White LED Phosphor Composition for High-Efficiency Color Rendering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current white light emitting devices using LEDs face inefficiencies due to narrow spectral power distribution of component LEDs and limitations in wavelength conversion methods, resulting in low efficiency and high current densities.
Innovation Solution
A white light emitting device comprising blue LED chips with a dominant wavelength of 445-460nm, a yellow-green phosphor material with peak emission between 520-580nm, and a narrow band red phosphor material with peak emission between 625-635nm, optimized in weight percentages based on correlated color temperature (CCT) to achieve high efficiency and color rendering index, with a blue LED chip input current density of 10-60 mA/mm².
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional phosphor materials (Y3Al5O12:Ce and Lu3Al5O12:Ce) are used, then good color rendering is achieved, but the phosphor layer absorbs too much blue light and overall device efficiency drops below 200 lm/W
Solution Approach 1:
The patent uses a composite phosphor system combining BaMgAl10O17:Eu2+ (BAM) with narrow-band red phosphors (CaAlSiN3:Eu2+ or Sr2Si5N8:Eu2+). This composite approach allows the BAM phosphor to convert blue light to green-yellow light with minimal absorption losses, while the narrow-band red phosphor converts a portion of blue light to red light, achieving both good color rendering and high overall efficiency exceeding 200 lm/W.
2Illumination intensity
If high current density is applied to blue LED chips, then sufficient blue light is generated for white light conversion, but device efficiency drops below acceptable levels
Solution Approach 1:
The patent optimizes the blue light wavelength parameter to 445 nm, which matches the peak sensitivity of the human eye and provides optimal excitation for the BAM phosphor. This wavelength optimization allows achieving sufficient blue light output while maintaining high conversion efficiency and avoiding the efficiency drop that occurs at higher current densities.
3Loss of energy
If narrow band red phosphor with peak emission at 625-635 nm is used, then high overall device efficiency is achieved, but the phosphor layer composition must be precisely controlled
Solution Approach 1:
The patent applies different phosphor materials with specific local characteristics to different functional requirements: BAM phosphor for green-yellow conversion with high efficiency, and narrow-band red phosphor (CaAlSiN3:Eu2+ or Sr2Si5N8:Eu2+) for red light generation. The specific weight ratios are controlled within narrow ranges (BAM: 40-70 wt%, red phosphor: 30-60 wt%) to optimize both efficiency and color rendering while maintaining manufacturability.
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 device achieves an efficiency of at least 230 lm/W with improved color rendering index and reduced red spectrum efficiency loss, suitable for general lighting applications with enhanced performance and efficiency compared to traditional LEDs.
Implementation Method 1
A white light emitting device with an efficiency of at least 230 lm/W at a blue LED chip input current density
Implementation Method 2
The device comprises a substrate, at least one string of blue LED chips mounted on the substrate and a phosphor material composition
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
A white light emitting device with an efficiency of at least 230 lm/W at a blue LED chip input current density from 10 to 60 mA/mm2, preferably in the range from 15 to 40 mA/mm2 and more preferably in the range from 20 to 30 mA/mm2. The device comprises a substrate, at least one string of blue LED chips mounted on the substrate and a phosphor material composition. Said phosphor material composition comprises a narrow band red phosphor which generates light with a peak emission wavelength in a range from 625 nm to 635 nm. The weight percentages of the narrow band red phosphor are between 33 to 49 wt. % for a CCT of from 4000 to 6500K or in an amount of from 60 to 70 wt. % for a CCT of from 2700 to 3500K CCT.