Quantum Well Light Conversion in Solid State LEDs
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Solution Overview
Problem
Conventional solid state light emitting diodes (LEDs) cannot generate white light from their active layers, requiring multiple LEDs and complex fabrication to produce a single color, which increases costs and complexity, and suffer from reduced efficiency and stability due to the use of external phosphors for downconversion.
Innovation Solution
Incorporating a quantum well structure within the LED that absorbs light from the active region and re-emits it at a different wavelength, eliminating the need for external phosphors and allowing for controlled light emission without the absorption and heat-related issues associated with downconversion materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If external phosphors are used for downconversion to generate white light, then white light can be produced, but light efficiency is reduced due to absorption and Stokes shift
Solution Approach 1:
The patent merges the downconversion function into the LED's active region by integrating a quantum well structure that directly converts blue light to yellow light within the semiconductor material itself, eliminating the need for separate external phosphor materials and reducing energy loss through absorption interfaces
Solution Approach 2:
The patent extracts the downconversion function from external phosphor materials and relocates it into the LED's internal quantum well structure, removing the harmful absorption and Stokes shift effects associated with external phosphors while maintaining the white light generation capability
2Illumination intensity
If current is increased to make blue LED bright enough for room illumination, then light output increases, but heat generation becomes excessive and damages downconverting material
Solution Approach 1:
The patent converts the harmful effect of high current operation by integrating the downconversion function internally, where the quantum well structure efficiently converts excess blue light energy to yellow light within the device, reducing the need for extreme current increases and thereby reducing heat generation and material damage
3Illumination intensity
If multiple LEDs are combined to produce white light, then white light can be generated, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent combines multiple light generation functions (blue light emission and yellow light conversion) into a single integrated LED device with an internal quantum well structure, eliminating the need for multiple separate LEDs and their associated complex control electronics and fabrication processes
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 enables the generation of white light without the need for multiple LEDs or complex fabrication, improving light efficiency and stability by directly converting blue light to yellow within the LED, reducing heat generation, and simplifying the manufacturing process.
Implementation Method 1
A quantum well structure is included that is integral to the emitter structure and has a plurality of layers having a composition and thickness such that the quantum well structure absorbs at least some of the light emitted from the active region
Implementation Method 2
the quantum well structure absorbs at least some of the light emitted from the active region and re-emits light of at least one different wavelength of light
Data Source
AI summary
A solid state light emitting device according to the present invention comprises an emitter structure having an active region of semiconductor material and a pair of oppositely doped layers of semiconductor material on opposite sides of said active region. The active region emits light at a first wavelength in response to an electrical bias across said doped layers. A quantum well structure is included that is integral to the emitter structure and has a plurality of layers having a composition and thickness such that the quantum well structure absorbs at least some of the light emitted from the active region and re-emits light of at least one different wavelength of light from said first wavelength.