Quantum Dot Matrix With Core-Shell Coatings For Thermal Quenching
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Solution Overview
Problem
Quantum dots used in lighting applications face challenges with low quantum efficiency, thermal quenching, and stability due to sensitivity to surface environments and lattice mismatch issues when growing shells, making it difficult to achieve high performance in simple spherical or rod shape structures.
Innovation Solution
A luminescent nano particle based material with a matrix of interconnected coated semiconductor nano particles, where the nano particles are coated with a first material like CdS and a second material like ZnS, forming a core-multi shell structure that reduces thermal quenching and enhances quantum yield by maintaining the nano particles at a distance from each other within the matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If quantum dots are used as phosphor materials for lighting applications, then narrow emission band and tunable emission wavelength are achieved, but low quantum efficiency and thermal quenching occur due to sensitivity to surface environments
Solution Approach 1:
The patent implements a nested core-shell structure where semiconductor quantum dots (core) are enclosed within a first shell material, which is further enclosed within a second shell material. This nested configuration protects the quantum dots from surface environment sensitivity while maintaining their optical properties, thereby improving quantum efficiency and reducing thermal quenching.
Solution Approach 2:
The patent uses composite materials by combining different shell materials (first shell and second shell) with the quantum dot core. The first shell is selected from specific semiconductor materials while the second shell is selected from different materials, creating a composite structure that enhances stability and quantum efficiency while preserving the narrow emission band characteristics.
2Reliability
If additional shells are grown on quantum dots to improve quantum efficiency and avoid concentration and temperature quenching, then quantum yield increases, but lattice mismatch and built in stresses make synthesis difficult
Solution Approach 1:
The patent systematically varies material parameters by selecting specific first and second shell materials from defined groups, controlling shell thickness ratios, and adjusting composition gradients. These parameter changes optimize quantum yield while managing lattice mismatch and synthesis complexity through controlled material selection and structural design.
3Use of energy by moving object
If thick shells of semiconductor materials are grown on core quantum dots to improve light absorbance and reduce concentration quenching, then absorption efficiency increases, but large volume ratio and rod or multi-pods shape are required to maintain minimum lattice mismatch
Solution Approach 1:
The patent applies local quality by creating spatially varying shell thicknesses and compositions - the first shell has specific thickness and material properties optimized for lattice matching, while the second shell provides additional protection and optical enhancement. This localized optimization allows thick effective shells for improved absorbance while maintaining spherical morphology and minimizing lattice mismatch.
4Reliability
If ZnS is used for surface passivation to achieve high quantum efficiency and stability, then quantum yield improves, but ZnS is more stable when growing on spherical surface while other materials require rod or multi-pods shape
Solution Approach 1:
The patent resolves the shape conflict by introducing a multi-layer dimensional structure - the first shell serves as an intermediate layer between the quantum dot core and the ZnS second shell. This additional dimensional layer allows ZnS to grow stably on a spherical surface while the first shell accommodates the specific growth requirements of other materials, effectively decoupling the shape constraints of different materials.
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 coated matrix structure achieves high quantum efficiency, reduced thermal quenching, and improved stability, with quantum yields exceeding those of uncoated nano particles and coated particles, while maintaining the nano particles at a distance to minimize reabsorption losses.
Implementation Method 1
a plurality of first quantum dots for generating wavelength-converted light by converting wavelength of light from the light emitting source
Data Source
AI summary
The invention provides a luminescent nano particles based luminescent material comprising a matrix of interconnected coated luminescent nano particles, wherein for instance wherein the luminescent nano particles comprise CdSe, wherein the luminescent nano particles comprise a coating of CdS and wherein the matrix comprises a coating comprising ZnS. The luminescent material according may have a quantum efficiency of at least 80% at 25° C., and having a quench of quantum efficiency of at maximum 20% at 100° C. compared to the quantum efficiency at 25° C.