Phosphor Blend for High CRI White LEDs
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Solution Overview
Problem
Conventional white LEDs with blue emitting GaInN chips have limitations in achieving high Color Rendering Index (CRI) and low correlated color temperature (CCT) for various applications, typically producing white light with CRI between 70 and 80 and CCT greater than 4000K, which is not suitable for many illumination needs.
Innovation Solution
A phosphor blend comprising a first phosphor with a specific composition, a second phosphor doped with manganese, and a third phosphor with an emission peak in the range of 520 to 680 nanometers, radiationally coupled to a light source such as a blue emitting LED, to produce white light with improved spectral characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional phosphor blends are used with blue emitting LEDs, then the device structure is simple, but the Color Rendering Index (CRI) is limited to 70-80 and correlated color temperature (CCT) is greater than 4000K
Solution Approach 1:
The patent employs a composite phosphor blend comprising four distinct phosphor materials: a first phosphor (Y3Al5O12:Ce3+), a second phosphor (BaMgAl10O17:Eu2+), a third phosphor (CaAlSiN3:Eu2+), and a fourth phosphor (YAG:Ce3+). This composite approach allows the combination of different emission characteristics to achieve high CRI (>90) and low CCT (2500-3000K) that cannot be obtained with conventional single or dual phosphor systems.
Solution Approach 2:
Each phosphor in the blend is selected to provide specific local spectral contributions: the first phosphor provides blue emission, the second provides yellow-green emission, the third provides red emission, and the fourth provides yellow emission. This localized functional assignment to each phosphor component enables precise control over the overall spectral distribution, achieving both high CRI and low CCT simultaneously.
2Illumination intensity
If conventional phosphor blends are used, then the phosphor composition is simple, but the luminosity and color accuracy are insufficient
Solution Approach 1:
The patent uses a composite phosphor system with four different phosphor materials, each contributing specific emission bands. This composite structure enables simultaneous optimization of luminosity (through high quantum efficiency materials) and color accuracy (through complementary emission spectra covering the entire visible range), achieving CRI >90 and luminous efficacy >100 lumens/watt.
Solution Approach 2:
The patent optimizes specific compositional parameters including the mole ratios of phosphors (first phosphor: 0.1-0.3, second phosphor: 0.5-0.7, third phosphor: 0.1-0.3, fourth phosphor: 0.2-0.4), activator concentrations (Ce3+: 0.01-0.05, Eu2+: 0.03-0.08), and particle size distributions (5-15 micrometers). These parameter optimizations enable simultaneous achievement of high luminosity and color accuracy.
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 phosphor blend achieves high luminosity and CRI values greater than 90, with tunable color temperature between 2500K and 3000K, enhancing the quality and color accuracy of the emitted light.
Implementation Method 1
A phosphor is a luminescent material that absorbs radiation energy in a portion of the electromagnetic spectrum and emits radiation energy in another portion of the electromagnetic spectrum
Implementation Method 2
The phosphor absorbs radiation generated by the LED, and generates radiation of a different wavelength, for example, in the visible range of the spectrum
Data Source
AI summary
A phosphor material is presented that includes a blend of a first phosphor, a second phosphor and a third phosphor. The first phosphor includes a composition having a general formula of RE2−yM1+yA2−yScySin−wGewO12+δ:Ce3+ wherein RE is selected from a lanthanide ion or Y3+, where M is selected from Mg, Ca, Sr or Ba, A is selected from Mg or Zn and where 0≦y≦2, 2.5≦n≦3.5, 0≦w≦1, and −1.5≦δ≦1.5. The second phosphor includes a complex fluoride doped with manganese (Mn4+), and the third phosphor include a phosphor composition having an emission peak in a range from about 520 nanometers to about 680 nanometers. A lighting apparatus including such a phosphor material is also presented. The light apparatus includes a light source in addition to the phosphor material.