Vertical LED Stack with Angled Facets and Bragg Reflector
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Solution Overview
Problem
Conventional LED technologies face limitations in generating white light efficiently, including energy losses, limited lifetime, and low reliability due to the use of phosphors for color conversion, and the inability to achieve homogenized color emission with discrete LED chips.
Innovation Solution
A semiconductor-based LED stack design with angled facets and a distributed Bragg reflector allows for optimal color mixing by stacking blue, green, and red LEDs, eliminating the need for phosphors and enabling lossless white light generation with prolonged lifetimes and high reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If phosphors are used for color down conversion in LEDs, then broadband white light emission is achieved, but quantum efficiency and luminous efficiency are reduced due to Stokes-wave energy loss
Solution Approach 1:
The invention segments the broadband light generation into multiple monochromatic LED chips emitting at different wavelengths (blue, green, red) stacked vertically. Each chip emits narrowband light at its specific wavelength, and the combination of these segmented spectral components creates broadband white light without the energy losses associated with phosphor down-conversion.
Solution Approach 2:
The invention transitions from a planar phosphor-based conversion approach to a vertical stacking configuration in the third dimension. Multiple LED chips are stacked vertically with each emitting through a common exit surface, utilizing spatial arrangement to achieve spectral combination while maintaining high quantum efficiency of individual emitters.
2Adaptability or versatility
If discrete LED chips are mounted on a single package, then multiple colors can be emitted, but color homogenization is poor and discrete colors are visible to the naked eye
Solution Approach 1:
The invention employs a nested vertical stacking configuration where multiple LED chips are positioned one above another, with each chip's light emission path nested through the transparent or semi-transparent structures of adjacent chips. This nested arrangement allows all color components to converge through a single exit surface, achieving homogeneous color mixing.
Solution Approach 2:
The invention resolves the color homogeneity problem by moving from a lateral arrangement of discrete chips to a vertical stacking configuration. The vertical dimension allows light from all chips to travel through a common path and exit surface, enabling the human eye to perceive a uniform mixed color rather than discrete separate color sources.
3Illumination intensity
If phosphors are used for color conversion, then white light is generated, but device lifetime and reliability are reduced
Solution Approach 1:
The invention extracts and eliminates the phosphor material from the LED structure, replacing it with a stack of monochromatic LED chips. This removal of phosphors eliminates the degradation mechanisms associated with phosphor materials (such as thermal degradation, moisture sensitivity, and quantum efficiency decay), thereby significantly improving device lifetime and reliability while maintaining white light emission capability.
Solution Approach 2:
The invention replaces the fragile, short-lived phosphor materials with robust, long-lived semiconductor LED chips. LED chips have demonstrated operational lifetimes exceeding 50,000 hours with high reliability, compared to phosphors which degrade more rapidly under operational conditions. This substitution uses more durable components to achieve the same white light emission function.
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 achieves high quantum efficiency, long lifetimes, and reliable white light emission by ensuring optical color mixing and minimizing light absorption and leakage, tapping the full potential of LEDs.
Implementation Method 1
a first distributed Bragg reflector disposed between the top end of the first light emitting diode and a bottom end of the second light emitting diode to allow light from the first light emitting diode to pass through and to reflect light from the second light emitting diode
Implementation Method 2
a first light emitting diode for emitting light having a first wavelength, the first light emitting diode comprising angled facets to reflect incident light in a direction toward a top end of the first light emitting diode
Implementation Method 3
LEDs are optoelectronic devices, which emit light by recombining injected electrons and holes radiatively
Implementation Method 4
Phosphorescent materials that emit light when exposed to certain wavelengths of radiation are traditionally used for color conversion in light-emitting diodes (LEDs). A device may emit a high-energy photon, and the phosphor may absorb it and then re-emit a lower-energy and thus differently colored photon
Data Source
AI summary
Methods and systems are provided that may be used to utilize and manufacture a light sources apparatus. A first light emitting diode emits light having a first wavelength, and a second light emitting diode for emitting light having a second wavelength. Each of the first and second light emitting diodes may comprise angled facets to reflect incident light in a direct toward a top end of the first light emitting diode. The second light emitting diode comprising angled facets may reflect incident light in a direction toward a top end of the second light emitting diode. A first distributed Bragg reflector is disposed between the top end of the first light emitting diode and a bottom end of the second light emitting diode to allow light from the first light emitting diode to pass through and to reflect light from the second light emitting diode.