Conversion LED with Garnet and Nitridoaluminosilicate Phosphors
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Solution Overview
Problem
Conventional conversion LEDs experience significant conversion efficiency losses and chromaticity instability, especially at high currents, due to the instability of nitride or oxinitride luminescent substances, which affects their color rendering index and service life.
Innovation Solution
A conversion LED is developed using a combination of a novel green garnet luminescent substance and a narrowband red nitridoaluminosilicate luminescent substance, which provides high color rendering index, stability, and efficiency by shifting the emission towards shorter wavelengths and maintaining chromaticity coordinate stability even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If nitride or oxinitride luminescent substances are used in high-power LEDs, then the LED can operate at high currents, but significant conversion losses occur and chromaticity becomes unstable
Solution Approach 1:
The patent changes the chemical composition parameters of the luminescent substances by incorporating oxygen into the nitride structure (creating oxinitride) and adjusting the ratio of metal elements. This parameter change stabilizes the luminescent properties at high currents while maintaining high power operation, resolving the contradiction between power output and conversion efficiency stability.
Solution Approach 2:
The patent uses composite luminescent substances with multiple elements (Y, Gd, Lu, Al, Ga, N, O, and activators like Ce and Pr) to create a material that combines the high power capabilities of nitrides with the stability of oxides. This composite approach maintains conversion efficiency while enabling high-current operation.
2Illumination intensity
If multiple luminescent substances are added to improve color rendering index, then color rendering improves, but processing complexity and chromaticity coordinate stability deteriorate
Solution Approach 1:
The patent combines multiple functional requirements into a single luminescent substance by incorporating multiple rare earth elements (Ce for yellow-green emission, Pr for red emission) within one Y3Al5O12 garnet structure. This merging approach achieves high color rendering index while simplifying processing compared to using separate luminescent layers.
Solution Approach 2:
The Y3Al5O12:Ce,Pr garnet structure serves multiple functions simultaneously: it provides yellow-green emission from Ce, red emission from Pr, maintains chromaticity stability at high temperatures, and enables high power operation. This multi-functionality resolves the contradiction between color rendering improvement and processing complexity.
3Use of energy by moving object
If short-wave blue LED chips are used, then efficiency improves, but the blue-green gap in the spectrum increases
Solution Approach 1:
The patent enhances the spectral output at specific wavelengths by incorporating Pr elements that emit in the red region (600-650 nm). This local quality enhancement in the red spectrum compensates for the blue-green gap created by short-wave blue chips, while maintaining the high efficiency benefits of short-wave operation.
Solution Approach 2:
The Y3Al5O12:Ce,Pr garnet acts as an intermediary that absorbs short-wave blue light and converts it to both yellow-green (via Ce) and red (via Pr) emissions. This intermediary conversion process efficiently bridges the spectral gap while preserving the energy efficiency of short-wave excitation.
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 achieves an extremely high color rendering index of 96 to 98 with good red rendering, while maintaining high efficiency and stability, reducing conversion losses and improving the LED's service life, even when used with short-wave blue LED chips.
Implementation Method 1
a luminescent substance-containing layer which is positioned so that it intercepts the primary radiation emitted from the chip and converts at least some of the primary radiation of the chip into secondary radiation
Data Source
AI summary
Conversion LED emits primary radiation (peak wavelength 435 nm to 455 nm) and has a luminescent substance-containing layer positioned to intercept the primary radiation and convert it into secondary radiation. First and second luminescent substances are used. The first luminescent substance is a A3B5O12:Ce garnet type emitting yellow green having cation A=75 to 100 mol. % Lu, remainder Y and a Ce content of 1.5 to 2.9 mol. %, where B=10 to 40 mol. % Ga, remainder Al. The second luminescent substance is of the MAlSiN3:Eu calsine type which emits orange red, where M is Ca alone or at least 80% Ca and the remainder of M may be Sr, Ba, Mg, Li or Cu, in each case alone or in combination, wherein some of the Al up to 20%, can be replaced by B, and wherein N can be partially replaced by O, F, Cl, alone or in combination.