OLED Emitting Layer Composition for Efficient Host-TADF Energy Transfer
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Solution Overview
Problem
Existing organic electroluminescent devices face challenges in achieving high brightness per current, desired light spectrum, and suitable lifespan, particularly in the visible light spectrum, with a lack of efficient and stable OLEDs.
Innovation Solution
Incorporating a light-emitting layer comprising a host material, a thermally activated delayed fluorescence (TADF) material, and an emitter material, where specific energy level relationships and ratios are established to enhance energy transfer and emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional OLED structures with single host material are used, then device simplicity is maintained, but illumination level and quantum yield are insufficient
Solution Approach 1:
The patent employs composite materials by combining a host material with a TADF emitter material in the light-emitting layer. This composite approach enables efficient energy transfer from the host to the emitter, achieving high quantum yields and improved illumination levels while maintaining device functionality.
Solution Approach 2:
The patent optimizes the energy level parameters of the host and emitter materials, specifically ensuring that the S1 energy level of the host is higher than that of the emitter, and the T1 energy level of the emitter is lower than the S1 level of the host. This parameter optimization enables efficient energy transfer and achieves high quantum yields.
2Reliability
If existing OLED materials are used, then device structure is simple, but lifetime and stability are insufficient
Solution Approach 1:
The patent uses a composite material system consisting of a host material and a TADF emitter material with specific energy level relationships. This composite structure improves device lifetime and stability by enabling efficient energy transfer and reducing energy loss pathways that would otherwise degrade the device.
Solution Approach 2:
The patent assigns specific functional roles to different materials in the light-emitting layer: the host material provides the energy transfer pathway while the TADF emitter material provides the emission function. This local quality differentiation optimizes each material's contribution to device performance and longevity.
3Illumination intensity
If conventional energy transfer mechanisms are used, then device structure is simple, but illumination level per current is insufficient
Solution Approach 1:
The patent creates a composite light-emitting layer with host and TADF emitter materials that work together to achieve efficient energy transfer. This composite system converts electrical current into light with high efficiency, achieving high illumination levels per current while managing the complexity of the energy transfer mechanism.
Solution Approach 2:
The patent optimizes key energy parameters including the S1 and T1 energy levels of both host and emitter materials. By carefully controlling these parameters to satisfy specific energy level relationships, the system achieves efficient energy transfer and high brightness per current.
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 solution results in an organic electroluminescent device with improved lifetime and quantum yields, exhibiting emission in the visible spectrum.
Implementation Method 1
the lowermost excited singlet state of the host material HB is higher than the lowermost excited singlet state of the emitter material SB, and the lowermost excited triplet state of the emitter material SB is lower than the lowermost excited singlet state of the host material HB
Implementation Method 2
a light-emitting layer B comprising: (i) a host material HB, (ii) a thermally activated delayed fluorescence (TADF) emitter material EB
Implementation Method 3
When a voltage (and current) is applied to an organic electroluminescent device, holes and electrons are injected from an anode and a cathode, respectively, to the light-emitting layer
Data Source
AI summary
The invention relates to a an organic electroluminescent device comprising a light- emitting layer B comprising a host material HB, a first thermally activated delayed fluorescence (TADF) material EB, and an emitter material SB.