Non-stoichiometric Tetragonal Alkaline Earth Silicate Phosphors for LED Stability
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Solution Overview
Problem
Conventional silicate phosphors used in light emitting devices (LEDs) suffer from significant brightness reduction and color shift at elevated temperatures due to temperature quenching, and are sensitive to water and humidity, limiting their stability and performance.
Innovation Solution
Employing non-stoichiometric tetragonal Alkaline Earth Silicate phosphors with divalent copper and europium as an activator, which exhibit improved temperature stability, reduced sensitivity to water and humidity, and enhanced emission intensity, achieved through a high-temperature solid state reaction process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional silicate phosphors are used in LEDs, then the device can be manufactured with standard materials, but the brightness decreases significantly at elevated temperatures due to temperature quenching
Solution Approach 1:
The patent modifies the chemical composition parameters of the silicate phosphor by incorporating specific ratios of alkaline earth metals (calcium, strontium, barium) and silicon dioxide, along with activators like europium and copper. This compositional parameter change creates a more thermally stable crystal lattice that resists temperature quenching while maintaining high brightness at elevated temperatures
Solution Approach 2:
The invention uses composite phosphor materials combining multiple alkaline earth metal silicates with specific activators. The composite structure of calcium strontium barium silicate with europium and copper activators creates synergistic effects that improve temperature stability while preserving illumination intensity
2Object-affected harmful factors
If conventional silicate phosphors are used, then the manufacturing process is simple, but the phosphors show high sensitivity to water and humidity
Solution Approach 1:
The patent changes the chemical composition parameters by optimizing the ratio of basic oxides to silicon dioxide and selecting specific alkaline earth metal combinations. This parameter optimization reduces the phosphor's chemical reactivity with water and humidity while improving overall stability and reliability in潮湿 environments
3Illumination intensity
If stoichiometric silicate phosphors are used, then the crystal structure is well-defined, but the emission intensity decreases at high temperatures
Solution Approach 1:
The patent employs parameter changes by adjusting the stoichiometric ratios and introducing non-stoichiometric compositions with excess silicon dioxide. This creates a more rigid and thermally stable crystal lattice that maintains high emission intensity even at elevated temperatures by reducing thermal vibrations and energy loss
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 provides LEDs with stable brightness and color rendering index (CRI) of 80-95, maintaining high performance from 2000K to 10000K, and improved resistance to water and humidity, making them suitable for high-brightness applications.
Implementation Method 1
The luminescent material absorbs at least a portion of the light emitted from the light emitting diode and emits light having a different wavelength from the absorbed light
Data Source
AI summary
Disclosed is a light emitting device employing non-stoichiometric tetragonal Alkaline Earth Silicate phosphors. The light emitting device comprises a light emitting diode emitting light of ultraviolet or visible light, and non-stoichiometric luminescent material disposed around the light emitting diode. The luminescent material adsorbs at least a portion of the light emitted from the light emitting diode and emits light having a different wavelength from the absorbed light. The non-stoichiometric luminescent material has tetragonal crystal structure, and contains more silicon in the crystal lattice than that in the crystal lattice of silicate phosphors having stoichiometric crystal structure. The luminescent material is represented as the formula (BauSrvCawCux)3−y(Zn,Mg,Mn)zSi1+bO5+2b:Eua. Light emitting devices having improved temperature and humidity stability can be provided by employing the non-stoichiometric tetragonal Alkaline Earth Silicate phosphors.