Rare Earth Doped LED Substrate for White Light Generation
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) cannot generate white light from their active layers and require multiple LEDs and complex fabrication to produce different colors, leading to increased costs, complexity, and reduced light efficiency due to the need for downconverting materials that absorb light and degrade over time.
Innovation Solution
Doping at least one layer of the LED or laser with rare earth or transition elements that absorb and re-emit light at different wavelengths, allowing a single LED to produce multiple colors, including white light, by manipulating the supply current and using substrates doped with these elements to change the color of emitted light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LEDs are combined to produce white light, then the light output and versatility are improved, but the device complexity, manufacturing cost, and control electronics requirements increase
Solution Approach 1:
The patent combines multiple light-emitting functions into a single LED device by integrating multiple active layers with different bandgaps within one semiconductor structure. This allows one LED to emit multiple wavelengths simultaneously, replacing the need for multiple separate LEDs while reducing device complexity and manufacturing cost
Solution Approach 2:
The invention creates a multi-functional LED that can emit different colors of light (blue, cyan, green, yellow, red) from a single device by incorporating multiple active layers with varying bandgap energies. This universal light source can be tuned to produce various colors including white light, eliminating the need for separate single-color LEDs
2Illumination intensity
If downconverting phosphor material is added to convert blue light to white light, then white light is produced, but the light emitting efficiency is reduced due to absorption and Stokes shift
Solution Approach 1:
The patent extracts and eliminates the need for external downconverting phosphor materials by directly generating multiple wavelengths including white light components from the active layers themselves. This removes the energy-lossy conversion step and allows direct emission of desired wavelengths
Solution Approach 2:
The invention uses the semiconductor active layers themselves as intermediaries to generate multiple wavelengths directly through electroluminescence, rather than using phosphor materials as intermediaries for wavelength conversion. This direct generation approach avoids the Stokes shift energy loss associated with phosphor downconversion
3Illumination intensity
If the supply current is increased to make blue LEDs bright enough for room illumination, then the light output is improved, but the heat generation increases and damages surrounding materials
Solution Approach 1:
The patent segments the light emission function across multiple active layers with different bandgaps, allowing the device to emit multiple colors including warmer spectrum colors (yellow, red) that contribute to perceived brightness without requiring excessive current. This distributes the luminous output across different wavelength regions, reducing the need to drive blue emission at very high currents
Solution Approach 2:
The invention changes the emission parameters by incorporating active layers with different bandgap energies that emit at different wavelengths. By including longer wavelength emitters (yellow, red) alongside blue, the overall luminous efficacy improves, allowing adequate illumination at lower current levels and reduced heat generation
4Adaptability or versatility
If different colors are generated from different types of LEDs, then color versatility is improved, but the fabrication complexity and control electronics requirements increase
Solution Approach 1:
The patent merges multiple color-emitting functions into a single semiconductor device by stacking multiple active layers with different bandgaps. This integration allows one fabrication process to produce multi-color LEDs, eliminating the need for separate fabrication lines for different color LEDs and simplifying manufacturing
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
Enables the production of white light and multiple colors from a single LED without the need for external phosphors, improving light efficiency and reducing the complexity and cost of manufacturing, while also enhancing temperature tolerance and safety by avoiding the heat-related degradation of downconverting materials.
Implementation Method 1
Depending on the type of dopant, light within a limited range of wavelengths is absorbed. A light within this absorption range pumps the electrons on the dopant ions to a higher energy state.
Implementation Method 2
The pumped electrons are drawn back to their natural equilibrium state and emit energy as light at a wavelength that depends upon the type of dopant ion.
Implementation Method 3
The new LED/lasers rely on the light absorption and emission properties of the doped substrate or absorption layer to produce new colors of light.
Data Source
AI summary
A solid state light emitting device comprising an emitter structure having an active region of semiconductor material and a pair of oppositely doped layers of semiconductor material on opposite sides of the active region. 'The active region emits light at a predetermined wavelength in response to an electrical bias across the doped layers. An absorption layer of semiconductor material is included that is integral to said emitter structure and doped with at least one rare earth or transition element. The absorption layer absorbs at least some of the light emitted from the active region and re-emits at least one different wavelength of light. A substrate is included with the emitter structure and absorption layer disposed on the substrate.