Organic Light Emitting Device Delayed Fluorescent Lifetime

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Solution Overview

Problem

Organic electroluminescent devices using delayed fluorescent materials face challenges in securing a sufficient lifetime, despite achieving high emission efficiency as reported in previous studies.

Innovation Solution

An organic light emitting device is designed with a light emitting layer comprising specific combinations of a first, second, third, and fourth organic compound, where the second compound is a delayed fluorescent material, and the concentrations and energy levels of these compounds are optimized to satisfy specific requirements, ensuring efficient energy transfer and prolonged emission lifetime.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a delayed fluorescent material is used in an organic electroluminescent device to improve emission efficiency, then light emission efficiency is enhanced, but device lifetime becomes insufficient

Engineering Contradiction:

Improvelight emission efficiencyVSAvoiddevice lifetime

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent employs a composite light emitting layer containing four different organic compounds with specific energy level relationships. The first compound (host material) has the highest triplet energy, the second compound (delayed fluorescent material) has intermediate triplet energy, the third compound (fluorescent material) has lower triplet energy, and the fourth compound has the lowest triplet energy. This composite structure enables efficient energy transfer cascades while distributing stress and degradation mechanisms across multiple materials, thereby maintaining high emission efficiency while improving device lifetime

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent systematically optimizes multiple parameters including the energy levels (ES1 and ET1 values), concentrations (mole percentages), and molecular structures of the four organic compounds. By adjusting these parameters to satisfy specific energy level relationships (ES1(1)>ES1(4)>ES1(2)>ES1(3) and ET1(1)>ET1(2)>ET1(3)>ET1(4)), the device achieves both high emission efficiency and improved lifetime through controlled energy transfer processes

Inventive Principle:

Principle #35Parameter changes

2Productivity

If energy is transferred from the delayed fluorescent material to the fluorescent light emitting material, then emission efficiency improves, but the delayed fluorescent material degrades faster reducing device lifetime

Engineering Contradiction:

Improveemission efficiencyVSAvoiddelayed fluorescent material lifetime

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The first organic compound serves as a host material and intermediary that receives energy from electrical excitation and transfers it to the second compound (delayed fluorescent material). The fourth organic compound acts as an energy sink that accepts excess energy from the third compound, preventing back-transfer and reducing degradation of the delayed fluorescent material. This intermediary structure distributes the energy transfer burden and protects the delayed fluorescent material from excessive degradation

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The light emitting layer uses a composite of four compounds where each material has a specific role: the host material (first compound) manages charge injection and initial energy transfer, the delayed fluorescent material (second compound) provides triplet state utilization, the fluorescent material (third compound) emits the primary light, and the fourth compound acts as an energy sink. This functional distribution in the composite material system improves overall device lifetime by preventing any single material from bearing excessive stress

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

The optimized composition achieves long-life light emission and stable performance by effectively utilizing the delayed fluorescent material, enhancing the device's operational longevity.

Implementation Method 1

A delayed fluorescent material is a material which, in an excited state, after having undergone reverse intersystem crossing from an excited triplet state to an excited singlet state, emits fluorescence when returning back from the excited singlet state to a ground state thereof

Methodology Applied

Scientific EffectReverse intersystem crossing:

Implementation Method 2

emits fluorescence when returning back from the excited singlet state to a ground state thereof

Methodology Applied

Scientific EffectFluorescence: Fluorescence

Implementation Method 3

the concentrations and energy levels of these compounds are optimized to satisfy specific requirements, ensuring efficient energy transfer and prolonged emission lifetime

Methodology Applied

Scientific EffectEnergy transfer:

Data Source

PatentUS20230225203A1Organic luminescent element

Publication Date: 2023.07.13 KYULUX INC

AI summary

An organic light emitting device having a light emitting layer that contains first to fourth organic compounds satisfying the following formulae has a long emission lifetime and is stable. The second organic compound is a delayed fluorescent material, and the amount of light emission from the fourth organic compound is the maximum. ES1 is a lowest excited singlet energy, ET1 is a lowest excited triplet energy. ES1(1)>ES1(4)>ES1(2)>ES1(3), ET1(1)>ET1(2)>ET1(3)>ET1(4).