Organic Light-Emitting Device Triplet-Regulating Barrier Layer
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Solution Overview
Problem
Organic electroluminescent devices using delayed fluorescent materials achieve high emission efficiency but face challenges in prolonging the device's lifetime, requiring improvements in stability and longevity.
Innovation Solution
The use of a host material, a delayed fluorescent material, and a triplet-regulating compound in the light emitting layer and its adjacent layer, with specific energy requirements and concentrations, to create an organic light emitting device with a long emission lifetime and stability, where the triplet-regulating compound is present in a barrier layer in contact with the light emitting layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a delayed fluorescent material is used in the light emitting layer, then light emission efficiency is improved, but device lifetime is shortened
Solution Approach 1:
A barrier layer containing a triplet-regulating compound is introduced as an intermediary between the light emitting layer and the electrode. This barrier layer mediates the interaction by regulating triplet excitons that would otherwise degrade the delayed fluorescent material, thereby extending device lifetime while preserving high light emission efficiency.
Solution Approach 2:
The energy levels of the triplet-regulating compound in the barrier layer are specifically designed to satisfy ET1(Q) < ET1(2) < ET1(1), creating an energy gradient that directs triplet exciton flow away from the light emitting layer. This parameter optimization prevents triplet accumulation in the delayed fluorescent material, solving the lifetime problem while maintaining efficiency.
2Reliability
If the triplet-regulating compound is added to the barrier layer, then device stability is improved, but device complexity increases
Solution Approach 1:
The device is segmented into distinct functional layers: a light emitting layer containing the delayed fluorescent material and a separate barrier layer containing the triplet-regulating compound. This segmentation isolates the triplet regulation function to a dedicated layer, simplifying the overall device architecture while improving stability.
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 configuration results in an organic light emitting device with extended light emission lifetime and stability, enhancing the practicality and performance of organic electroluminescent devices.
Implementation Method 1
A delayed fluorescent material is a material which, in an excited state, after having undergone reverse intersystem crossing from an excited triplet state to an excited singlet state, emits fluorescence when returning back from the excited singlet state to a ground state thereof
Implementation Method 2
emits fluorescence when returning back from the excited singlet state to a ground state thereof
Implementation Method 3
the first organic compound, the second organic compound and the triplet-regulating compound satisfy the following requirements (a) and (b): (a) ET1(Q) < ET1(2) < ET1(1), where ET1(1) represents the lowest excited triplet energy at 77K of the first organic compound, ET1(2) represents the lowest excited triplet energy at 77K of the second organic compound, and ET1(Q) represents the lowest excited triplet energy at 77K of the triplet-regulating compound
Data Source
AI summary
An organic light emitting device having a light emitting layer that contains a first organic compound (1) and a second organic compound (2) of a delayed fluorescent material, and a barrier layer containing a triplet-regulating compound (Q) in contact with the light emitting layer, and satisfying the following formulae has a long emission lifetime and is stable. ES1 represents a lowest excited singlet energy, and ET1 represents a lowest excited triplet energy. ES1(1)>ES1(Q)>ES1(2) ET1(1)>ET1(2)>ET1(Q)