Quantum Dot LED Packaging with Segmented Phosphor Layers
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Solution Overview
Problem
Quantum dot materials used in light-emitting devices face challenges such as poor thermal stability, susceptibility to oxidation, and photo-oxidation when exposed to high-energy light, leading to reduced performance and lifespan, as well as compatibility issues with polymer matrix materials.
Innovation Solution
A chip-scale packaging light-emitting device is developed using a flip-chip LED semiconductor chip with a photoluminescent structure comprising a lower-excitation-energy-level phosphor material as an inner layer and a higher-excitation-energy-level quantum dot material as an outer layer, separated by optically transparent isolation and moisture barrier layers, to reduce thermal resistance and prevent photo-oxidation, and using different polymer matrix materials for each layer to avoid incompatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If quantum dot material is used as photoluminescent material in LED light-emitting device, then color purity and color gamut are improved, but thermal stability deteriorates due to poor heat resistance at high temperatures
Solution Approach 1:
The patent divides the photoluminescent structure into multiple layers: a first photoluminescent layer containing quantum dot material closer to the LED chip, and a second photoluminescent layer containing phosphor material farther from the LED chip. This segmentation allows the quantum dot layer to convert high-energy light while the phosphor layer handles lower-energy conversion, reducing thermal stress on the quantum dots and improving overall thermal stability while maintaining color purity.
Solution Approach 2:
The patent introduces a heat dissipation structure as an intermediary between the LED semiconductor chip and the photoluminescent layers. This heat dissipation structure acts as a thermal mediator that conducts heat away from the quantum dot material, preventing excessive temperature buildup while allowing the quantum dots to maintain their photoluminescent properties for high color purity.
2Use of energy by moving object
If quantum dot material is exposed to high-energy light for photoluminescence conversion, then light emission efficiency is improved, but photo-oxidation reaction accelerates causing luminous intensity decrease and blue shifting
Solution Approach 1:
The patent applies a protective coating on the quantum dot material before exposing it to high-energy light. This protective layer is applied in advance to prevent photo-oxidation reactions, allowing the quantum dots to maintain their luminous intensity and spectral stability while still achieving efficient photoluminescence conversion.
Solution Approach 2:
The patent creates an inert environment around the quantum dot material by using encapsulation techniques that exclude oxygen and moisture. This inert atmosphere prevents photo-oxidation reactions from occurring, maintaining the reliability and stability of luminous intensity while the quantum dots continue to efficiently convert high-energy light.
3Ease of manufacture
If quantum dot material contacts moisture or oxygen in ambient air, then manufacturing simplicity is improved, but oxidation occurs on surface causing luminous intensity to decrease
Solution Approach 1:
The patent uses thin film encapsulation layers to protect the quantum dot material from moisture and oxygen in the ambient air. These thin films provide a barrier that prevents oxidation while maintaining manufacturing simplicity, as the encapsulation can be applied using standard thin film deposition techniques during the manufacturing process.
Solution Approach 2:
The patent employs composite material structures that combine quantum dot material with protective matrix materials or surface treatments. This composite approach allows the quantum dots to maintain their photoluminescent properties while the composite structure provides resistance to oxidation from moisture and oxygen, ensuring long-term luminous intensity stability.
4Device complexity
If single polymer matrix material is used for both phosphor and quantum dot layers, then device complexity is reduced, but material incompatibility occurs between different photoluminescent materials
Solution Approach 1:
The patent segments the photoluminescent structure into multiple layers, each with its own optimized polymer matrix material. The first layer uses a polymer matrix suitable for quantum dot material, while the second layer uses a different polymer matrix optimized for phosphor material. This segmentation resolves material incompatibility issues while maintaining manageable device complexity through a systematic layered architecture.
Solution Approach 2:
The patent applies the principle of local quality by selecting different polymer matrix materials for different regions (layers) of the photoluminescent structure. Each layer's polymer matrix is locally optimized for its specific photoluminescent material, ensuring maximum compatibility and performance. The first layer uses a polymer matrix tailored for quantum dots, while the second layer uses a polymer matrix tailored for phosphors, with each local region having the appropriate material properties.
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 reduces thermal degradation and photo-oxidation of quantum dot materials, enhancing their stability and performance by lowering operating temperatures and preventing moisture and oxygen exposure, while also improving light extraction efficiency and compatibility between polymer matrix materials.
Implementation Method 1
While being irradiated by a high-energy-level light, due to Quantum confinement effect, a quantum dot material can convert a portion of incident light into another lower-energy-level visible light.
Implementation Method 2
a photoluminescent structure disposed on a chip-upper surface of the flip-chip LED semiconductor chip, wherein the photoluminescent structure includes a first photoluminescent layer, an optically transparent isolation layer, a second photoluminescent layer
Implementation Method 3
the light-emitting device using the quantum dot material should have a good moisture barrier protection against penetration of external water vapor and oxygen into and coming in contact with the quantum dot material
Implementation Method 4
a flip-chip LED semiconductor chip configured for providing a primary light
Data Source
AI summary
A light-emitting device includes a flip-chip LED semiconductor chip to provide a primary light, a photoluminescent (PL) structure disposed on the LED semiconductor chip and a moisture-barrier reflective structure covering a chip-edge surface of the LED semiconductor chip and a photoluminescent-side surface of the PL structure. The sequentially stacked PL structure includes a first PL layer, a transparent isolation layer, a second PL layer and a transparent moisture barrier layer. For example, the LED semiconductor chip emits a blue light, the first PL layer includes a red phosphor material, and the second PL layer includes a green quantum dot (QD) material. Therefore, the red phosphor material of the first PL layer can convert a portion of the higher-energy-level blue light into a lower-energy-level converted red light, so as to reduce an intensity of an unconverted portion of the blue light reaching the green QD material within the second PL layer.