Light-Emitting Element With Luminescence-Assisting Layers
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Solution Overview
Problem
Organic electroluminescent elements formed through liquid phase processes exhibit rapid luminance decrease and color changes due to variations in luminescent layer thickness, leading to reduced efficiency and shortened lifespan.
Innovation Solution
Incorporating a luminescent layer with first and second luminescence-assisting layers made of high-molecular-weight materials, similar to the host material, to prevent exciton deactivation and maintain optimal optical path length, thereby stabilizing the luminescent region and enhancing luminous efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the thickness of the luminescent layer is increased, then the optical path length is increased, but the position and width of the luminescent region are changed causing color change
Solution Approach 1:
The invention divides the luminescent layer into multiple sub-layers (first luminescent sub-layer, second luminescent sub-layer, third luminescent sub-layer) with different thicknesses and luminescent materials. This segmentation allows each sub-layer to contribute differently to the overall luminescence, maintaining stable color output while achieving sufficient optical path length for efficient luminescence.
2Stability of the object's composition
If the thickness of the luminescent layer is reduced, then the luminescent region position and width are stabilized, but excitons reach adjacent layers causing deactivation and reduced luminous efficiency
Solution Approach 1:
The invention introduces blocking layers (hole blocking layer and electron blocking layer) as intermediaries between the luminescent layer and adjacent transport layers. These blocking layers prevent excitons from reaching and being deactivated in adjacent layers, thereby maintaining high luminous efficiency while allowing the luminescent layer to have reduced thickness for stable color output.
3Stability of the object's composition
If the thickness of the luminescent layer is merely reduced, then the luminescent region is stabilized, but the optical path length becomes insufficient reducing luminance
Solution Approach 1:
The invention applies local quality by creating sub-layers with different characteristics - the first luminescent sub-layer has greater thickness for sufficient optical path length, while the second and third luminescent sub-layers have smaller thicknesses for stable luminescent region. Each sub-layer is positioned strategically to optimize both luminance and color stability.
4Ease of manufacture
If liquid application is used to form the luminescent layer, then manufacturing is simplified and material usage is reduced, but rapid luminance decrease and color change occur
Solution Approach 1:
The invention uses composite materials by combining multiple luminescent materials with different characteristics (fluorescent and phosphorescent materials) in different sub-layers. This composite approach maintains the ease of liquid application manufacturing while achieving stable luminance and color by distributing the luminescent function across multiple materials that compensate for each other's deficiencies.
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 effectively prevents luminescent color change and enhances luminous efficiency while extending the lifespan of the light-emitting element by maintaining the luminescent region's stability and optimal optical path length.
Implementation Method 1
a luminescent layer which contains a luminescent material that emits light by applying a current between the anode and the cathode
Implementation Method 2
a host material that helps the luminescent layer emit light
Implementation Method 3
The first luminescence-assisting layer has a function of preventing the excitons from being deactivated
Data Source
AI summary
A light-emitting element includes an anode, a cathode, a luminescent layer disposed between the anode and the cathode and containing a host material, a first luminescence-assisting layer disposed in contact with the luminescent layer between the anode and the luminescent layer and containing a first luminescence-assisting material having characteristics the same as or similar to the host material, and a second luminescence-assisting layer disposed in contact with the luminescent layer between the cathode and the luminescent layer and containing a second luminescence-assisting material having characteristics the same as or similar to the host material. The luminescent layer and the first luminescence-assisting layer each contain a high-molecular-weight material.