Organic Electroluminescent Device Electron Buffer Layer

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Solution Overview

Problem

Existing organic electroluminescent devices face challenges with efficiency and lifespan due to issues with electron transport materials, particularly when using nitrogen-containing heteroaryl compounds, which result in lower LUMO energy levels and inappropriate electron transport properties.

Innovation Solution

Incorporating a specific combination of an electron buffer layer with a compound represented by formula 1 and an electron transport layer with a compound represented by formula 2, where the electron buffer layer is positioned between the light-emitting layer and the electron transport layer, optimizing the LUMO energy levels to enhance electron injection and recombination opportunities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional electron transport materials like Alq3 are used, then electron transport capability is improved, but color purity is reduced due to material migration to other layers

Engineering Contradiction:

Improveelectron transport capabilityVSAvoidcolor purity

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The patent introduces an electron buffer layer as an intermediary between the light-emitting layer and the electron transport layer. This buffer layer prevents direct contact and migration of electron transport materials to the light-emitting layer, thereby maintaining color purity while still enabling effective electron transport through the buffered interface.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electron transport function is segmented into two distinct layers: an electron buffer layer and an electron transport layer. The buffer layer handles the interface with the light-emitting layer to prevent migration, while the transport layer handles the bulk electron transport function, allowing each layer to be optimized for its specific function.

Inventive Principle:

Principle #1Segmentation

2Productivity

If fluorescent materials are used to improve efficiency, then device efficiency is reduced compared to phosphorescent materials

Engineering Contradiction:

Improveluminous efficiencyVSAvoiddevice efficiency

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the energy level parameters of the electron buffer layer, specifically optimizing its LUMO energy level to be between -2.0 eV and -3.0 eV. This parameter optimization enables better electron injection and energy management, allowing fluorescent materials to achieve efficiency levels comparable to or exceeding conventional phosphorescent materials.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If nitrogen-containing heteroaryl compounds are used as electron transport materials, then LUMO energy level is reduced, but electron transport properties become inappropriate

Engineering Contradiction:

ImproveLUMO energy levelVSAvoidelectron transport properties

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies local quality by using nitrogen-containing heteroaryl compounds specifically in the electron buffer layer rather than throughout the entire electron transport system. This localized application allows the buffer layer to benefit from the lower LUMO energy level for improved electron injection, while the main electron transport layer maintains appropriate transport properties through different material selection.

Inventive Principle:

Principle #3Local quality

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 configuration improves the efficiency and lifespan of organic electroluminescent devices by effectively managing electron flow and energy barriers, leading to higher luminous efficiency and longer device lifespan.

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

optimizing the LUMO energy levels to enhance electron injection and recombination opportunities

Methodology Applied

Scientific EffectEnergy level optimization:

Implementation Method 3

The organic light-emitting compound moves into an excited state by the energy and emits light from energy when the organic light-emitting compound returns to the ground state from the excited state

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 4

An organic EL device changes electric energy into light by the injection of a charge into an organic light-emitting material

Methodology Applied

Scientific EffectEnergy conversion:

Data Source

PatentUS11107997B2Organic electroluminescent device comprising an electron buffer layer and an electron transport layer

Publication Date: 2021.08.31 DUPONT SPECIALTY MATERIALS KOREA LTD

AI summary

The present disclosure relates to an organic electroluminescent device. The organic electroluminescent device of the present disclosure comprises a specific combination of an electron buffer material and an electron transport material which can provide high efficiency and/or long lifespan.