GaN LED with Fluorescent Layer for Stable Red Light
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Solution Overview
Problem
Conventional light sources using red light emitting elements made of GaP or GaAs experience significant color shifts as temperature changes, affecting applications requiring stable chromaticity, such as displays and vehicle lighting.
Innovation Solution
A light emitting device comprising a gallium nitride-based semiconductor light emitting element with a peak emission wavelength between 420 nm and 480 nm, combined with fluorescent materials like (Sr,Ca)AlSiN3:Eu and CaAlSiN3:Eu, which convert the light to emit red light with high luminance and maintain stable chromaticity across temperature variations, utilizing a sealing member with layered fluorescent materials to optimize light absorption and emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional red light emitting elements made of GaP or GaAs are used, then the device can emit red light, but the chromaticity shifts significantly with temperature changes
Solution Approach 1:
The patent introduces a fluorescent material as an intermediary substance between the blue light emitting element and the final red light output. The fluorescent material absorbs blue light and converts it to red light through photoluminescence, acting as a mediator that decouples the temperature-dependent blue LED from the temperature-sensitive red light output, thereby stabilizing chromaticity across temperature variations
Solution Approach 2:
The patent changes the operating parameters by selecting a fluorescent material with specific photoluminescence characteristics (peak emission wavelength between 610-750 nm) that compensates for temperature-induced shifts. By carefully choosing materials with appropriate thermal characteristics and emission spectra, the system maintains stable chromaticity despite temperature changes from 25°C to 150°C
2Stability of the object's composition
If fluorescent materials are used to convert blue light to red light, then chromaticity stability is improved, but the device complexity increases
Solution Approach 1:
The patent combines the blue light emitting element and the fluorescent material into a single integrated light emitting device package. The fluorescent material is positioned in direct contact with or near the blue LED chip, allowing optical coupling without requiring separate housings or complex alignment mechanisms. This merging approach achieves stable red light output while minimizing structural complexity
Solution Approach 2:
The blue light emitting element serves multiple functions: it provides the excitation source for the fluorescent material and simultaneously contributes to the overall light output. The single blue LED chip performs dual roles as both the pump source and a component of the final emitted light, reducing the need for separate elements and simplifying the device 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
The solution provides a light source with minimal color shifts (less than 3 nm) across temperature changes from 25°C to 150°C, ensuring consistent red light emission and improved luminance efficiency, suitable for applications like displays and vehicle lighting.
Implementation Method 1
at least one fluorescent material to convert the first light to a second light having a second peak emission wavelength in a range of 610 nm or greater and 750 nm or less
Data Source
AI summary
A light emitting device includes at least one light emitting element to emit a first light having a first peak emission wavelength in a range of 420 nm to 480 nm and at least one fluorescent material to convert the first light to a second light having a second fluorescent peak wavelength in a range of 610 nm to 750 nm. The second light has chromaticity existing in an enclosed area in a CIE 1931 chromaticity diagram in which chromaticity is defined by x and y coordinates. The enclosed area is enclosed with a first straight line, a second straight line, a third straight line, and a curved line.