Nitrogen Heterocyclic TADF Compounds for OLED Efficiency
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Solution Overview
Problem
Current organic electroluminescent materials, particularly phosphorescent materials, face efficiency and lifespan issues, especially for blue phosphorescent materials, and there is a need for novel thermally activated delayed fluorescence (TADF) materials with enhanced performance to rival phosphorescent materials without rare metal elements.
Innovation Solution
Development of nitrogen-containing heterocyclic compounds with specific molecular structures that can be used in organic photoelectric apparatuses, including OLEDs, to facilitate efficient light emission by optimizing the energy level difference between singlet and triplet states, enabling reverse intersystem crossing and radiative decay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials are used in OLED light-emitting layer, then quantum efficiency can reach 100% by utilizing both singlet and triplet excitons, but material cost increases due to rare metal elements and lifespan issues occur especially in blue phosphorescent materials
Solution Approach 1:
The patent modifies molecular parameters by designing specific heterocyclic structures with electron-donating and electron-withdrawing groups to achieve small S1-T1 energy gaps, enabling efficient reverse intersystem crossing and high quantum efficiency without rare metals, thus resolving the contradiction between efficiency and material composition
Solution Approach 2:
The patent replaces expensive rare metal phosphorescent materials with organic TADF materials containing common elements (C, H, N, O), achieving comparable quantum efficiency at lower cost, effectively applying the principle of substituting expensive materials with cheaper alternatives that maintain performance
2Ease of manufacture
If fluorescent materials are used in OLED light-emitting layer, then material cost is reduced compared to phosphorescent materials, but only 25% of singlet excitons can be utilized resulting in lower quantum efficiency
Solution Approach 1:
The patent changes the energy level parameters of the light-emitting material by introducing specific heterocyclic structures with optimized electron-donating and electron-withdrawing groups, achieving small S1-T1 energy gaps that enable efficient reverse intersystem crossing, thus achieving high quantum efficiency comparable to phosphorescent materials while maintaining the cost advantage of organic materials
Solution Approach 2:
The patent introduces triplet excitons as an intermediary state that can undergo reverse intersystem crossing to singlet excitons, which then emit photons radiatively. This intermediary mechanism allows utilization of both singlet and triplet excitons for light emission, achieving high quantum efficiency without requiring rare metal phosphorescent materials
3Ease of manufacture
If existing TADF materials are developed to replace phosphorescent materials, then rare metal elements are eliminated reducing material cost, but the types of TADF materials are limited and performance enhancement is needed
Solution Approach 1:
The patent segments the TADF material structure into distinct functional components: electron-donating groups (e.g., carbazole, triphen胺), electron-withdrawing groups (e.g., triazine, pyrimidine), and heterocyclic linkers. This modular segmentation allows systematic combination of different groups to create diverse TADF material types with optimized properties for various applications
Solution Approach 2:
The patent creates composite TADF materials by combining electron-donating heterocyclic groups with electron-withdrawing heterocyclic groups through covalent bonding, forming new molecular structures with tailored HOMO-LUMO gaps and S1-T1 energy differences, thus expanding the variety and adaptability of TADF materials beyond existing types
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed nitrogen-containing heterocyclic compounds enhance light-emitting efficiency and reduce material costs by achieving comparable performance to phosphorescent materials while eliminating the need for rare metals, with improved stability and efficiency in organic photoelectric devices.
Implementation Method 1
the thermally activated delayed fluorescence (TADF) material. Such a material presented a relatively good light-emitting performance. The band gap value of the S1 state and the T1 state of the TADF material is relatively small; and the lifespan of the T1 excitons of the TADF material is relatively long. Under a certain temperature condition, the T1 excitons may have a reverse intersystem crossing (RISC) to achieve the T1→S1 process
Implementation Method 2
The fluorescent materials are only able to use 25% of singlet excitons (S1), which can be back to the ground state S0 by a radiative transition
Data Source
AI summary
The present disclosure provides a nitrogen-containing heterocyclic compound having a general formula (I) and an organic photoelectric apparatus thereof. The general formula (I) iswherein A1, A2, A3, A4, A5, A6, A7, A8, A9, and A10 are independently selected from a hydrogen atom, at least one compound having the general formula (II) and at least one compound having a general formula (III),wherein Y1, Y2, and Y3 are independently selected from C and N; and R3 and R4 are independently selected from C6-30 aromatic group and C2-30 heterocyclic aromatic group,wherein X is selected from oxyl group, sulfenyl group, substituted or non-substituted imino group, substituted or non-substituted methylene group, and substituted or non-substituted silicylene group, and R5, R6, R7, R8, R9, R10, R11, and R12 are independently selected from hydrogen, deuterium, C1-30 alkyl group, C6-30 aromatic group, and C2-30 heterocyclic aromatic group.