Quantum Dot and Phosphor Down-Conversion for White LED Color Rendering
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Solution Overview
Problem
Existing solid-state white light emitting devices using only inorganic phosphors for down-conversion of short wavelength light are limited in spectral efficiency and result in white light with high correlated color temperature and poor color rendering properties, especially in the red region.
Innovation Solution
A method utilizing a combination of quantum dot and phosphor materials to down-convert short wavelength light, where quantum dots absorb and reemit light as long wavelength light, and phosphors absorb and reemit as mid wavelength light, producing visible light with a chromaticity near the blackbody locus and a color rendering index greater than 80.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If only inorganic phosphors are used for down-conversion, then the device complexity is low, but the color rendering index and spectral power distribution are poor
Solution Approach 1:
The patent combines quantum dot materials with inorganic phosphors to create a composite down-conversion system. The quantum dots convert short wavelength light to mid-wavelength light, while the phosphors convert short wavelength light to long wavelength light, producing a combined spectrum that achieves high color rendering index (greater than 80) and improved spectral power distribution, resolving the contradiction between simple device structure and poor color rendering.
2Use of energy by moving object
If short wavelength LEDs are used with phosphor down-conversion, then the luminous efficacy is improved, but the correlated color temperature becomes high and color rendering is poor
Solution Approach 1:
The down-conversion process is segmented into two distinct pathways: quantum dots converting short wavelength light to mid-wavelength light, and phosphors converting short wavelength light to long wavelength light. This segmentation allows independent optimization of each conversion pathway to achieve the desired correlated color temperature and color rendering index while maintaining high luminous efficacy.
Solution Approach 2:
The patent changes the spectral parameters by introducing quantum dots with specific emission wavelengths to fill spectral gaps. By adjusting the quantum dot size and composition, the emission spectrum can be tuned to achieve optimal correlated color temperature and color rendering while preserving the high efficiency of short wavelength LED excitation.
3Manufacturing precision
If quantum dot and phosphor materials are combined for down-conversion, then the color rendering index is improved, but the device complexity increases
Solution Approach 1:
The patent merges quantum dot materials and phosphor materials into a unified down-conversion package that is optically coupled to a single short wavelength LED. This combining approach achieves high color rendering index (greater than 80) and improved spectral power distribution while maintaining a relatively simple overall device structure, as both materials are excited by the same LED source and work together to produce the desired output spectrum.
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 approach enhances the luminous efficacy and color rendering index of the light source, improving its spectral power distribution and making it more suitable for general illumination applications by producing a nearly continuous spectrum with improved chromaticity and reduced correlated color temperature.
Implementation Method 1
The quantum dot material is irradiated with at least a portion of the short wavelength light such that a first fraction of the short wavelength light is absorbed and reemitted by the quantum dot material as long wavelength light
Implementation Method 2
The phosphor material is irradiated with at least a portion of the short wavelength light such that a second fraction of the short wavelength light is absorbed and reemitted by the phosphor material as mid wavelength light
Data Source
AI summary
A broad bandwidth light source including: a solid state light emitting device that generates short wavelength light; and quantum dot material and phosphor material that are each irradiated by some of the short wavelength light. The short wavelength light has a spectrum with a first peak wavelength shorter than about 500 nm. The quantum dot material absorbs some of the short wavelength light and reemits it as long wavelength light having a spectrum with a second peak wavelength longer than about 600 nm. The phosphor material absorbs some of the short wavelength light and reemits it as mid wavelength light having a spectrum with a peak wavelength between the first and second peak wavelength. The light source is configured such that some of each light (short, mid, and long wavelength) is emitted coincidentally as a light having a chromaticity value near the blackbody locus and a color rendering index greater than 80.