Green Quantum Dots and KSF Phosphor for Rec. 2020 Displays

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Solution Overview

Problem

Existing display devices face challenges in achieving a wide color gamut compliant with the Rec. 2020 standard using quantum dots, particularly due to the limitations of cadmium-based quantum dots, which are restricted by health and safety legislation, and the thermal stability issues with lead-containing phosphors in current configurations.

Innovation Solution

Combining blue-emitting LEDs with green-emitting heavy-metal-free quantum dots and red-emitting K2SiF6:Mn4+ (KSF) phosphor, where the quantum dots and phosphor are incorporated into polymer beads or films to maintain optical stability and prevent thermal degradation, allowing for a wide color gamut without using toxic materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If cadmium-based quantum dots are used to achieve narrow FWHM and wide color gamut, then color gamut coverage is improved, but compliance with RoHS health and safety legislation deteriorates

Engineering Contradiction:

Improvecolor gamut coverageVSAvoidRoHS compliance

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the material composition parameter from cadmium-based to heavy-metal-free quantum dots (e.g., Group III-V based materials like InP). This parameter change maintains the quantum dot emission properties while eliminating toxic substances, thus resolving the contradiction between color gamut performance and RoHS compliance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures including quantum dots combined with KSF phosphor (K2SiF6:Mn4+) to achieve the desired emission characteristics. This composite approach allows heavy-metal-free quantum dots to be paired with a narrowband-emitting red phosphor to achieve wide color gamut while maintaining RoHS compliance

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If Group III-V-based heavy-metal-free quantum dots are used to eliminate toxic materials, then RoHS compliance is improved, but FWHM broadens due to stronger quantum confinement effects

Engineering Contradiction:

ImproveRoHS complianceVSAvoidFWHM

Core Design Contradiction:

Object-affected harmful factorsVSIllumination intensity

Solution Approach 1:

The patent optimizes the particle size parameter of heavy-metal-free quantum dots to control the emission wavelength and FWHM. By precisely controlling the size of Group III-V based quantum dots, the patent achieves narrow emission peaks while maintaining heavy-metal-free composition

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent combines heavy-metal-free quantum dots with KSF phosphor to create a composite light-emitting system. The quantum dots provide green emission with controlled FWHM, while the KSF phosphor provides red emission, together achieving wide color gamut coverage compliant with Rec. 2020 standards

Inventive Principle:

Principle #40Composite materials

3Device complexity

If quantum dots are placed in close proximity to LED chip to form on-chip configuration, then device integration is improved, but thermal stability deteriorates due to heat exposure

Engineering Contradiction:

Improvedevice integrationVSAvoidthermal stability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent introduces an intermediary layer or structure between the LED chip and quantum dots that manages heat transfer. This intermediary element protects the quantum dots from direct thermal exposure while maintaining the on-chip integrated configuration, thus resolving the contradiction between integration and thermal stability

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs thin film encapsulation or protective layers around the quantum dots or between the quantum dots and LED chip. These thin films act as thermal barriers while maintaining optical transparency and structural integrity, protecting the quantum dots from thermal degradation in the integrated configuration

Inventive Principle:

Principle #30Flexible shells and thin films

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 combination of green-emitting quantum dots and KSF phosphor achieves a wide color gamut comparable to Rec. 2020 standards while maintaining optical stability and preventing thermal degradation, offering improved performance and compliance with health and safety regulations.

Implementation Method 1

green-emitting quantum dots

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Implementation Method 2

red-emitting K2SiF6:Mn4+ (KSF) phosphor

Methodology Applied

Scientific EffectPhotoluminescence: Photoluminescence

Data Source

PatentUS11043618B2Display devices comprising green-emitting quantum dots and red KSF phosphor

Publication Date: 2021.06.22 SAMSUNG ELECTRONICS CO LTD

AI summary

LED devices emitting white light comprise a blue-emitting LED, green-emitting quantum dots (QDs) and red-emitting K2SiF6:Mn4+ (KSF) phosphor. A backlight unit (BLU) for a liquid crystal display (LCD) comprises one or more blue-emitting LEDs and a polymer film containing green-emitting QDs and KSF phosphor. The QDs and/or KSF phosphor may be encapsulated in beads that provide protection from oxygen and/or moisture.