Planar Quantum Well LED Conversion Layer for Micronic Pixels

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Solution Overview

Problem

Existing optoelectronic devices using gallium nitride LEDs face challenges in efficiently converting blue light into other colors like red and green due to the instability of 3D quantum dots and the incompatibility of nanophosphors with micronic pixel sizes, leading to low luminosity and resolution.

Innovation Solution

A planar quantum well structure with a diffraction grating and lateral reflector is used to convert blue light into red or green light, where the diffraction grating enhances extraction efficiency, and the lateral reflector extends the effective length of the grating, allowing efficient emission of colored light from micronic devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If nanophosphors are used for light conversion, then conversion efficiency is improved, but pixel size compatibility deteriorates due to required thickness of several tens of microns

Engineering Contradiction:

Improvelight conversion efficiencyVSAvoidpixel size

Core Design Contradiction:

Loss of energyVSVolume of moving object

Solution Approach 1:

The patent changes the physical state and dimensional parameters of the phosphor material from 3D bulk nanophosphors (requiring tens of microns thickness) to 2D planar quantum wells (requiring only sub-micron thickness). This parameter transformation enables efficient light conversion while maintaining compatibility with micronic pixel sizes in OLED displays.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention transitions from three-dimensional nanophosphor particles to two-dimensional planar quantum well structures. This dimensional reduction allows the conversion layer to achieve sufficient optical absorption and emission efficiency within a thickness compatible with micronic pixel dimensions, resolving the contradiction between conversion efficiency and pixel size.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If 3D quantum dots are used for light conversion, then pixel size compatibility is improved, but stability deteriorates due to sensitivity to light flux and heat

Engineering Contradiction:

Improvepixel sizeVSAvoidstability under light flux and heat

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent employs planar quantum wells formed from layered semiconductor materials (such as MoS2, WS2, WSe2, MoSe2) that combine the advantages of two-dimensional confinement with enhanced thermal and optical stability compared to 3D quantum dots. This composite material approach maintains micronic pixel compatibility while improving reliability under operational conditions.

Inventive Principle:

Principle #40Composite materials

3Loss of energy

If conversion layer thickness is increased to improve absorption, then light conversion efficiency is improved, but aspect ratio constraint is violated

Engineering Contradiction:

Improvelight absorption efficiencyVSAvoidaspect ratio

Core Design Contradiction:

Loss of energyVSShape

Solution Approach 1:

The patent transforms the thickness parameter of the conversion layer from tens of microns (in nanophosphor approaches) to sub-micron scale (in planar quantum well structures). This parameter change enables sufficient optical absorption through enhanced exciton generation and radiative recombination in the 2D quantum well, while maintaining an aspect ratio compatible with micronic pixel geometries.

Inventive Principle:

Principle #35Parameter changes

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 stable and efficient conversion of blue light into red or green light, improving luminosity and resolution by enhancing the extraction efficiency of the converted radiation, suitable for micronic pixel sizes.

Implementation Method 1

a conversion layer which extends above the light emitting diode and which is configured to convert a part at least of the first radiation into a second radiation, by photoluminescence

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 2

a diffraction grating, configured to extract a part at least of the second radiation from the conversion layer

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 3

a lateral reflector having a reflective surface which extends transversally with respect to the conversion layer, facing a part at least of the lateral surface of the conversion layer

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS12484352B2Light emitting device, pixel comprising several such devices, matrix of pixels and associated manufacturing methods

Publication Date: 2025.11.25 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

An optoelectronic light emitting device includes a light emitting diode configured to emit a first radiation, a conversion layer including at least one planar quantum well configured to convert the first radiation into a second radiation, by photoluminescence, a grating for extracting the second radiation being etched on an upper face of the layer, and a lateral reflector having a reflective surface which extends facing part at least of a lateral surface of the conversion layer.