Fluorene Derivatives for OLED Electron Transport

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Solution Overview

Problem

Current organic electroluminescent devices face limitations in lifetime, efficiency, and operating voltage due to suboptimal electron-transport materials, particularly AlQ3, which decomposes during sublimation, leading to reduced quantum and power efficiency, and challenges in producing thicker layers without increasing voltage, and matrix materials for phosphorescent emitters have issues with chemical stability and compatibility with ketoketonate ligands.

Innovation Solution

The use of fluorene derivatives and spirobifluorene derivatives substituted with triazine or other electron-deficient nitrogen heterocycles, and carbazole or carbazole derivatives as matrix materials, which exhibit high thermal stability, long lifetimes, and low operating voltages, even with phosphorescent emitters containing ketoketonate ligands, enhancing electron injection and mobility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If AlQ3 is used as electron-transport material, then the device structure is simple and ease of manufacture is improved, but the material decomposes during sublimation leading to reduced quantum efficiency and power efficiency

Engineering Contradiction:

Improveease of manufactureVSAvoidquantum efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent changes the chemical composition parameters of the electron-transport material from AlQ3 to novel triaryl-substituted triazine derivatives, which have different thermal stability and electron mobility characteristics, thereby eliminating decomposition during sublimation while maintaining ease of manufacture

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite molecular structures combining triaryl groups with triazine cores, creating materials that integrate the benefits of both structural components: the stability of triaryl systems and the electron-transport capability of triazine rings, achieving both high quantum efficiency and ease of fabrication

Inventive Principle:

Principle #40Composite materials

2Device complexity

If AlQ3 is used as electron-transport material, then the device structure is simple, but the charge-carrier mobility is low resulting in higher operating voltages and lower power efficiency

Engineering Contradiction:

Improvedevice complexityVSAvoidpower efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent modifies the electron-transport properties by changing the molecular structure from AlQ3 to triaryl-substituted triazines, which exhibit higher charge-carrier mobility due to enhanced electron affinity and optimized HOMO-LUMO energy levels, thereby reducing operating voltage and improving power efficiency while maintaining simple device architecture

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the layer thickness is increased to avoid short circuits, then the reliability is improved, but the operating voltage increases due to low charge-carrier mobility

Engineering Contradiction:

ImprovereliabilityVSAvoidoperating voltage

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the material parameters by using triaryl-substituted triazine derivatives with superior electron mobility, which enables the construction of thicker electron-transport layers (improving reliability by preventing short circuits) without incurring voltage penalties, as the enhanced charge-carrier transport compensates for the increased path length

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If AlQ3 is used as electron-transport material, then the manufacturing process is simple, but the material cannot be applied by vapour deposition without leaving residue due to decomposition

Engineering Contradiction:

Improveease of manufactureVSAvoiddecomposition residue

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

The patent changes the thermal stability parameters of the electron-transport material by employing triaryl-substituted triazine derivatives, which possess higher decomposition temperatures and better thermal stability, enabling clean vapour deposition without residue formation while maintaining simple manufacturing processes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the decomposable AlQ3 material with stable triaryl-substituted triazines that do not require repeated source cleaning or replacement, effectively eliminating the need for maintenance of vapour-deposition sources and reducing operational complexity

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

5Device complexity

If AlQ3 is used as electron-transport material, then the device structure is simple, but decomposition products enter the OLED causing shortened lifetime and reduced efficiency

Engineering Contradiction:

Improvedevice complexityVSAvoidlifetime

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent changes the chemical stability parameters of the electron-transport material from AlQ3 to triaryl-substituted triazine derivatives, which exhibit superior thermal and chemical stability, preventing decomposition during device operation and thereby extending OLED lifetime while maintaining simple device structure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the potential harm of material decomposition into a benefit by selecting triaryl-substituted triazines that are specifically designed to be thermally stable, turning what would have been a manufacturing challenge into a reliability advantage with no decomposition products entering the device

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

6Device complexity

If conventional matrix materials are used for phosphorescent emitters, then the device structure is simple, but chemical stability and compatibility with ketoketonate ligands are poor

Engineering Contradiction:

Improvedevice complexityVSAvoidchemical stability

Core Design Contradiction:

Device complexityVSStability of the object's composition

Solution Approach 1:

The patent employs composite molecular structures combining fluorene or spirobifluorene cores with triazine or carbazole substituents, creating matrix materials that integrate the structural stability of the core with the chemical stability and ligand compatibility of the nitrogen-containing heterocyclic groups, achieving both simple device structure and superior chemical stability with ketoketonate ligands

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

These materials result in organic electroluminescent devices with improved efficiency, extended lifetimes, and reduced operating voltages, overcoming the limitations of previous materials by providing better electron transport and stability, especially when used as both electron-transport and matrix materials.

Implementation Method 1

Methodology Applied

Scientific EffectElectron transport: Conduction (electrical)

Implementation Method 2

it cannot be applied by vapour deposition without leaving a residue, since it partially decomposes at the sublimation temperature

Methodology Applied

Scientific EffectSublimation: Sublimation

Data Source

PatentUS9199972B2Materials for organic electroluminescent devices

Publication Date: 2015.12.01 MERCK PATENT GMBH

AI summary

The present invention relates to organic electroluminescent devices which comprise fluorene derivatives and spiro bifluorene derivatives as matrix material for phosphorescent emitters.