OLED Electron Transport Compound With High Tg and Color Purity

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Solution Overview

Problem

Existing organic electroluminescent devices face challenges in achieving high luminous efficiency and long lifespan due to low glass transition temperatures, which lead to high temperature deterioration and reduced performance, and current electron transport materials like Alq3 suffer from color purity issues in blue light-emitting devices.

Innovation Solution

An organic electroluminescent compound with a specific molecular structure that controls the binding position of substituents to optimize HOMO and LUMO levels and steric hindrance, increasing the glass transition temperature and enhancing electron transport efficiency, thereby improving device performance and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional electron transport materials like Alq3 are used, then electron transport capability is improved, but color purity deteriorates in blue light-emitting devices

Engineering Contradiction:

Improveelectron transport capabilityVSAvoidcolor purity

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the molecular structure parameters of electron transport materials by introducing specific substituents (fluorine atoms, aryl groups) at defined positions on the benzofluorene core. This changes the electronic properties (HOMO/LUMO levels) and steric characteristics of the material, enabling it to transport electrons effectively while maintaining color purity in blue OLEDs by preventing material migration to other layers

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates composite molecular structures by combining a benzofluorene core with triazine rings and various aryl substituents. This composite structure integrates the electron-transporting capability of the triazine-benzofluorene framework with the steric bulk and electronic properties of aromatic substituents, achieving both high electron mobility and color purity retention

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If glass transition temperature is low, then ease of manufacture is improved, but lifespan deteriorates due to crystallization and aggregation at high temperatures

Engineering Contradiction:

Improveprocessing flexibilityVSAvoiddevice lifespan

Core Design Contradiction:

Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The patent elevates the glass transition temperature (Tg) of the organic electroluminescent compound to 150°C or higher through molecular structure design. This parameter change ensures the material remains amorphous and stable during device operation and fabrication processes, preventing crystallization and aggregation that would otherwise reduce device lifespan, while still allowing standard manufacturing processes to be used

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If driving voltage is reduced, then energy efficiency is improved, but luminous efficiency may deteriorate

Engineering Contradiction:

Improvedriving voltageVSAvoidluminous efficiency

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The patent optimizes the HOMO and LUMO energy level parameters of the electron transport material to achieve better energy level alignment with adjacent layers. This parameter optimization facilitates efficient charge injection and transport at lower driving voltages while maintaining high electron mobility, thus achieving both low operating voltage and high luminous efficiency simultaneously

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 compound achieves low driving voltage, high luminous efficiency, and extended lifespan for organic electroluminescent devices by maintaining stability at high temperatures, addressing the limitations of previous materials.

Implementation Method 1

an electron transport material actively transports electrons from a cathode to a light-emitting layer

Methodology Applied

Scientific EffectElectron transport: Conduction (electrical)

Implementation Method 2

controls the binding position of substituents to optimize HOMO and LUMO levels

Methodology Applied

Scientific EffectEnergy level stabilization:

Implementation Method 3

If the glass transition temperature (Tg) of an organic electroluminescent compound is low, crystallization and aggregation of the material may occur

Methodology Applied

Scientific EffectThermal stability:

Implementation Method 4

increasing the glass transition temperature and enhancing electron transport efficiency

Methodology Applied

Scientific EffectGlass transition:

Data Source

PatentUS11785846B2Organic electroluminescent compound and organic electroluminescent device comprising the same

Publication Date: 2023.10.10 DUPONT SPECIALTY MATERIALS KOREA LTD

AI summary

The present disclosure relates to an organic electroluminescent compound and an organic electroluminescent device comprising the same. The organic electroluminescent compound of the present disclosure has a high glass transition temperature that can be used in a deposition process. Further, by comprising the organic electroluminescent compound of the present disclosure, an organic electroluminescent device having a low driving voltage, high luminous efficiency, and/or improved lifespan characteristics can be provided.