Remote Phosphor LED Package for Light Extraction
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) face challenges in generating white light efficiently due to their inability to produce white light from their active layers, requiring multiple LEDs and complex fabrication, which increases cost and complexity, and suffer from low color rendering index and efficiency issues, especially with green LEDs, and photon losses due to scattering and back emission from phosphor layers.
Innovation Solution
The solution involves an LED package design with a reflective conversion material positioned remotely from the LED, using a thin and dense phosphor layer on a high reflective surface to down-convert light, minimizing backscatter and absorption, and incorporating neutral high reflectivity materials to direct down-converted light towards the user, thereby improving light extraction efficiency and color control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional LEDs use phosphor layers for wavelength conversion, then white light can be generated, but photon losses occur due to scattering and back emission
Solution Approach 1:
The patent inverts the conventional LED structure by placing the phosphor layer on the far side of the LED chip rather than directly on top. This inversion allows the LED to emit light forward without immediate phosphor conversion, reducing backscatter into the active region and improving overall light extraction efficiency while minimizing photon losses.
2Illumination intensity
If multiple LEDs are combined to produce white light, then white light generation is achieved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent merges the wavelength conversion function directly into the LED package structure by integrating a phosphor layer with high reflectivity materials. This single-integration approach combines multiple functions (light emission, wavelength conversion, and light extraction enhancement) into one unified structure, eliminating the need for multiple separate LEDs or complex assembly processes.
3Productivity
If phosphor layer is placed close to LED for efficient wavelength conversion, then conversion efficiency improves, but scattering and absorption increase
Solution Approach 1:
The patent transitions from a vertical stacking approach (phosphor directly on LED) to a lateral positioning approach (phosphor on far side of chip). This dimensional change allows the phosphor layer to be positioned at an optimal distance where it can efficiently convert wavelengths while minimizing exposure to scattered and absorbed photons in the immediate vicinity of the LED active region.
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
This approach enhances light extraction efficiency, reduces photon losses, and allows for reproducible LED packages with improved color rendering and efficiency by minimizing scattering and absorption, while maintaining the conversion material cooler, thus achieving high efficacy and cost-effectiveness.
Implementation Method 1
The conversion material down-converts the wavelength of light from the LED. For example, if a nitride based blue emitting LED is surrounded by a yellow phosphor, some of the blue light will pass through the phosphor without being changed, while the remaining light will be down-converted to yellow.
Implementation Method 2
The reflective converter is arranged remote to the LED and has a reflective element. The reflective converter reflects the down-converted light and any LED light towards the user.
Data Source
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AI summary
An LED package comprises an LED for emitting LED light, and a conversion material remote to said LED for down-converting the wavelength of LED light. The package further comprises a reflector directing at least some of the LED light toward the conversion material; the conversion material down-converting the wavelength of at least some of the reflected LED light. A method for emitting light from an LED package comprising providing an LED, reflector and conversion material, and emitting light from said LED, at least some of the LED light emitted toward the reflector. The method further comprises reflecting at least some of the LED light toward the conversion material, and converting at least some of said reflected LED light at the conversion material. At least some of the converted reflected LED light is emitted by the LED package.