Organic Electroluminescent Device With LEL Hole Blocking

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Solution Overview

Problem

Existing organic electroluminescent devices face challenges in achieving high efficiency, low voltage, and long lifetime, particularly in blue phosphorescent devices, due to issues with hole diffusion and recombination, which affect color purity and durability.

Innovation Solution

Incorporating a lifetime enhancement layer (LEL) composed of a bipolar compound with specific properties, including an electron withdrawal group and an electron donor group, to prevent hole diffusion and enhance exciton formation efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a multilayer-laminated structure is used to improve device performance and lifetime, then light emitting efficiency and commercialization characteristics are achieved, but hole diffusion into the electron transporting layer occurs, reducing device lifetime

Engineering Contradiction:

Improvedevice lifetimeVSAvoidhole diffusion

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

A hole blocking layer is introduced as an intermediary component between the light emitting layer and the electron transporting layer. This layer specifically blocks hole diffusion into the electron transporting layer while maintaining electron transport, thereby preventing the harmful effect of hole diffusion without compromising the overall device performance and lifetime

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electron transporting layer is divided into two separate layers: a first electron transporting layer adjacent to the light emitting layer, and a second electron transporting layer adjacent to the electron injection layer. This segmentation allows the first layer to focus on blocking hole diffusion while the second layer focuses on electron injection, thereby resolving the contradiction between preventing hole diffusion and maintaining electron transport

Inventive Principle:

Principle #1Segmentation

2Manufacturing precision

If the number of pixels is increased to achieve high resolution, then display resolution is improved, but the light emitting area of each pixel decreases, reducing device lifetime

Engineering Contradiction:

Improvedisplay resolutionVSAvoiddevice lifetime

Core Design Contradiction:

Manufacturing precisionVSDuration of action of stationary object

Solution Approach 1:

The hole blocking layer serves as a protective intermediary that prevents hole diffusion into the electron transporting layer, thereby protecting the device structure from degradation even when the light emitting area is reduced due to high pixel density, thus maintaining device lifetime despite increased resolution requirements

Inventive Principle:

Principle #24Intermediary (Mediator)

3Use of energy by moving object

If phosphorescent dopant with heavy atoms is used to improve light emitting efficiency, then internal quantum efficiency increases up to 4 times, but device complexity and material requirements increase

Engineering Contradiction:

Improvelight emitting efficiencyVSAvoidmaterial requirements

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The invention changes the structural parameter of the electron transporting layer by dividing it into two layers with different functional focuses. This structural parameter change allows the use of phosphorescent dopants with heavy atoms to achieve high light emitting efficiency while managing material requirements through optimized layer configuration and hole blocking functionality

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 LEL improves the lifetime and stability of the organic electroluminescent device by blocking hole diffusion, enhancing exciton formation, and maintaining efficient light emission.

Implementation Method 1

the lifetime enhancement layer (LEL) includes a bipolar compound having both an electron withdrawal group (EWG) with a high electron absorption property and an electron donor group (EDG) with a high electron donor property

Methodology Applied

Scientific EffectHole blocking:

Implementation Method 2

When the injected holes and electrons meet each other, an exciton is formed, and the exciton falls down to a bottom state to emit light

Methodology Applied

Scientific EffectExciton formation:

Implementation Method 3

Studies on an organic electroluminescent (EL) device have continued to blue electric light emission using an anthracene single crystal in 1965

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS12441935B2Organic electroluminescent device

Publication Date: 2025.10.14 SOLUS ADVANCED MATERIALS CO LTD

AI summary

The present disclosure provides an organic electroluminescent device including: an anode; a cathode; and one or more organic material layers interposed between the anode and cathode and selected from the group consisting of a hole injection layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and an electron injection layer, and further including a lifetime enhancement layer (LEL) between the light emitting layer and the electron transporting layer.