Green TADF Material for OLED Internal Quantum Efficiency
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Solution Overview
Problem
Current OLED devices face limitations in internal quantum efficiency due to the lack of effective green light-emitting materials, particularly in thermally activated delayed fluorescence (TADF) materials that require fast reverse intersystem crossing and high photoluminescence quantum yield, and are scarce in comparison to phosphorescent materials.
Innovation Solution
A green light-emitting TADF material with a small energy gap between the lowest singlet and triplet excited states, achieved through specific molecular structures and synthesis processes, is developed, which includes compounds with electron acceptor and donor groups, and is applied in an organic electroluminescent device to enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phosphorescent materials are used to achieve 100% internal quantum efficiency, then both singlet and triplet excitons can be harvested, but rare metal elements such as Ir or Pt are required
Solution Approach 1:
The patent replaces expensive rare metal phosphorescent materials with organic TADF materials that do not contain Ir or Pt, using readily available organic compounds to achieve the same functional outcome of harvesting triplet excitons
Solution Approach 2:
The patent modifies molecular structures of organic compounds to achieve small energy gaps between singlet and triplet states, enabling efficient reverse intersystem crossing and TADF behavior without rare metals, thus achieving 100% IQE through parameter optimization rather than material substitution
2Reliability
If TADF materials are used to achieve 100% internal quantum efficiency, then both singlet and triplet excitons can be utilized, but there is a lack of TADF materials with fast reverse intersystem crossing and high photoluminescence quantum yield
Solution Approach 1:
The patent designs composite molecular structures combining electron-donating phenoxazinyl groups with electron-accepting groups, creating composite TADF materials that exhibit both fast RISC and high PLQY properties, thereby expanding the available material options
Solution Approach 2:
The patent systematically varies molecular structures by changing electron donor and acceptor groups to optimize key parameters including energy gap (ΔEST), reverse intersystem crossing rate, and photoluminescence quantum yield, thereby developing a series of TADF materials with improved performance
3Device complexity
If fluorescence materials are used in OLED devices, then the device structure is simple, but the internal quantum efficiency can only achieve 25% at most due to the branching ratio of singlet and triplet excitons
Solution Approach 1:
The TADF materials enable the system to self-convert triplet excitons to singlet excitons through reverse intersystem crossing, allowing the material itself to overcome the fundamental limitation of fluorescence materials without requiring additional device components or complex structures
Solution Approach 2:
The patent changes the photophysical parameters of the emitting material from conventional fluorescence to TADF mechanism, enabling triplet exciton utilization while maintaining simple OLED device architecture
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 green TADF material achieves high internal quantum efficiency and is integrated into OLEDs and display panels, providing high-performance and high-efficiency electronic devices by utilizing the compounds in the organic light-emitting layer.
Implementation Method 1
A singlet excited state is generated from the triplet excited state by reverse intersystem crossing (RISC), and the singlet excited state is converted into light emission
Implementation Method 2
high photoluminescence quantum yield (PLQY) are required conditions of the TADF materials
Data Source
AI summary
A thermally activated delayed fluorescence (TADF) material including a compound represented by formula (I). The TADF material can be applied to an organic light-emitting layer, thereby realizing a series of high-performance TADF electronic devices.