Organic Light-Emitting Device Intermediate Layer Electron Injection

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Solution Overview

Problem

Organic light-emitting devices face reduced lifespans due to inefficient electron injection from the electron transport region to the emission layer, leading to charge accumulation at the interface, which deteriorates the device.

Innovation Solution

Incorporating an intermediate layer between the emission layer and the electron transport region, with specific compounds that control electron injection, exciton concentration, and distribution, ensuring efficient electron mobility and energy level alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electrons are injected from the electron transport region to the emission layer, then light emission is achieved, but charge accumulation occurs at the interface which deteriorates the device and reduces lifespan

Engineering Contradiction:

Improvedevice lifespanVSAvoidcharge accumulation at interface

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

An intermediate layer is introduced between the emission layer and the electron transport region to act as a mediator. This intermediate layer prevents direct contact between the emission layer and electron transport region, thereby eliminating charge accumulation at the interface while still allowing efficient electron injection. The intermediate layer serves as a buffer that manages charge distribution and prevents harmful accumulation effects.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electron transport region is divided into two separate regions: a first electron transport region adjacent to the emission layer and a second electron transport region adjacent to the cathode. This segmentation allows independent optimization of each region's properties. The first electron transport region is designed for efficient electron injection into the emission layer, while the second region handles electron transport to the cathode, preventing charge accumulation at the critical interface.

Inventive Principle:

Principle #1Segmentation

2Reliability

If an intermediate layer is added between the emission layer and electron transport region, then electron injection is controlled and lifespan is improved, but device structure becomes more complex

Engineering Contradiction:

Improvedevice lifespanVSAvoidlayer structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The intermediate layer is designed to perform multiple functions simultaneously: it controls electron injection from the electron transport region to the emission layer, manages exciton concentration and distribution in the emission layer, and prevents charge accumulation at the interface. By consolidating these multiple functions into a single layer, the design avoids the need for additional separate components, thereby limiting the increase in device complexity while achieving improved reliability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Productivity

If electron mobility is increased in the electron transport region, then electron injection efficiency is improved, but charge accumulation may occur if not properly managed

Engineering Contradiction:

Improveelectron injection efficiencyVSAvoidcharge accumulation

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

Different electron mobility characteristics are assigned to different regions. The first electron transport region (adjacent to the emission layer) is designed with specific electron mobility properties optimized for efficient electron injection, while the second electron transport region (adjacent to the cathode) has different properties optimized for electron transport to the cathode. This local optimization allows high electron injection efficiency without causing charge accumulation, as each region is tailored to its specific function.

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 enhances the lifespan of organic light-emitting devices by optimizing electron injection and exciton management, improving the overall performance and longevity of the device.

Implementation Method 1

Carriers, such as holes and electrons, recombine in the emission layer to produce excitons. These excitons transit from an excited state to a ground state, thereby generating light.

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

the third compound is a thermally activated delayed fluorescence compound or a phosphorescent metal complex

Methodology Applied

Scientific EffectPhosphorescence: Phosphorescence

Implementation Method 3

electrons provided from the second electrode may move toward the emission layer through the electron transport region

Methodology Applied

Scientific EffectElectron transport: Conduction (electrical)

Implementation Method 4

Carriers, such as holes and electrons, recombine in the emission layer to produce excitons. These excitons transit from an excited state to a ground state, thereby generating light.

Methodology Applied

Scientific EffectExciton recombination:

Data Source

PatentUS20210074940A1Organic light-emitting device and apparatus including the same

Publication Date: 2021.03.11 SAMSUNG DISPLAY CO LTD

AI summary

Organic light-emitting devices and apparatuses including the same have improved lifespans due to certain, defined material conditions and compositions.