADF materials determines that it cannot obtain narrow-band optical characteristics. This is because the chemical structure of TADF materials is D-A separation, HOMO-LUMO separation, resulting in excited state molecules (S1, T1) Structural relaxation (Structural relaxation) causes Stokes shift in the spectrum, thus forming a FWHM of 60-100nm

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