Organic Electroluminescent Device with Segmented Luminescent Layer
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Solution Overview
Problem
Conventional organic electroluminescent devices have unsatisfactory luminous efficiency and chromaticity, particularly in achieving high luminance and desired chromaticity at low voltage, due to the limitations of blue light intensity and the need to adjust green and red phosphorescence intensities.
Innovation Solution
An organic electroluminescent device with multiple organic compound layers, including a luminescent layer containing a host material and multiple luminescent materials, including at least one phosphorescent material, arranged in specific regions within the thickness direction to optimize charge transfer and emission wavelengths, thereby enhancing luminous efficiency and chromaticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If blue phosphorescent material is used to improve chromaticity, then chromaticity is improved, but luminous efficiency decreases due to low blue light intensity
Solution Approach 1:
The patent applies local quality by creating distinct regions within the luminescent layer with different material compositions. Specifically, a first luminescent layer contains blue phosphorescent material for chromaticity, while a second luminescent layer contains green and red phosphorescent materials for efficiency. This spatial differentiation allows each region to optimize for its specific function, resolving the contradiction between chromaticity and luminous efficiency.
Solution Approach 2:
The luminescent layer is segmented into multiple sub-layers with different functional characteristics. The first luminescent layer (with blue phosphor) and second luminescent layer (with green and red phosphors) are separated into distinct regions, allowing independent optimization of each segment's properties without compromising the overall device performance.
2Illumination intensity
If green and red phosphorescence intensities are adjusted to achieve desired chromaticity, then chromaticity is improved, but luminous efficiency decreases
Solution Approach 1:
The patent places green and red phosphorescent materials in a dedicated second luminescent layer, allowing their intensities to be optimized locally without affecting the blue region. This spatial separation enables independent control of each color component's intensity, achieving desired chromaticity while maintaining high luminous efficiency in each region.
3Device complexity
If multiple luminescent materials are mixed in the same layer, then device complexity is reduced, but charge transfer barriers increase and luminous efficiency decreases
Solution Approach 1:
Instead of mixing all luminescent materials in a single layer, the patent segments them into multiple luminescent layers with distinct material compositions. This segmentation reduces charge transfer barriers between different material types while maintaining a relatively simple overall device structure, thereby preserving high luminous efficiency.
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 device achieves superior luminous efficiency, brightness, and chromaticity by optimizing the distribution and concentration of luminescent materials, reducing charge transfer barriers and improving charge-transporting properties, resulting in improved external quantum efficiency and reduced power consumption.
Implementation Method 1
Use of a phosphorescent material, which has higher luminous efficiency than a fluorescent material, is preferable for reduction of operation voltage and improvement in luminance
Implementation Method 2
emit light with the excitons generated by recombination of the electrons injected from a cathode and holes injected from an anode in the luminescent layer
Data Source
AI summary
The invention provides an organic electroluminescent device having one or more organic compound layers between a pair of electrodes, the one or more organic compound layers including at least a luminescent layer, wherein a host material and at least two different luminescent materials including at least one phosphorescent material are contained in the same luminescent layer, and the luminescent layer has a region containing the host material and one luminescent material and a region containing the host material and at least two luminescent materials in the thickness direction of the luminescent layer.