TADF Material with Carbazole Units for OLED Efficiency
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Solution Overview
Problem
Current OLED devices face limitations in light emitting efficiency and lifetime, with first-generation materials having low efficiency and second-generation phosphorescent materials suffering from poor blue phosphorescence efficiency and short lifetime, while newly discovered thermally activated delayed fluorescence (TADF) materials offer high efficiency but lack thermal stability and are scarce.
Innovation Solution
A thermally activated delayed fluorescence material combining multi-carbazole and/or phenothiazine units for enhanced thermal stability, along with a simplified synthesis method that allows for high yield and adjustable luminous and thermal properties, is developed, which is used in an OLED device to achieve high fluorescence efficiency and long-term stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phosphorescent material is used to achieve high theoretical conversion efficiency, then light emitting efficiency is improved, but blue phosphorescence efficiency deteriorates and lifetime is shortened
Solution Approach 1:
The patent changes the emission mechanism parameter from phosphorescence to thermally activated delayed fluorescence (TADF), utilizing reverse intersystem crossing to achieve high efficiency without the drawbacks of blue phosphorescence. This parameter change in the发光 mechanism resolves the contradiction between high efficiency and blue phosphorescence performance
Solution Approach 2:
The patent employs composite molecular结构设计 combining electron-donating groups and electron-withdrawing groups to create TADF materials with high efficiency and stability. This composite approach at the molecular level achieves both high light emitting efficiency and reliable blue phosphorescence performance
2Use of energy by moving object
If TADF material is used to achieve high luminous efficiency, then conversion efficiency is improved, but thermal stability deteriorates
Solution Approach 1:
The patent uses composite molecular结构设计 with specific donor-acceptor combinations to create TADF materials that maintain both high luminous efficiency and thermal stability. The composite structure at molecular level enables efficient TADF while improving thermal properties
Solution Approach 2:
The patent introduces specific functional groups (carbazole, phenothiazine) at local positions in the molecular structure to enhance thermal stability without compromising the overall TADF efficiency. This local quality enhancement resolves the thermal stability issue
3Ease of manufacture
If TADF material is used to reduce fabrication cost, then cost is reduced, but material scarcity and imperfect theory worsen development difficulty
Solution Approach 1:
The patent adopts TADF materials that eliminate the need for expensive rare metals like iridium and platinum used in phosphorescent OLEDs. By using abundant organic compounds with TADF characteristics, the fabrication cost is dramatically reduced while maintaining high performance
Solution Approach 2:
The patent changes the material composition parameter from rare metal-based phosphorescent materials to organic TADF materials, making the materials more abundant and cost-effective. This parameter change addresses both cost reduction and material availability issues
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 material achieves high luminous efficiency and extended service life for OLED devices, meeting practical demands while reducing fabrication costs, and the synthesis method provides a cost-effective and stable solution for TADF-based OLEDs.
Implementation Method 1
In 2012, professor Adachi at Kyushu University in Japan found a new material of thermally activated delayed fluorescence (TADF) based on triplet-singlet state transition
Data Source
AI summary
The present invention provides a thermally activated delayed fluorescence material, a method of synthesizing the same and an OLED device using the same. The thermally activated delayed fluorescence material includes a structure formula 1 aswherein the group Ar1 is identical to or different from the group Ar2, and the group Ar1 and the group Ar2 are consisted of carbazole and/or phenothiazine. The thermally activated delayed fluorescence material has a higher glass transition temperature, high thermal stability and excellent luminous efficiency. The method of synthesizing the same has simplified steps, easily purified product, high yield, and luminous and thermal properties of the product can be adjusted by connecting to differentiated functional groups. The OLED device using the same has a light emitting layer of high fluorescence efficiency and long-term stability, so that luminous efficiency and service life of the OLED device can meet practical demand.