White LED Phosphor Composition 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, with specific peak emission wavelengths and full width at half maximum (FWHM) emission intensities, to generate white light with high CRI Ra and improved 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 increases, but luminous efficacy decreases
Solution Approach 1:
The red phosphor is divided into two distinct components: a narrowband red phosphor (peak 610-650 nm, FWHM 30-80 nm) and a broadband orange-red phosphor (peak 580-620 nm, FWHM 50-100 nm). This segmentation allows each component to serve a specific function - the narrowband component provides efficient red emission while the broadband component fills spectral gaps for improved color rendering, resolving the contradiction between efficacy and rendering quality
Solution Approach 2:
The invention uses a composite phosphor system combining multiple materials with different emission characteristics. The yellow-green phosphor (Y3Al5O12:Ce, peak 540-560 nm), narrowband red phosphor, and broadband orange-red phosphor work together in a composite formulation, where each material contributes specific spectral properties to achieve both high luminous efficacy and superior color rendering (CRI Ra≥90)
2Illumination intensity
If broadband orange to red phosphors are used to improve color rendering, then CRI Ra increases, but conversion efficiency decreases
Solution Approach 1:
Different regions of the spectrum are addressed with locally optimized phosphor properties. The narrowband red phosphor concentrates energy in the 610-650 nm region for efficient conversion, while the broadband orange-red phosphor specifically fills the 580-620 nm spectral gap. This local quality optimization ensures each phosphor component operates at peak efficiency for its designated spectral region, improving overall conversion efficiency while maintaining color rendering quality
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 combination of these materials enables white light emitting devices to achieve CRI Ra of at least 90, CRI R9 of at least 50, and luminous efficacy of at least 330 lm/Wopt, while meeting current lighting standards and optimizing luminous efficacy.
Implementation Method 1
white light emitting LEDs include one or more photoluminescence materials, which absorb a portion of the blue light emitted by the LED and re-emit light of a different color
Data Source
AI summary
An exemplary light emitting device includes 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 where 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%.