Organic Light-Emitting Element Sub-Layer Structure for White Light
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Solution Overview
Problem
Current current-excitation light-emitting elements using organic compounds face challenges in achieving long lifetime and efficient light emission, particularly for white light, due to issues with energy transfer and color adjustment when combining multiple organic compounds.
Innovation Solution
A light-emitting element with a two-layer structure is developed, where the first light-emitting layer is separated into two sub-layers on the anode and cathode sides, with specific weight percentages of organic compounds, and the second light-emitting layer contains a third organic compound to control carrier transportation, allowing for efficient recombination and emission of mixed color light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple organic compounds showing different emission colors are combined to achieve white light emission, then the emission color versatility is improved, but the lifetime and light-emitting efficiency deteriorate due to energy transfer issues
Solution Approach 1:
The light-emitting layer is divided into multiple sub-layers, with each sub-layer containing a specific organic compound that emits a particular color. This segmentation prevents harmful energy transfer between different compounds while maintaining overall white light emission capability through spatial separation of emission functions.
Solution Approach 2:
Each sub-layer is designed with specific local properties including tailored organic compound selection, controlled thickness, and optimized carrier injection characteristics. This allows each region to contribute optimally to the overall emission while minimizing negative interactions between different compounds.
2Adaptability or versatility
If multiple organic compounds showing different emission colors are combined to achieve white light emission, then the emission color versatility is improved, but the light-emitting efficiency deteriorates
Solution Approach 1:
By dividing the light-emitting layer into separate sub-layers for different color emissions, the patent eliminates energy transfer losses that occur when multiple compounds are mixed. Each sub-layer converts electrical energy to light independently with optimized efficiency for its specific compound.
Solution Approach 2:
The patent optimizes parameters such as sub-layer thickness, organic compound concentration, and carrier injection characteristics for each sub-layer to maximize light-emitting efficiency while maintaining the desired emission color mix for white light output.
3Adaptability or versatility
If multiple organic compounds are combined for white light emission, then the emission color versatility is improved, but the color adjustment difficulty increases due to energy transfer influence
Solution Approach 1:
The segmented sub-layer structure allows independent optimization of each color component. Color adjustment can be achieved by modifying individual sub-layer properties without affecting other color emissions, simplifying the tuning process compared to mixed-compound systems where energy transfer creates complex interdependencies.
Solution Approach 2:
Each sub-layer can be independently designed and adjusted with specific organic compounds and thicknesses to achieve desired color characteristics. This local control capability simplifies color adjustment by allowing targeted modifications in specific regions rather than system-wide changes.
4Reliability
If a two-layer structure with separated sub-layers is used, then the lifetime and efficiency are improved, but the device complexity increases
Solution Approach 1:
While the light-emitting layer is segmented into sub-layers to improve lifetime and efficiency, the overall device structure remains relatively simple with only two main layers. This segmentation is achieved within the existing layer framework rather than adding numerous separate components, thus limiting the increase in device complexity.
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 structure enables a long-lifetime light-emitting element with adjustable color emission, achieving high light-emitting efficiency and reliability, suitable for applications in display and lighting devices.
Implementation Method 1
In a basic structure of such a light-emitting element, a layer containing a light-emitting substance is interposed between a pair of electrodes. By applying voltage to this element, light emission from the light-emitting substance can be obtained.
Implementation Method 2
By applying voltage to a light-emitting element, electrons and holes are injected from a pair of electrodes into a layer containing a light-emitting substance, so that current flows therethrough. Then, by recombination of these carriers (electrons and holes), the light-emitting substance forms an excited state, and emits light when the excited state returns to a ground state.
Data Source
AI summary
A light-emitting element includes a light-emitting layer having a two-layer structure in which a first light-emitting layer containing a first light-emitting substance and a second light-emitting layer containing a second light-emitting substance, which is in contact with the first light-emitting layer, are provided between an anode and a cathode. The first light-emitting layer is separated into two layers of a layer provided on the anode side and a layer provided on the cathode side. The layer provided on the anode side contains only a first light-emitting substance, or a first organic compound of less than 50 wt % and the first light-emitting substance of 50 wt % to 100 wt %. The layer provided on the cathode side contains a second organic compound and the first light-emitting substance. The second light-emitting layer, which is provided in contact with the first light-emitting layer, contains the second light-emitting substance and a third organic compound.