Light-emitting Element Exciplex Host Material Efficiency
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Solution Overview
Problem
Current light-emitting elements using thermally activated delayed fluorescent emitters face challenges in achieving high emission efficiency due to inefficient generation of singlet excited states and energy transfer, particularly in converting triplet excited states into light emission.
Innovation Solution
A light-emitting element is designed with an EL layer that forms an exciplex, utilizing a host material composed of two organic compounds to efficiently convert triplet excitons into singlet excitons and transfer energy to a fluorescent material for enhanced emission efficiency, with specific structural and energetic conditions to optimize energy transfer and fluorescence quantum yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thermally activated delayed fluorescent emitter is used to convert triplet excited states into light emission, then emission efficiency can be improved, but the generation of singlet excited states remains inefficient
Solution Approach 1:
The patent introduces a fluorescent compound as an intermediary substance that receives energy from the thermally activated delayed fluorescent emitter and converts it to light emission. This mediator enables efficient energy transfer from triplet excited states to singlet excited states, resolving the contradiction between improving emission efficiency and maintaining efficient singlet excited state generation.
Solution Approach 2:
The patent modifies the energy level parameters of the fluorescent compound to match the triplet excited state energy of the thermally activated delayed fluorescent emitter. By adjusting the energy gap and other parameters, the system achieves efficient energy transfer and conversion of triplet excited states into light emission while maintaining high singlet excited state generation efficiency.
2Loss of energy
If the fluorescent compound is placed close to the thermally activated delayed fluorescent emitter for efficient energy transfer, then emission efficiency increases, but the structural design becomes more complex
Solution Approach 1:
The patent merges the thermally activated delayed fluorescent emitter and the fluorescent compound into a single integrated light-emitting layer structure. This combination allows efficient energy transfer while simplifying the overall device structure, as the two components work together within the same layer rather than requiring separate complex assemblies.
Solution Approach 2:
The patent employs a composite material system consisting of the thermally activated delayed fluorescent emitter and the fluorescent compound combined in a specific ratio and matrix. This composite approach enables efficient energy transfer through the interaction of different materials while maintaining a relatively simple overall structure that can be manufactured using standard techniques.
3Illumination intensity
If a fluorescent compound with high fluorescence quantum yield is used, then light emission efficiency improves, but the conversion of triplet excited states into singlet excited states becomes less efficient
Solution Approach 1:
The patent carefully adjusts the energy level parameters and other characteristics of the fluorescent compound to optimize both light emission intensity and triplet excited state conversion efficiency. By selecting compounds with specific energy gaps and other parameters, the system achieves high performance in both aspects without compromise.
Solution Approach 2:
The patent applies different functional characteristics to different parts of the light-emitting system: the thermally activated delayed fluorescent emitter is optimized for triplet excited state conversion, while the fluorescent compound is optimized for light emission. This division of functional quality allows each component to excel at its specific task, resolving the contradiction between conversion efficiency and emission intensity.
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 a light-emitting element with high emission efficiency, low power consumption, and a novel display device capable of efficient energy transfer and light emission, overcoming previous limitations in triplet excited state conversion and emission efficiency.
Implementation Method 1
a singlet excited state is generated from a triplet excited state by reverse intersystem crossing
Implementation Method 2
singlet excitation energy of the thermally activated delayed fluorescent emitter is transferred to the fluorescent compound
Implementation Method 3
Light emission from the singlet-excited state is referred to as fluorescence
Data Source
AI summary
A light-emitting element containing a fluorescent material and having high emission efficiency is provided. The light-emitting element contains the fluorescent material and a host material. The host material contains a first organic compound and a second organic compound. The first organic compound and the second organic compound can form an exciplex. The minimum value of a distance between centroids of the fluorescent material and at least one of the first organic compound and the second organic compound is 0.7 nm or more and 5 nm or less.