TADF-TTA Dual-Layer Light Emitting Element for Efficiency and Service Life
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Solution Overview
Problem
There is a persistent demand for organic electroluminescence elements with low driving voltage, high luminous efficiency, and long service life in display devices, which existing technologies have not adequately addressed.
Innovation Solution
A light emitting element comprising a first emission layer with a (1-1)-th compound and a second emission layer with a (2-1)-th compound, where the (2-1)-th compound has a lowest excited triplet energy level of 1.5 eV to 2.1 eV, configured to emit fluorescence through thermally activated delayed fluorescence (TADF) and triplet-triplet annihilation (TTA), enhancing luminous efficiency and service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional organic electroluminescence materials are used, then the display device can achieve basic light emission, but the luminous efficiency and service life remain insufficient
Solution Approach 1:
The patent employs a composite emission layer structure comprising a first emission layer with TADF material and a second emission layer with TTA material. This composite structure enables synergistic utilization of both delayed fluorescence and triplet-triplet annihilation mechanisms, achieving high luminous efficiency while extending service life through optimized energy utilization and reduced exciton quenching
Solution Approach 2:
The patent optimizes the triplet energy level parameter of the TTA material to be within 1.5 eV to 2.1 eV, and adjusts the thickness ratio between the first and second emission layers. These parameter optimizations enable efficient energy transfer from the TADF layer to the TTA layer, maximizing luminous efficiency while maintaining device stability and service life
2Productivity
If phosphorescence emission or fluorescence with triplet-triplet annihilation is used, then luminous efficiency can be improved, but the device complexity increases
Solution Approach 1:
The emission layer is segmented into two functional sub-layers: a first emission layer containing TADF material for generating triplet excitons, and a second emission layer containing TTA material for converting triplet excitons to singlet excitons. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall system simplicity
Solution Approach 2:
The dual-layer emission structure serves multiple functions: the first layer generates triplet excitons through TADF, the second layer converts triplet to singlet excitons through TTA, and the interface between layers facilitates efficient energy transfer. This multi-functionality achieves high luminous efficiency without proportionally increasing device complexity
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 proposed configuration improves luminous efficiency and service life of the light emitting element, resulting in enhanced display quality.
Implementation Method 1
configured to emit fluorescence through thermally activated delayed fluorescence (TADF)
Implementation Method 2
configured to emit fluorescence through thermally activated delayed fluorescence (TADF) and triplet-triplet annihilation (TTA)
Data Source
AI summary
Embodiments provide a light emitting element and a display device that includes the light emitting element. The light emitting element includes a first electrode, a first emission layer disposed on the first electrode and including a (1-1)-th compound, a second emission layer disposed on the first emission layer and including a (2-1)-th compound, and a second electrode disposed on the second emission layer, wherein the (2-1)-th compound has a lowest excited triplet energy level (T1) in a range of about 1.5 eV to about 2.1 eV. The (1-1)-th compound is represented by Formula 1, the (2-1)-th compound is represented by Formula 2, and Formula 1 and Formula 2 are each described in the specification.