Monoamine Charge Transport Material for Stable OLEDs

Solution Overview

Problem

Conventional organic electroluminescent elements produced by wet film formation methods face issues with solubility, crystallization, heat resistance, and luminescent efficiency due to the use of halogenated solvents and low-molecular weight charge transport materials, leading to poor driving stability and low triplet excitation levels.

Innovation Solution

A monoamine compound with a specific triphenylamine structure is developed, offering excellent solubility, noncrystalline properties, and high triplet excitation levels, enabling the formation of a thermally and electrochemically stable charge transport material that can be used in organic electroluminescent elements for improved luminescent efficiency and driving stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If halogenated solvents are used to improve solubility of charge transport materials, then solubility is improved, but environmental burden increases and material purity deteriorates

Engineering Contradiction:

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the chemical structure of charge transport materials by introducing specific molecular weight ranges (500-5000) and functional groups to enhance solubility in non-halogenated solvents, thereby eliminating environmental burden while maintaining adequate solubility for wet film formation

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs conventional, easily available non-halogenated solvents (such as toluene, xylene, chlorobenzene alternatives) that are environmentally friendly and do not require special handling, replacing expensive and hazardous halogenated solvents

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If low-molecular weight charge transport materials are used to improve charge transport properties, then charge transport efficiency is improved, but thermal stability and electrochemical stability deteriorate

Engineering Contradiction:

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent optimizes the molecular weight parameter to a specific range (500-5000), balancing the competing requirements: low enough to maintain good charge transport properties and solubility, but high enough to provide adequate thermal and electrochemical stability for practical device operation

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If wet film formation method is used to simplify manufacturing process, then manufacturing complexity is reduced, but driving stability deteriorates due to material impurities and crystallization

Engineering Contradiction:

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent controls molecular weight and purity parameters of charge transport materials to prevent crystallization during wet film formation, ensuring amorphous film formation that maintains device stability while utilizing the manufacturing simplicity of wet processing

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent develops composite charge transport materials with specific functional group combinations that provide both solubility in non-halogenated solvents and resistance to crystallization, enabling stable wet-formed films

Inventive Principle:

Principle #40Composite materials

4Ease of manufacture

If conventional charge transport materials are used to achieve acceptable performance, then device fabrication is simplified, but luminescent efficiency and triplet excitation level deteriorate

Engineering Contradiction:

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

The patent introduces specific functional groups and molecular structures in charge transport materials that enhance triplet excitation levels and luminescent efficiency while maintaining compatibility with conventional wet film formation processes, achieving both improved performance and manufacturing simplicity

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 monoamine compound facilitates the production of organic electroluminescent elements with high luminescent efficiency and driving stability, suitable for large-area films and various applications, including displays and lighting, while maintaining excellent film-forming and charge-transporting properties.

Implementation Method 1

As charge transport materials having the property of transporting holes

Methodology Applied

Scientific EffectCharge transport: Conduction (electrical)

Implementation Method 2

an organic electroluminescent element which utilizes phosphorescence so as to have enhanced luminescent efficiency

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Implementation Method 3

a wet film formation method has advantages, for example, that no vacuum process is necessary and film formation in a larger area is easy

Methodology Applied

Scientific EffectWet film formation: Deposition (physical)

Data Source

PatentEP3121165B1Monoamine compound, charge transport material, composition for charge transport film, organic electroluminescent element, organic el display device, and organic el lighting

Publication Date: 2019.04.17

Figure 1

AI summary

A monoamine compound represented by the following general formula (1): wherein R1 to R3 each independently represent a phenyl group which may have only one substituent in at least one of o- and m-positions, in which the substituent may be bonded to each other to form a cyclic structure, and R1 to R3 are a group different from each other, with the proviso that the monoamine compound is not represented by either one of the following structural formulas: