Solid State Lighting Without Phosphor Converters
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Solution Overview
Problem
Conventional solid-state lighting (SSL) devices require converter materials to produce white light, which have drawbacks such as low optical efficiency and reliability due to the absorption and heat dissipation of emissions, as well as complex and costly manufacturing processes.
Innovation Solution
SSL devices are designed without converter materials by using a substrate with semiconductor materials arranged in series, including N-type and P-type GaN materials, and active regions with sub-regions that produce multiple emissions with different wavelengths to approximate white light, utilizing MOCVD techniques for epitaxial growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If converter materials are used to produce white light, then white light can be achieved, but optical efficiency decreases and heat dissipation increases
Solution Approach 1:
The patent removes the converter material layer from the LED structure, extracting the problematic component that causes energy loss. Instead of using a blue LED with yellow phosphor converter, the invention uses multiple LED chips emitting at different wavelengths (violet, blue, cyan, green, yellow-green, yellow) that directly combine to produce white light, eliminating the energy-wasting conversion process
Solution Approach 2:
The patent employs a composite approach by combining multiple semiconductor materials with different bandgaps (GaN, AlGaN, InGaN) in a single LED device. Each material emits at a specific wavelength range, and their combined emissions produce white light directly without requiring external converter materials, thus maintaining high optical efficiency
2Illumination intensity
If converter materials are used to produce white light, then white light can be achieved, but reliability decreases due to heat dissipation
Solution Approach 1:
The patent removes the converter material layer from the LED structure, extracting the problematic component that causes energy loss. Instead of using a blue LED with yellow phosphor converter, the invention uses multiple LED chips emitting at different wavelengths (violet, blue, cyan, green, yellow-green, yellow) that directly combine to produce white light, eliminating the energy-wasting conversion process
Solution Approach 2:
The patent converts the challenge of achieving white light without energy loss into a benefit by using multiple quantum well structures with different indium compositions. Each quantum well emits at a optimized wavelength, and the combination naturally produces white light with minimal heat generation, turning the complexity of wavelength mixing into an advantage for reliability
3Illumination intensity
If converter materials are used in SSL devices, then white light can be produced, but manufacturing complexity and costs increase
Solution Approach 1:
The patent merges multiple light-emitting functions into a single integrated LED device structure. Instead of separately manufacturing blue LEDs and yellow phosphor materials and then assembling them, the invention integrates multiple quantum well active regions with different emissions directly into one LED chip, simplifying the manufacturing process and reducing assembly steps
Solution Approach 2:
The patent creates a universal LED device that can produce white light directly without requiring additional converter materials or complex assembly processes. The multi-quantum well structure serves multiple functions simultaneously: generating different wavelengths, combining them into white light, and maintaining high efficiency, all within a single device architecture
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 higher optical efficiency, increased reliability, and reduced manufacturing complexity and costs by eliminating the need for converter materials, resulting in improved performance and longevity of SSL devices.
Implementation Method 1
the GaN/InGaN MQWs 16 of the LED die 4 produce a first emission (e.g., a blue light)
Implementation Method 2
the LED die 4 can include a substrate 12, an N-type gallium nitride (GaN) material 14, GaN/indium gallium nitride (InGaN) multiple quantum wells ("MQWs") 16, a P-type GaN material 18, a first contact 20, and a second contact 22. Referring to both FIGS. 1A and 1B, in operation, an electrical voltage is applied between the first and second contacts 20 and 22. In response to the applied voltage, the GaN/InGaN MQWs 16 of the LED die 4 produce a first emission (e.g., a blue light) that stimulates the converter material 6 to emit a second emission (e.g., a yellow light). The combination of the first and second emissions appears white to human eyes if matched appropriately.
Data Source
AI summary
Solid state lighting devices that can produce white light without a phosphor are disclosed herein. In one embodiment, a solid state lighting device includes a first semiconductor material, a second semiconductor material spaced apart from the first semiconductor material, and an active region between the first and second semiconductor materials. The active region includes a first sub-region having a first center wavelength and a second sub-region having a second center wavelength different from the first center wavelength.