Deep Red TADF Material for OLED Efficiency
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Solution Overview
Problem
Current organic light-emitting diode (OLED) devices face limitations in achieving high efficiency due to the scarcity of thermal active delay fluorescent (TADF) materials, especially for deep red light, which restricts the utilization of singlet and triplet excitons, and existing heavy metal complex phosphorescent materials are costly and challenging to produce for blue light applications.
Innovation Solution
Development of a thermal active delay fluorescent material with ultrafast reverse intersystem crossing speed and high luminous efficiency, utilizing a molecular structure with a strong electron-withdrawing group as an electron acceptor and a strong electron donor, combined with a specific synthesis method to produce a deep red light TADF material for use in OLED devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If heavy metal complex phosphorescent materials are used to achieve 100% internal quantum efficiency, then singlet and triplet excitons can be simultaneously utilized, but the materials are costly and difficult to manufacture, especially for blue light applications
Solution Approach 1:
The patent replaces expensive heavy metal complex phosphorescent materials with organic TADF materials that are cheaper and easier to manufacture. The TADF materials use common organic compounds with donor-acceptor structures instead of precious metals like iridium and platinum, making them economically viable for large-scale OLED production while maintaining high efficiency
Solution Approach 2:
The patent changes the material composition parameters by using organic compounds with specific donor-acceptor molecular structures instead of heavy metal complexes. This parameter change enables the material to achieve TADF characteristics with ultrafast reverse intersystem crossing rates, maintaining 100% IQE while improving manufacturability
2Ease of manufacture
If fluorescent materials are used in OLED devices, then the production and processing technology is relatively simple, but the theoretical internal quantum efficiency is limited to 25% due to the 1:3 ratio of singlet and triplet excitons
Solution Approach 1:
The patent creates a composite material system combining electron donor and electron acceptor units in a single TADF molecule. This composite structure enables both simple processing like fluorescent materials and high efficiency by facilitating reverse intersystem crossing from triplet to singlet state, allowing simultaneous utilization of all excitons
Solution Approach 2:
The patent changes the energy level parameters by designing molecules with small singlet-triplet energy gaps (ΔEST), which enables ultrafast reverse intersystem crossing rates (kRISC). This parameter optimization allows the material to achieve 100% internal quantum efficiency while maintaining ease of manufacture
3Loss of energy
If TADF materials with small singlet triplet energy level difference are designed to enable reverse intersystem crossing, then triplet excitons can return to singlet state and illuminate, achieving 100% IQE, but such materials with ultrafast reverse intersystem crossing speed and high luminous efficiency are still relatively scarce
Solution Approach 1:
The patent segments the molecular structure into distinct electron donor and electron acceptor units connected by linker groups. This segmentation allows independent optimization of each unit to achieve desired energy levels and ultrafast reverse intersystem crossing rates, systematically generating high-performance TADF materials
Solution Approach 2:
The patent synthesizes composite TADF molecules by combining various electron donor groups (such as carbazole, triphen胺) with electron acceptor groups (such as triphenylene, perylene) through linker units. This composite approach creates a library of materials with optimized properties for deep red light emission and ultrafast kinetics
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 deep red light TADF material enables 100% internal quantum efficiency by facilitating the conversion of triplet excitons to singlet excitons, enhancing the luminous efficiency of OLED devices and overcoming the limitations of existing materials.
Implementation Method 1
triplet excitons can return to the singlet state through the reverse intersystem crossing (RISC), and then illuminate by the radiation transition to the ground state
Implementation Method 2
triplet excitons can return to the singlet state through the reverse intersystem crossing (RISC), and then illuminate by the radiation transition to the ground state
Implementation Method 3
thermal active delay fluorescent (TADF) material
Data Source
AI summary
A thermal active delay fluorescent material includes a structural formula in formula 1:wherein in the formula 1, R is a chemical group of an electron donor.The application adopts a strong electron-withdrawing group of a large conjugate plane as an electron acceptor, and combines an electron acceptor with a strong electron donor to achieve a deep red light thermal active delay fluorescent material with a typical TADF characteristics and a low energy level. The thermal active delay fluorescent material of the application is a deep red light TADF material having a lower single triplet energy level difference, an ultrafast reverse intersystem crossing speed and a high luminous efficiency, and when it is used as a luminescent material for an organic light-emitting diode device, it can promote a luminous efficiency of the organic light-emitting diode device.