TADF Organic Compounds for OLED Efficiency
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Solution Overview
Problem
Current organic electroluminescent materials, particularly phosphorescent materials, face challenges such as high costs and inefficiencies, especially for blue phosphorescent materials, and there is a need for novel high-performance thermally activated delayed fluorescence (TADF) materials to achieve comparable luminescence efficiency without rare metal elements.
Innovation Solution
Development of a novel organic electroluminescent compound with a specific structure that enables thermally activated delayed fluorescence, characterized by a small energy gap between singlet and triplet states, allowing for efficient reverse intersystem crossing and luminescence, which is used in organic optoelectronic devices as a luminescent layer, host material, or co-doped material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent materials are used in OLED luminescent layer, then internal quantum efficiency can reach 100% by utilizing both singlet and triplet excitons, but material cost increases due to rare metal complexes and blue phosphorescent materials show poor efficiency and lifetime
Solution Approach 1:
The patent modifies molecular parameters by designing specific donor-acceptor structures with particular HOMO-LUMO energy level differences to enable TADF mechanism, achieving high efficiency without rare metals while maintaining stability and lifetime
Solution Approach 2:
The patent creates composite molecular structures combining electron-donating groups and electron-accepting groups in specific configurations to achieve the desired TADF properties, replacing single-component phosphorescent materials with multi-component organic systems
2Use of energy by moving object
If phosphorescent materials are used in OLED luminescent layer, then luminescence efficiency improves by utilizing triplet excitons, but material cost increases due to rare metal complexes
Solution Approach 1:
The patent replaces expensive rare metal-based phosphorescent materials with inexpensive organic compounds that exhibit TADF, eliminating the need for costly iridium or platinum complexes while maintaining high luminescence efficiency
Solution Approach 2:
The patent achieves the desired luminescence efficiency by carefully tuning molecular energy parameters, specifically designing HOMO-LUMO gaps and singlet-triplet energy differences that enable efficient reverse intersystem crossing without requiring rare metals
3Ease of manufacture
If fluorescent materials are used in OLED luminescent layer, then material cost remains low, but external quantum efficiency is limited to 25% by singlet state utilization only
Solution Approach 1:
The patent transforms the material from simple fluorescent to TADF by adjusting energy parameters, specifically creating a small energy gap between S1 and T1 states that enables thermal activation and triplet exciton utilization, achieving up to 100% external quantum efficiency
Solution Approach 2:
The patent designs composite molecular structures with specific donor-acceptor combinations that create the necessary energy level alignment for TADF, combining the low cost of organic materials with enhanced efficiency beyond conventional fluorescence
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 compounds demonstrate high current efficiency and external quantum efficiency, reducing driving voltage and enhancing luminescence performance in organic electroluminescent devices, offering a cost-effective alternative to rare metal-based materials.
Implementation Method 1
T1 state excitons can achieve the T1→S1 process by reverse intersystem crossing (RISC) and then the radiation attenuation from the S1 state to the ground state S0 under a certain temperature
Implementation Method 2
a thermally activated delayed fluorescence (TADF) materials have good luminescence performance. The energy gap between S1 state and T1 state of this material is small, and the lifetime of the T1 state excitons is longer
Implementation Method 3
Fluorescent materials, only utilizing 25% of the singlet state S1 excitons, go back to the ground state S0 by radiative transition
Implementation Method 4
Fluorescent materials, only utilizing 25% of the singlet state S1 excitons, go back to the ground state S0 by radiative transition
Implementation Method 5
The second kind is phosphorescent materials, utilizing not only 25% of the singlet state S1 excitons but also 75% of the triplet state T1 excitons
Data Source
AI summary
The present application provides an organic electroluminescent compound, use thereof in organic optoelectronic device, and an organic photoelectric device comprising the same.