Color Micro-LEDs via Blue Pump and Red Phosphor Conversion
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Solution Overview
Problem
Current LED technologies are inadequate for producing high-resolution, high-luminance displays in small form factors, such as micro-displays and pico-projectors, due to manufacturing challenges with red micro-LEDs and limitations in existing technologies like OLEDs and micro-LED matrices.
Innovation Solution
A manufacturing method that uses Metal Organic Vapour Phase Epitaxy based Selective Area Growth to create micro-light emitting diodes capable of producing blue, green, and red light, where red light is generated through the conversion of blue or green light by photoluminescence, using a substrate with buffer layers and dielectric masks, and bonding red emitting structures on top of blue or green emitting structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If red, green and blue LEDs are used in each cell to achieve high resolution and high luminance, then display quality is improved, but device size increases making it unsuitable for micro-displays and pico-projectors
Solution Approach 1:
The invention segments the light generation function by separating the blue LED emission from the red light generation. Instead of using three separate LEDs (red, green, blue) in each cell, the patent uses a blue LED combined with a red phosphor converter, dividing the color generation into distinct functional components that can be integrated in a smaller footprint.
Solution Approach 2:
The invention changes the physical parameter of light wavelength conversion by using photoluminescence conversion. The blue LED emits at a specific wavelength, and the red phosphor material converts this blue light to red light through photoluminescence, enabling red light generation without requiring a red LED, thus reducing device size.
2Ease of manufacture
If blue and green micro-LEDs are manufactured, then green and blue light emission is achieved, but red micro-LED manufacturing becomes very complex due to low growth temperature and lattice mismatching
Solution Approach 1:
The invention introduces a red phosphor converter as an intermediary between the blue LED and the final red light output. Instead of directly manufacturing red micro-LEDs (which requires complex low-temperature growth and lattice matching), the patent uses the blue LED as a pump source and the red phosphor material as a mediator to convert blue light to red light, significantly simplifying the manufacturing process.
Solution Approach 2:
The invention replaces the mechanical/physical process of growing red micro-LED crystals (which requires precise temperature control and lattice matching) with an optical conversion process. The red phosphor converter absorbs blue photons and emits red photons through photoluminescence, substituting a complex materials growth process with a simpler optical conversion approach.
3Illumination intensity
If OLEDs with color filters or converters are used, then color display is achieved, but high resolution and high luminance cannot be obtained due to cell size and technology limitations
Solution Approach 1:
The invention uses composite material structures combining blue LED materials with red phosphor converter materials. This composite approach leverages the high efficiency and small size of blue micro-LEDs while adding the wavelength conversion capability of red phosphors, achieving both high luminance (from the efficient blue LED) and red color output (from the phosphor converter) in a compact structure suitable for high-resolution displays.
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 light emitting devices with high resolution and high luminance, suitable for micro-displays and pico-projectors, by simultaneously generating blue, green, and red light, overcoming the complexity of manufacturing red micro-LEDs and enhancing luminance.
Implementation Method 1
each color micro-light emitting diode is capable of generating a light having blue wavelengths by electroluminescence
Implementation Method 2
a light having green wavelengths by electroluminescence
Implementation Method 3
a light having red wavelengths by conversion of blue or green wavelengths by photoluminescence
Data Source
Figure 1~5
Figure 6~7
AI summary
A light emitting device (9) comprises a substrate (1), at least one green emitting structure (6) defined on at least one first area of at least one part (5) of this substrate (1), at least one blue emitting structure (7) defined on at least one second area of this part (5) of the substrate (1), and at least one red emitting structure (8) bonded on top of at least one sub-part of at least one blue emitting structure (7) defined on this part (5) of the substrate (1). The red emitting structure (8) is arranged for converting a blue light emitted by this sub-part of blue emitting structure (7) into a red light by photoluminescence, and the green (6), blue (7) and red (8) emitting structures define a color micro-light emitting diode at least partly and are individually connected to an external driving circuit.