Organic EL Element with Three Light-Emitting Layers
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Solution Overview
Problem
Existing white organic electroluminescent (EL) elements have a poor balance of light emission and significant changes in chromaticity, which affect their efficiency and stability.
Innovation Solution
The organic EL element is designed with a configuration of three light-emitting layers: a dual-color red and green light-emitting layer, a blue light-emitting layer, and an additional green light-emitting layer, all using the same host material to improve luminance and reduce chromaticity changes, with specific energy level relationships and dopant concentrations to enhance energy transfer and emission balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If three light-emitting layers with different host materials are stacked to improve chromaticity balance, then chromaticity stability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent uses the same host material (compound 1) across all three light-emitting layers (red, green, and blue) to ensure homogeneous properties. This homogeneity simplifies the device structure and manufacturing process while maintaining chromaticity stability, as the consistent host material provides uniform energy transfer characteristics and electrical properties throughout the device.
Solution Approach 2:
The patent divides the white light emission function into three separate light-emitting layers, each responsible for a specific color (red, green, blue). This segmentation allows independent optimization of each layer's light-emitting materials while maintaining overall chromaticity balance, and the use of the same host material across segments simplifies the overall structure.
2Illumination intensity
If multiple light-emitting layers with optimized energy levels are used to improve light emission balance, then light emission balance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent carefully selects and adjusts the energy level parameters of the host material and light-emitting materials in each layer. The host material (compound 1) has specifically chosen HOMO and LUMO levels (-5.8 eV and -2.1 eV) that enable efficient energy transfer to all three light-emitting materials. This parameter optimization achieves balanced light emission while maintaining manufacturability.
Solution Approach 2:
The host material acts as an intermediary that facilitates energy transfer from the electrodes to the light-emitting materials in each layer. The host material's energy levels are positioned to accept electrons and holes, form excitons, and then transfer energy to the red, green, and blue light-emitting materials, enabling balanced emission without requiring precise control of multiple energy level interfaces.
3Illumination intensity
If charge barrier layers are added between light-emitting layers to improve light emission balance, then light emission balance is improved, but device complexity and driving voltage increase
Solution Approach 1:
The host material (compound 1) performs multiple functions simultaneously: it serves as the matrix for all three light-emitting layers, provides charge transport pathways, enables energy transfer to red/green/blue materials, and maintains interfacial compatibility between layers. This multi-functionality eliminates the need for separate charge barrier layers, reducing device complexity and driving voltage while achieving balanced light 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
This configuration achieves a good balance of light emission among red, green, and blue colors, maintaining stability and reducing chromaticity changes, resulting in high efficiency and low driving voltage.
Implementation Method 1
a second host material is introduced in a red-light-emitting layer so that excitation energy is transferred to a red-light-emitting material
Implementation Method 2
organic electroluminescent (EL) element that is capable of emitting white light
Data Source
AI summary
An organic EL element characterized by including a first electrode, a second electrode, and a first light-emitting layer, a second light-emitting layer, and a third light-emitting layer that are disposed between the first electrode and the second electrode, the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer each containing a host material and a light-emitting material, in which the first light-emitting layer is a light-emitting layer that emits red light and green light, the second light-emitting layer is a light-emitting layer that emits blue light, and the third light-emitting layer is a light-emitting layer that emits green light.