Light-emitting element with delayed fluorescence and fluorescent material

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Solution Overview

Problem

Existing light-emitting elements using organic compounds as light-emitting substances face challenges in achieving high luminous efficiency, particularly in converting triplet excited states into light emission efficiently.

Innovation Solution

A light-emitting element structure is developed that incorporates a thermally activated delayed fluorescent substance to generate singlet excited states from triplet excited states, combined with a fluorescent material to enhance light emission efficiency, by overlapping the emission spectrum of the thermally activated delayed fluorescent substance with the absorption band of the fluorescent material.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If phosphorescent compounds containing rare metals are used to convert triplet excited states into light emission, then luminous efficiency is improved, but cost and supply stability deteriorate

Engineering Contradiction:

Improveluminous efficiencyVSAvoidsupply stability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent replaces expensive rare metal phosphorescent compounds with organic compounds that have shorter lifetimes but are cheaper and more readily available. The organic light-emitting compound uses delayed fluorescence mechanism instead of phosphorescence, eliminating dependence on rare metals like iridium while maintaining light emission functionality.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the emission mechanism from phosphorescence (triplet state emission) to delayed fluorescence (singlet state emission). This involves modifying the energy level parameters and spin states of the light-emitting material, using compounds with small singlet-triplet energy gaps that enable reverse intersystem crossing and delayed fluorescence emission.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If organic compounds are used as light-emitting substances, then cost and availability are improved, but conversion efficiency of triplet excited states into light emission deteriorates

Engineering Contradiction:

Improvematerial availabilityVSAvoidtriplet excited state conversion efficiency

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent introduces a host-guest system where the organic light-emitting compound acts as a guest embedded in a host matrix. The host material facilitates the conversion process by providing appropriate energy levels and facilitating reverse intersystem crossing, enabling efficient triplet-to-singlet conversion without requiring the guest compound itself to have optimal phosphorescent properties.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent creates a composite light-emitting layer combining host and guest organic compounds with specifically designed energy level relationships. The composite system leverages the host's ability to stabilize excited states and the guest's emission properties, achieving efficient triplet excited state conversion through their synergistic interaction.

Inventive Principle:

Principle #40Composite materials

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 approach significantly improves the luminous efficiency of the light-emitting element by efficiently converting triplet excited states into singlet excited states and subsequent light emission, thereby achieving high external quantum efficiency.

Implementation Method 1

a singlet excited state is generated from a triplet excited state by reverse intersystem crossing

Methodology Applied

Scientific EffectReverse intersystem crossing:

Implementation Method 2

materials emitting delayed fluorescence have been studied. In the materials emitting delayed fluorescence, a singlet excited state is generated from a triplet excited state by reverse intersystem crossing

Methodology Applied

Scientific EffectThermally activated delayed fluorescence:

Implementation Method 3

light emission from the singlet excited state (S1) is referred to as fluorescence

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 4

by overlapping the emission spectrum of the thermally activated delayed fluorescent substance with the absorption band of the fluorescent material

Methodology Applied

Scientific EffectEnergy transfer:

Data Source

PatentUS20250160108A1Light-emitting element

Publication Date: 2025.05.15 SEMICON ENERGY LAB CO LTD

AI summary

To provide a light-emitting element which uses a fluorescent material as a light-emitting substance and has higher luminous efficiency. To provide a light-emitting element which includes a mixture of a thermally activated delayed fluorescent substance and a fluorescent material. By making the emission spectrum of the thermally activated delayed fluorescent substance overlap with an absorption band on the longest wavelength side in absorption by the fluorescent material in an S1 level of the fluorescent material, energy at an S1 level of the thermally activated delayed fluorescent substance can be transferred to the S1 of the fluorescent material. Alternatively, it is also possible that the S1 of the thermally activated delayed fluorescent substance is generated from part of the energy of a T1 level of the thermally activated delayed fluorescent substance, and is transferred to the S1 of the fluorescent material.