Organic Electroluminescent Device Using Delayed Fluorescence
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Solution Overview
Problem
Current multiple wavelength light emitting organic electroluminescent devices face limitations in achieving high blue light intensity and efficiency, with existing structures either failing to enhance blue light emission or introducing structural complexities.
Innovation Solution
Incorporating delayed fluorescent materials as the light emitting material with the shortest wavelength, which also functions as a host for other light emitting materials, to enhance the light emission efficiency and improve color tone by emitting delayed fluorescent light, thereby increasing the quantum efficiency of blue light and allowing for a simpler device structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional fluorescent light emitting materials are used in the blue light emitting layer, then the device structure can be simplified, but the internal quantum efficiency of blue fluorescent light cannot exceed 25%, resulting in insufficient blue light intensity
Solution Approach 1:
The patent changes the emission mechanism parameter from conventional fluorescence to delayed fluorescence. By selecting a delayed fluorescent material with specific photophysical properties (longer excited state lifetime, different emission dynamics), the internal quantum efficiency is dramatically improved while maintaining the simplified single-layer structure. This parameter change in the emission mechanism resolves the contradiction between blue light intensity and energy efficiency.
2Illumination intensity
If multiple light emitting layers are used to achieve multiple wavelength emission, then color tone can be improved, but the device structure becomes complex with fixed layer arrangements
Solution Approach 1:
The delayed fluorescent material serves multiple functions simultaneously: it acts as the blue light emitting material, as the host material for green and red phosphorescent dopants, and as the medium for energy transfer. This multi-functionality eliminates the need for separate light emitting layers, achieving multiple wavelength emission (blue, green, red) in a single layer while maintaining color tone quality and reducing structural complexity.
Solution Approach 2:
The patent merges the blue fluorescent emission function with the green and red phosphorescent emission functions into a single light emitting layer. By combining these functions in one layer through energy transfer from the delayed fluorescent material to phosphorescent dopants, the device achieves multiple wavelength emission without the structural complexity of multiple separate layers.
3Ease of operation
If the green light emitting layer is positioned on the anode side as in conventional designs, then hole injection can be optimized, but design flexibility is reduced and blue light efficiency cannot be enhanced
Solution Approach 1:
The patent inverts the conventional energy transfer direction and layer arrangement logic. Instead of having the green layer on the anode side for hole injection optimization, the delayed fluorescent blue emitting material is positioned to transfer energy to green and red phosphorescent dopants within the same layer. This inversion enables blue light efficiency enhancement while achieving complete design flexibility for multiple wavelength emission.
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 use of delayed fluorescent materials significantly enhances the light emission efficiency of blue light and other wavelengths, improving the color tone and allowing for a more flexible and efficient multiple wavelength light emitting organic electroluminescent device design.
Implementation Method 1
light that has the shortest wavelength contains delayed fluorescent light
Implementation Method 2
organic electroluminescent device emitting light from the plural light emitting materials
Data Source
AI summary
An organic electroluminescent device containing a cathode, an anode, and one or more organic layers containing plural light emitting materials between the cathode and the anode, wherein the organic electroluminescent device is a multiple wavelength light emitting organic electroluminescent device emitting light from the plural light emitting materials, and which is designed so that light that has the shortest wavelength contains delayed fluorescent light can improve light emission efficiency of a short wavelength light and color tone and has a large degree of freedom in design and a simple structure.