White LED Phosphor Blend for High CRI Without Efficacy Loss
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Solution Overview
Problem
White light emitting LEDs face a trade-off between high color rendering index (CRI Ra) and luminous efficacy due to the inclusion of red and orange phosphors, which improve color rendering but decrease efficiency and conversion efficiency.
Innovation Solution
Incorporating a combination of yellow to green, broadband orange to red, and narrowband red photoluminescence materials in white light emitting devices, specifically using manganese-activated fluoride phosphors and calcium aluminum silicon nitride based phosphors, to optimize the emission spectrum and achieve high CRI Ra while maintaining luminous efficacy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If red and orange phosphors are included to improve color rendering, then CRI Ra is improved, but luminous efficacy decreases
Solution Approach 1:
The patent segments the red phosphor component into two distinct parts: a narrowband red phosphor (peak 610-650 nm, FWHM 30-80 nm) and a broadband orange-to-red phosphor (peak 580-620 nm, FWHM 50-100 nm). This segmentation allows each phosphor to perform its specialized function - the narrowband phosphor provides efficient red emission with minimal spectral overlap, while the broadband phosphor fills spectral gaps to improve color rendering, thereby resolving the contradiction between CRI and luminous efficacy.
Solution Approach 2:
The patent applies local quality by assigning different spectral characteristics to different phosphor components within the same system. The narrowband red phosphor concentrates emission in a specific wavelength range for high efficiency, while the broadband orange-to-red phosphor distributes emission across a wider range for improved color rendering. This localized functional differentiation enables simultaneous optimization of both luminous efficacy and color rendering properties.
2Illumination intensity
If red phosphors with broad emission spectrum are used to improve color rendering, then CRI Ra is improved, but conversion efficiency decreases
Solution Approach 1:
The patent divides the red phosphor function into two segments with distinct spectral profiles. The narrowband red phosphor (FWHM 30-80 nm) maintains high conversion efficiency by concentrating emission in a narrow band, while the broadband orange-to-red phosphor (FWHM 50-100 nm) improves color rendering by filling spectral gaps. This segmentation resolves the contradiction between conversion efficiency and color rendering that plagues conventional single-phosphor systems.
Solution Approach 2:
The patent creates a composite phosphor system combining narrowband red phosphor materials (such as K2SiF6:Mn4+, K2GeF6:Mn4+) with broadband orange-to-red phosphor materials (such as CaAlSiN3:Eu2+, Sr2Si5N8:Eu2+). This composite approach leverages the complementary strengths of each material type, achieving both high conversion efficiency and superior color rendering that neither material could achieve alone.
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 white light emitting devices to achieve CRI Ra of at least 90, CRI R9 of 50, and luminous efficacy of 330 lm/Wopt or higher across various color temperatures, meeting current lighting standards with improved color rendering and efficiency.
Implementation Method 1
white light emitting LEDs include one or more photoluminescence materials (typically inorganic phosphor materials), which absorb a portion of the blue light emitted by the LED and re-emit light of a different color (wavelength)
Data Source
AI summary
A light emitting device comprises: a solid-state light emitter which generates blue excitation light with a dominant wavelength from 440 nm to 470 nm; a yellow to green photoluminescence material which generates light with a peak emission wavelength from 500 nm to 575 nm; a broadband orange to red photoluminescence material which generates light with a narrowband peak emission wavelength from 580 nm to 620 nm; and a narrowband red manganese-activated fluoride phosphor which generates light with a peak emission wavelength from 625 nm to 635 nm. The device generates white light with a spectrum having a broad emission peak from about 530 nm to about 600 nm and a narrow emission peak and wherein the ratio of the peak emission intensity of the broad emission peak to the peak emission intensity of the narrow emission peak is at least 20%.