Composite Phosphor Layer for High-Temperature pc-LED Reliability
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Solution Overview
Problem
Conventional phosphor layers in phosphor converted LEDs (pc-LEDs) degrade rapidly under high temperature and optical flux, leading to premature reliability failures, especially at high power levels.
Innovation Solution
Incorporating a phosphor layer with a combined solid volume percentage of phosphor particles and polydisperse inorganic filler particles of greater than or equal to 70%, where the inorganic filler particles have a distribution of sizes from 0.1 micrometer to 10 micrometers, providing improved thermal stability and crack resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional phosphor layers with powder phosphors and polymer binders are used, then the device structure is simple and easy to manufacture, but the reliability deteriorates under high temperature and optical flux
Solution Approach 1:
The patent uses a composite phosphor layer comprising phosphor particles, inorganic filler particles, and binder material. The inorganic filler particles (such as alumina, silica, or zirconia) combined with phosphor particles create a composite structure that provides both mechanical stability and thermal resistance, resolving the contradiction between reliability and simplicity by introducing a multi-component composite rather than a simple single-material layer
Solution Approach 2:
The patent changes the physical and chemical parameters of the phosphor layer by controlling the volume percentage of phosphor particles (50-90 vol%), inorganic filler particles (10-50 vol%), and binder material (1-20 vol%). By optimizing these compositional parameters, the layer achieves improved high-temperature reliability while maintaining manufacturability through controlled formulation
2Power
If the phosphor layer operates at high power levels, then the light output increases, but the degradation rate accelerates due to high temperature
Solution Approach 1:
The inorganic filler particles in the phosphor layer have thermal expansion coefficients that match or complement the substrate and semiconductor layers. This reduces thermally-induced stress and cracking during high-power operation, allowing the device to maintain both high optical power output and operational stability by managing thermal expansion effects
Solution Approach 2:
The patent converts the harmful effect of high temperature into a beneficial outcome by using the thermal energy to activate the photoluminescent properties of the phosphor particles more efficiently. The inorganic filler particles help dissipate excess heat while the phosphor particles convert the remaining thermal energy into useful light output, transforming the thermal stress problem into enhanced luminescence
3Stability of the object's composition
If the phosphor layer uses high solid volume percentage, then the thermal stability improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent segments the phosphor layer into distinct functional components: phosphor particles for light conversion, inorganic filler particles for structural stability, and binder material for cohesion. This segmentation allows each component to be optimized independently for its specific function while maintaining overall thermal stability, reducing the manufacturing precision burden on the entire layer
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 significantly enhances the long-term reliability of pc-LEDs under high-temperature conditions, with a time-to-failure at least four times greater than comparative devices, while offering wider color tunability and improved color rendering quality.
Implementation Method 1
The phosphor layer absorbs energy and converts an entering wavelength to a lower-energy wavelength. For example, the phosphor layer down-converts high energy LED light into a more desirable color spectrum.
Implementation Method 2
a phosphor layer with a combined solid volume percentage of phosphor particles and polydisperse inorganic filler particles of greater than or equal to 70%, where the inorganic filler particles have a distribution of sizes from 0.1 micrometer to 10 micrometers, providing improved thermal stability and crack resistance
Data Source
AI summary
Light emitting diode (LED) devices comprise: a stack of semiconductor layers including an active region and a phosphor layer on the semiconductor layers, the phosphor layer comprising: phosphor particles, a binder material, and polydisperse inorganic filler particles. a combined solid volume percentage of the phosphor particles and the polydisperse inorganic filler particles of greater than or equal to 70% and in some embodiments, less than or equal to 90%.