Organic Electroluminescence Display Device with Ultra-Thin Emission Layer
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Solution Overview
Problem
Existing organic electroluminescence display devices face challenges in reducing material costs while maintaining efficiency, particularly due to the thickness and composition of emission layers, which affect the overall thickness and performance of the devices.
Innovation Solution
The organic electroluminescence display device incorporates a light-emitting unit with a second emission layer of ultra-thin thickness (about 1 nm or less) that includes a host and dopants, configured to emit light mixed with blue light to produce white light, along with specific energy level differences between emission layers to enhance charge balance and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the emission layer thickness is increased to maintain efficiency, then the device efficiency is improved, but the device thickness increases and material costs increase
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the second emission layer to be 1 nm or less, and adjusting the energy level differences between emission layers (HOMO difference ≥0.3 eV, LUMO difference ≥0.15 eV). This allows achieving efficient light emission with ultra-thin layers, resolving the contradiction between maintaining efficiency and reducing device thickness.
Solution Approach 2:
The patent implements local quality by creating different emission layers with specific characteristics: the second emission layer has ultra-thin thickness (≤1 nm) and specific host materials, while other layers have different thicknesses and compositions. This localized optimization allows the device to achieve overall efficiency while maintaining thin profile in critical regions.
2Reliability
If the emission layer thickness is increased to ensure proper charge injection and emission zone formation, then the device efficiency is improved, but the material cost increases
Solution Approach 1:
The patent changes the thickness parameter of the second emission layer to ultra-thin (≤1 nm) and optimizes energy level parameters (HOMO and LUMO differences) to ensure proper charge injection and emission zone formation. This allows achieving reliable charge injection with minimal material usage, reducing material cost while maintaining efficiency.
Solution Approach 2:
The patent applies partial action by using a very thin second emission layer (≤1 nm) that is sufficient for its specific function of emitting white light when mixed with blue light, without requiring excessive thickness for charge injection. The charge injection is optimized through energy level alignment rather than increased thickness, reducing material consumption.
3Reliability
If multiple emission layers with different hosts are used to achieve white light emission, then the device efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent segments the light-emitting unit into multiple sub-light-emitting units (first, second, and third) with different emission layers. The second sub-light-emitting unit has an ultra-thin emission layer (≤1 nm) that emits white light when mixed with blue light from the other layers. This segmentation allows efficient white light emission through coordinated operation of simpler individual layers.
Solution Approach 2:
The patent uses composite materials approach by combining different host materials in different emission layers: the first and second emission layers use a first host, while the third emission layer uses a second host. This composite structure enables efficient white light emission through spectral combination while managing complexity through systematic material selection.
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 reduces material costs, maintains efficiency, and aligns with the trend of thinner display devices, while ensuring effective hole and electron injection and emission zone formation, thus achieving excellent efficiency and compliance with display device thinning requirements.
Implementation Method 1
The organic electroluminescence display device may generate light using a principle, in which holes and electrons respectively injected from a first electrode and a second electrode are recombined in an emission layer to emit light, wherein light is emitted when excitons formed by the recombination of the injected electrons and holes drop from an excited state to a ground state.
Data Source
AI summary
An organic electroluminescence display device includes a first electrode, a second electrode on the first electrode, and a light-emitting unit between the first electrode and the second electrode, the light-emitting unit including a first sub-light-emitting unit on the first electrode and including a first emission layer, a first charge generation layer on the first sub-light-emitting unit, a second sub-light-emitting unit on the first charge generation layer and including a second emission layer, a second charge generation layer on the second sub-light-emitting unit, and a third sub-light-emitting unit on the second charge generation layer and including a third emission layer, wherein each of the first emission layer and the second emission layer includes a first host, the third emission layer includes a second host different from the first host, and a thickness of the second emission layer is 1.0 nm or less.