Semiconductor Light Emitting Devices with Red Phosphors for Color Rendering
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Solution Overview
Problem
Conventional semiconductor light emitting devices often face a tradeoff between achieving high luminous flux and maintaining good color rendering properties, as the addition of luminescent materials to improve color rendering can result in decreased luminous flux due to the need for wide wavelength coverage that aligns with human eye sensitivity.
Innovation Solution
Incorporating a recipient luminophoric medium with a specific composition of green, yellow, and red phosphors, including a (Ca1-x-ySrxEu2+y)SiAlN3 red phosphor, a gallium-substituted YAG:Ce or LuAG:Ce green phosphor, and optionally a YAG:Ce yellow phosphor, to down-convert blue light emitted by a blue LED, optimizing the ratio of non-red to red phosphor particles to achieve high CRI Ra and R9 values while maintaining luminous flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If luminescent materials are added to improve color rendering properties, then CRI Ra and R9 values are improved, but luminous flux decreases
Solution Approach 1:
The patent optimizes the wavelength peak positions of phosphors (green: 525-550nm, yellow: 550-580nm, red: 610-650nm) and their relative ratios to achieve high CRI Ra (>90) and R9 (>85) while maintaining high luminous flux. This parameter optimization resolves the contradiction by finding the optimal balance point where color rendering is improved without excessive luminous flux loss
Solution Approach 2:
The patent uses a composite phosphor system combining green phosphor (gallium-substituted YAG:Ce or LuAG:Ce), yellow phosphor (YAG:Ce), and red phosphor ((Ca1-x-ySrxEu2+y)SiAlN3) with a blue LED to create a multi-wavelength light source. This composite approach enables broad spectrum coverage for excellent color rendering while maintaining high overall luminous flux through synergistic combination of phosphors
2Measurement precision
If wide wavelength coverage is achieved to improve color rendering, then CRI Ra and R9 values are improved, but luminous flux decreases
Solution Approach 1:
The patent carefully controls the wavelength peaks of individual phosphors (green: 525-550nm, yellow: 550-580nm, red: 610-650nm) and their relative intensities to achieve broad but efficient spectral coverage. This optimized parameter selection ensures wide wavelength coverage for high CRI Ra (>90) and R9 (>85) while minimizing luminous flux loss by aligning phosphor emission with the human eye sensitivity curve
Solution Approach 2:
The patent enhances specific wavelength regions by selecting phosphors with targeted emission peaks that complement each other. The green phosphor fills the 525-550nm gap, yellow phosphor covers 550-580nm, and red phosphor provides 610-650nm coverage, creating localized spectral enhancements that collectively achieve broad coverage with high efficiency
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 enables semiconductor light emitting devices to produce white light with a correlated color temperature between 2500K and 4500K, achieving CRI Ra values greater than 90 and R9 values greater than 85, thereby improving color rendering while maintaining or enhancing luminous flux.
Implementation Method 1
a light emitting diode that emits light having a dominant wavelength in the blue color range
Implementation Method 2
a recipient luminophoric medium that is configured to down-convert at least some of the light emitted by the LED
Data Source
AI summary
A light emitting device includes a light emitting diode (“LED”) that emits light having a dominant wavelength in the blue color range, and a recipient luminophoric medium that is configured to down-convert at least some of the light emitted by the LED. The recipient luminophoric medium includes a green phosphor that down-converts the radiation emitted by the LED to radiation having a peak wavelength that is between about 525 nanometers and about 550 nanometers, a yellow phosphor having a wavelength peak that is between about 550 nanometers and about 580 nanometers, and a red (Ca1-x-ySrxEu2+y)SiAlN3 phosphor. The (Ca1-x-ySrxEu2+y)SiAlN3 phosphor has a europium content y of between about 0.003 and 0.009 and a strontium content x of between about 0.150 and 0.300.