Light-Emitting Device With Low-Index EL and Quantum-Dot Conversion
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Solution Overview
Problem
Low outcoupling efficiency and trade-off relationship between refractive index and carrier-transport property in organic EL devices, leading to reduced device efficiency and reliability.
Innovation Solution
Incorporation of a layer with a refractive index lower than or equal to 1.75 for 467-nm wavelength light in the EL layer, combined with a color conversion layer using quantum dots to enhance light emission efficiency and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a layer with low refractive index is introduced in the EL layer to reduce reflection loss, then outcoupling efficiency is improved, but carrier-transport property and device reliability deteriorate
Solution Approach 1:
The patent employs composite materials by combining organic compounds with different refractive indices and carrier-transport properties in the EL layer. Specifically, it uses a host material and a guest material (such as Alq3 and BCP combinations) to create a layered structure where each material contributes its advantageous properties: low refractive index for reduced reflection loss and high carrier-transport capability for maintained device reliability.
Solution Approach 2:
The patent applies local quality by creating distinct functional zones within the EL layer. Different regions are designed with specific refractive indices and carrier-transport characteristics tailored to their local functions: some regions optimized for light extraction while others optimized for carrier transport, thereby simultaneously achieving high outcoupling efficiency and maintained reliability.
2Loss of energy
If a layer with low refractive index is introduced in the EL layer to reduce reflection loss, then outcoupling efficiency is improved, but device efficiency deteriorates
Solution Approach 1:
The patent uses composite material systems in the EL layer that balance optical and electrical functions. The combination of materials with different refractive indices and carrier mobilities ensures that while reflection loss is reduced, the overall device efficiency is maintained through optimized carrier injection, transport, and recombination processes.
Solution Approach 2:
The patent systematically varies key parameters including refractive index, carrier mobility, and energy levels of the materials in the EL layer to achieve optimal performance. By adjusting these parameters in a coordinated manner, the patent minimizes reflection loss while maintaining high device efficiency through controlled carrier dynamics.
3Illumination intensity
If organic compounds with many unsaturated bonds are used to achieve high refractive index, then light emission intensity is improved, but outcoupling efficiency deteriorates
Solution Approach 1:
The patent combines materials with high refractive indices (for intense light emission) and low refractive indices (for efficient outcoupling) in a composite EL layer structure. This allows the system to achieve both high illumination intensity and high outcoupling efficiency by leveraging the complementary optical properties of different materials in the composite structure.
Solution Approach 2:
The patent resolves the contradiction by moving from a single-material approach to a multi-layer composite approach, adding the dimension of material heterogeneity. This allows independent optimization of optical emission properties and optical extraction properties in different layers or regions of the EL structure.
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
Improves light-emitting apparatus efficiency, extends device lifetime, reduces power consumption, and enhances reliability by optimizing refractive index and using quantum dots for high-color-purity light emission.
Implementation Method 1
the attenuation due to reflection which is caused by a difference in refractive index between adjacent layers
Implementation Method 2
the attenuation due to reflection which is caused by a difference in refractive index between adjacent layers
Implementation Method 3
A color conversion method is a method in which a photoluminescent substance is irradiated with light from light-emitting devices to convert the light into light of desired colors
Data Source
AI summary
A light-emitting apparatus with low power consumption is provided. A light-emitting apparatus including a first light-emitting device and a first color conversion layer. The first light-emitting device includes an anode, a cathode, and an EL layer positioned between the anode and the cathode. The EL layer includes a layer including a material with a refractive index lower than or equal to 1.75 at 467 nm. The first color conversion layer includes a first substance capable of emission by absorbing light. Light emitted from the first light-emitting device enters the first color conversion layer.