Light Emitting Element Mixed Electron Transport Layer

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Solution Overview

Problem

The existing light-emitting devices face a shortening of lifetime due to carrier imbalance and degradation in the organic layers, particularly in the light-emitting layer, leading to inefficient carrier injection and recombination.

Innovation Solution

A light-emitting element configuration is introduced with specific energy level differences between layers, including a mixed second electron transport layer with an electron-accepting material, and an interlayer organic layer with high electron mobility to improve carrier balance and reduce degradation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an interlayer film is inserted between organic layers to suppress degradation, then the light-emitting layer degradation is suppressed, but the lifetime of the light-emitting device is still shortened due to carrier accumulation

Engineering Contradiction:

Improvelight-emitting layer stabilityVSAvoiddevice lifetime

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The patent applies local quality by creating a mixed layer with specific composition (electron-accepting material at 5-50 at%) at the interface between the electron transport layer and light-emitting layer. This localized compositional modification addresses carrier accumulation specifically at the critical interface region without altering the overall device structure, thereby extending lifetime while maintaining stability.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the compositional parameter of the electron transport layer by incorporating electron-accepting materials at controlled concentrations (5-50 at%). This parameter modification adjusts the electron affinity and carrier distribution characteristics, preventing carrier accumulation and extending device lifetime while maintaining light-emitting layer stability.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If carrier injection efficiency is improved, then light emission efficiency is enhanced, but carrier imbalance and electron excess occur leading to degradation

Engineering Contradiction:

Improvelight emission efficiencyVSAvoidcarrier balance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent introduces a mixed layer containing electron-accepting materials as an intermediary between the electron transport layer and light-emitting layer. This intermediary component regulates electron flow by temporarily accepting and redistributing carriers, thereby maintaining carrier balance while preserving efficient light emission.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent employs composite materials by combining electron transport materials with electron-accepting materials in specific ratios (5-50 at%). This composite structure enables simultaneous achievement of high electron transport efficiency and balanced carrier distribution, preventing degradation while maintaining light emission efficiency.

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

This configuration enhances carrier injection efficiency, reduces electron excess, and extends the lifetime of the light-emitting element by maintaining stable carrier transport and recombination efficiency.

Implementation Method 1

a second electron transport layer (18) on the first electron transport layer (16), wherein the second electron transport layer (18) includes an organic material having electron transport properties

Methodology Applied

Scientific EffectElectron transport: Conduction (electrical)

Implementation Method 2

the second electron transport layer (18) includes an electron-accepting material and an organic material having electron transport properties, and includes the electron-accepting material at an amount greater than 50 mass %

Methodology Applied

Scientific EffectElectron acceptance: Absorption (physical)

Data Source

PatentUS20230134846A1Light emitting element and display device

Publication Date: 2023.05.04 SHARP KK

AI summary

A light-emitting element is provided with an interlayer organic layer having electron transport properties. At a HOMO level, an energy level difference between a first hole transport layer and the second hole transport layer is from 0.0 eV to 0.20 eV, and at a LUMO level, an energy level difference between a first electron transport layer and a second electron transport layer, and an energy level difference between the first electron transport layer and the blue light-emitting layer are each from 0.0 eV to 0.20 eV. Alternatively, the light-emitting element is provided with the interlayer organic layer between the electron transport layer and the cathode electrode, the electron transport layer is formed from a lithium quinolate complex and an organic compound having electron transport properties, and the interlayer organic layer is formed from an organic compound including an amino group or a hydroxyl group.