Green Phosphor Composition for High-Temperature LED Color Stability
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Solution Overview
Problem
Eu-activated alkaline earth orthosilicate phosphors used in high load LED light-emitting devices experience significant temperature quenching, leading to a loss of emission intensity and color balance issues due to differing temperature effects on green and red luminescence, resulting in color discrepancies.
Innovation Solution
A green light-emitting fluorescent substance with the formula (Sr1-xEu x )3-yAl3+zSi13-zO2+uN21-w, where x, y, z, and u-w are within specific ranges, is developed, combined with a red light-emitting fluorescent substance, to maintain emission intensity and color balance even at high temperatures, using a specific crystal structure and production process to enhance quantum efficiency and temperature stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Eu-activated alkaline earth orthosilicate phosphors are used in high load LED light-emitting devices, then high luminous efficiency and color gamut are achieved, but temperature quenching causes significant loss of emission intensity and color balance
Solution Approach 1:
The patent modifies the chemical composition parameters of the orthosilicate phosphor by introducing Al5+ ions to substitute for Si4+ ions in the crystal lattice. This compositional parameter change creates charge compensation mechanisms that stabilize the Eu2+ emission centers against thermal deactivation, thereby reducing temperature quenching while preserving high luminous efficiency at operating temperatures.
Solution Approach 2:
The invention creates a composite phosphor material system combining Eu2+ activators with Al-doped orthosilicate host lattice. This composite structure integrates multiple functional elements: Eu2+ provides the luminescent centers, while Al3+ doping creates charge compensation sites and modifies the crystal field environment. The synergistic interaction between these components achieves both high efficiency and temperature stability that neither component could provide alone.
2Illumination intensity
If conventional phosphors are used to achieve high color gamut, then green and red luminescence are produced, but color balance is lost due to differential temperature quenching effects
Solution Approach 1:
The patent applies parameter changes to the phosphor composition by controlling the Al/Si ratio and Eu concentration within specific ranges. These compositional parameters are optimized to achieve differential effects: the Al doping level is tuned to provide sufficient charge compensation for Eu2+ stability, while the Eu concentration is controlled to maintain strong emission. This parameter optimization ensures that both green and red phosphors exhibit similar thermal stability characteristics, preserving color balance across the operating temperature range while maintaining wide color gamut.
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 maintains high quantum efficiency and prevents color discrepancies across a wide temperature range, ensuring consistent red and green light emission, thereby improving the color rendition and luminous efficiency of LED light-emitting devices.
Implementation Method 1
Eu-activated alkaline earth orthosilicate phosphors are typical examples of fluorescent substances emitting green or red luminescence under excitation by blue light
Implementation Method 2
When thus heated, the fluorescent substances generally lose emission intensity. Accordingly, it is desired to provide a fluorescent substance less undergoing the decrease of emission intensity (temperature quenching) even if the temperature rises considerably
Data Source
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AI summary
The embodiment provides a green light-emitting fluorescent substance having high quantum efficiency and also a light-emitting device comprising that substance so as to less undergo color discrepancies. The fluorescent substance is generally represented by (Sr1-xEUx)3-yAl3+zSi13-zO2+uN21-w, and is a kind of the Sr3Al3Si13O2N21 phosphors. This substance also gives an X-ray diffraction pattern having a diffraction peak at 2θ of 15.2 to 15.5° and the half-width thereof is 0.14° or less. Further, the substance emits luminescence having a peak within 490 to 580 nm when excited by light of 250 to 500 nm. The light-emitting device provided by the embodiment comprises that substance in combination with a light-emitting element and a red light-emitting fluorescent substance.