TADF-Quantum Dot Light-Emitting Device Narrow Spectrum

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Solution Overview

Problem

The existing light-emitting elements with thermally activated delayed fluorescence (TADF) and fluorescent materials face challenges in achieving deep chromaticity due to broad emission spectra, and increasing quantum dot concentration leads to reduced luminous efficiency and non-light emission radiation.

Innovation Solution

A light-emitting device configuration with a light-emitting layer containing dispersed thermally activated delayed fluorescence bodies and quantum dots, where the light emission spectrum of the TADF bodies overlaps with the absorption spectrum of the quantum dots, enabling efficient energy transfer and narrow spectrum light emission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If quantum dots are used as light emission material to achieve narrow light emission spectrum and deep chromaticity, then chromaticity is improved, but luminous efficiency decreases due to concentration reduction

Engineering Contradiction:

ImprovechromaticityVSAvoidluminous efficiency

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

The patent introduces a dispersing material as an intermediary host matrix that contains both quantum dots and TADF materials. The dispersing material provides a medium for energy transfer from TADF to quantum dots while maintaining quantum dot dispersion at optimal concentrations for narrow spectrum emission and deep chromaticity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the concentration parameter of quantum dots in the light emission material to an optimal range (0.1-10 mass%) and introduces TADF materials as energy donors. This parameter optimization allows achieving deep chromaticity through narrow quantum dot emission spectrum while maintaining high luminous efficiency via energy transfer from TADF materials.

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If concentration of quantum dots in light emission material is low to maintain narrow emission spectrum, then chromaticity is improved, but excitons are generated in dispersing material causing non-light emission radiation and reduced luminous efficiency

Engineering Contradiction:

ImprovechromaticityVSAvoidnon-light emission radiation

Core Design Contradiction:

Illumination intensityVSLoss of energy

Solution Approach 1:

The TADF material acts as an intermediary energy donor that absorbs excitons generated in the dispersing material and transfers energy to quantum dots. This intermediary mechanism prevents direct exciton generation in the dispersing material from causing non-light emission radiation, while maintaining low quantum dot concentration for narrow spectrum emission.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct exciton generation in quantum dots with an indirect energy transfer mechanism from TADF materials. This substitution eliminates the problem of exciton generation in dispersing material causing non-light emission radiation, while still achieving efficient quantum dot light emission with narrow spectrum and deep chromaticity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 configuration enhances light emission efficiency while reducing non-light emission processes, allowing for deep chromaticity and improved luminous efficiency by effectively utilizing quantum dots with a narrow emission spectrum.

Implementation Method 1

the singlet excitation state of the TADF material transitions to the singlet excitation state of the fluorescent material by the Förster transition to generate fluorescence

Methodology Applied

Scientific EffectFörster transition:

Implementation Method 2

a singlet excitation state of the TADF material is created from a triplet excitation state of the TADF material by reverse intersystem crossing

Methodology Applied

Scientific EffectReverse intersystem crossing:

Data Source

PatentUS11217763B2Light-emitting device including light-emitting layer in which thermally activated delayed fluorescence bodies and quantum dots are dispersed and manufacturing apparatus of light-emitting device

Publication Date: 2022.01.04 SHARP KK

AI summary

To provide a light-emitting device that can obtain fluorescence having a narrow spectrum more efficiently, a light-emitting device includes: a light-emitting layer in which thermally activated delayed fluorescence bodies and quantum dots are dispersed; a first electrode in a lower layer than the light-emitting layer; and a second electrode in an upper layer than the light-emitting layer, wherein a light emission spectrum of the thermally activated delayed fluorescence bodies and an absorption spectrum of the quantum dots at least partially overlap each other.