Ce3+ Doped Calcium Silicate Phosphor for White LED Color Rendering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional white light emitting diodes (LEDs) face issues with heat emission, poor light emission efficiency, and limited color rendering due to the use of existing phosphors, which have narrow emission bandwidths and are sensitive to temperature, making them unsuitable for general lighting and liquid crystal display applications.
Innovation Solution
Development of Ce3+ doped calcium silicate phosphors with a broader emission bandwidth, spanning from 500 nm to 700 nm, excited by blue or near-UV LEDs, using a chemical formula (Ca1-yMy)2-x-zSiO4:Cex3+, where x, y, and z are within specific ranges, and incorporating metals like Mg, Sr, Ba, Li, Na, and K to enhance light emission efficiency and color rendering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If YAG-based phosphors are used in white LEDs, then the structure is simple and brightness is high, but the emission bandwidth is narrow and color rendering is poor
Solution Approach 1:
The patent employs a composite phosphor system combining YAG:Ce3+ with calcium silicate-based phosphors (such as CaAlSiN3:Eu2+ or Sr2Si5N8:Eu2+). This composite approach allows the YAG component to provide high brightness through its broad absorption spectrum, while the calcium silicate component extends the emission bandwidth into the red region (600-700 nm), thereby achieving both high brightness and improved color rendering characteristics
Solution Approach 2:
The patent introduces aluminum and nitrogen dopants at specific lattice positions within the calcium silicate structure to locally modify the emission properties. The Eu2+ dopant is strategically positioned to emit in the red spectral region, creating localized emission zones that complement the yellow emission of YAG:Ce3+ and fill the spectral gaps for improved color rendering
2Ease of manufacture
If Eu2+-doped strontium silicate phosphor is used, then the emission bandwidth is narrow, but the phosphor can be manufactured with simple process, but it emits orange light rather than yellow light
Solution Approach 1:
The patent modifies the emission color from orange to yellow by changing the dopant ion from Eu2+ to Ce3+ in the calcium silicate host. Ce3+ doping shifts the emission peak to approximately 560-580 nm (yellow region) while maintaining the cubic crystal structure and simple manufacturing process. The activation energy and emission wavelength are tuned by adjusting the Ce3+ concentration and host composition ratios
3Illumination intensity
If near-UV LED with three phosphors is used, then R-G-B type white light is generated, but heat emission is excessive and emission efficiency is poor
Solution Approach 1:
The patent extracts and eliminates two of the three phosphors required for R-G-B white light generation, retaining only the yellow-emitting phosphor (YAG:Ce3+) combined with a red-emitting calcium silicate phosphor. This simplifies the system from three-phosphor to two-phosphor configuration, reducing material complexity and heat generation while maintaining adequate white light output through optimized spectral composition
Solution Approach 2:
The patent changes the excitation wavelength from near-UV (380-405 nm) to blue (430-470 nm) by switching from three-phosphor to two-phosphor system. This parameter change improves emission efficiency because blue LEDs have higher external quantum efficiency and lower heat generation compared to near-UV LEDs, while the two-phosphor down-conversion system maintains effective light conversion
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 Ce3+ doped calcium silicate phosphors achieve improved light emission efficiency and wider wavelength coverage, enabling the production of high-brightness white LEDs with enhanced color rendering, suitable for various lighting applications, including liquid crystal display backlights.
Implementation Method 1
Ce3+ doped calcium silicate phosphors with a broader emission bandwidth, spanning from 500 nm to 700 nm, excited by blue or near-UV LEDs
Data Source
AI summary
The present invention is directed to phosphors and white light emitting diodes and a method for preparing a Ce3+ doped calcium silicate phosphor represented by a chemical formula of (Ca1-yMy)2-x-zSiO4:Ce3+x,N+z, wherein x is 0<x≦0.5, y is 0≦y≦0.5, z is 0<z≦0.5, M is at least one metal selected from Mg, Sr and Ba, and N is at least one metal selected from Li, Na, K and Rb, as well as white LEDs produced comprising the same. The phosphor of the present invention can be excited using conventional InGaN-based blue light emitting diodes, as well as GaN-based near-UV light emitting diodes to emit light across the visible spectrum.