Light-Emitting Element Delayed Fluorescence via Triplet-Triplet Annihilation
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Solution Overview
Problem
Conventional light-emitting elements with fluorescent compounds face challenges in achieving high efficiency due to low conversion of triplet excitons into singlet excitons, limiting their emission efficiency and proportion of delayed fluorescence.
Innovation Solution
Incorporating organic compounds with specific structural features, such as tetracene or anthracene skeletons, that facilitate energy transfer through the Förster mechanism, increasing the probability of triplet-triplet annihilation (TTA) to convert triplet excitons into singlet excitons, thereby enhancing the proportion of delayed fluorescence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fluorescent compound is used in a light-emitting element, then the element can be formed with a stable compound, but the emission efficiency is limited due to low conversion of triplet excitons into singlet excitons
Solution Approach 1:
The patent changes the energy level parameters of the host material by selecting compounds with specific T1 and Tn level configurations. The key parameter change is ensuring that the energy difference between T1 and Tn levels is less than the sum of T1 level and 0.6 eV, which enables efficient TTA and improves emission efficiency while maintaining fluorescent compound stability.
Solution Approach 2:
The host material acts as an intermediary that facilitates energy transfer from triplet excitons to singlet excitons through TTA. The host material's Tn levels serve as intermediate energy states that enable the conversion process, allowing triplet excitons to be transformed into singlet excitons that can then transfer energy to the fluorescent compound for light emission.
2Device complexity
If conventional host materials are used, then the light-emitting element structure is simple, but the proportion of delayed fluorescence to total light emitted is low (approximately 10% or less)
Solution Approach 1:
The patent modifies the energy level parameters of the host material, specifically selecting compounds where the difference between T1 and Tn levels is less than the sum of T1 level and 0.6 eV. This parameter change increases the probability of TTA, thereby increasing the proportion of delayed fluorescence to at least 5% or more, potentially reaching higher values while maintaining structural simplicity.
3Loss of energy
If organic compounds with specific structural features (tetracene or anthracene skeletons) are incorporated, then the probability of triplet-triplet annihilation increases, but the device structure becomes more complex
Solution Approach 1:
The patent changes the molecular structure parameters of the host material by incorporating specific skeletons (tetracene or anthracene). These structural features inherently provide the desired energy level characteristics (T1-Tn difference less than T1 + 0.6 eV), enabling efficient TTA and high delayed fluorescence proportion while the complexity is managed through targeted molecular design rather than complex 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
This approach significantly improves the emission efficiency of light-emitting elements by increasing the proportion of delayed fluorescence to at least 5% or more, leading to higher efficiency and energy-saving capabilities.
Implementation Method 1
Incorporating organic compounds with specific structural features, such as tetracene or anthracene skeletons, that facilitate energy transfer through the Förster mechanism, increasing the probability of triplet-triplet annihilation (TTA) to convert triplet excitons into singlet excitons
Implementation Method 2
light emission from the singlet excited state is referred to as fluorescence
Implementation Method 3
research and development of light-emitting elements using electroluminescence (EL) have been actively conducted
Data Source
AI summary
A light-emitting element that contains a fluorescent compound, which has high efficiency is provided. A light-emitting element in which the proportion of delayed fluorescence to the total light emitted from the light-emitting element is higher than that in a conventional light-emitting element is provided. Emission efficiency of the light-emitting element containing a fluorescent compound can be improved by increasing the probability of TTA caused by an organic compound in an EL layer, converting energy of triplet excitons, which does not contribute to light emission, into energy of singlet excitons, and making the fluorescent compound emit light by energy transfer of the singlet excitons.