Organic EL Display Cathode Oxidation Inhibiting Layer

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Solution Overview

Problem

Organic EL display devices with aluminum thin-films as cathodes suffer from performance degradation due to oxidation, leading to increased drive voltage and decreased luminance half-life in top-emission types.

Innovation Solution

Incorporating an oxidation inhibiting layer closer to the light-emitting layer and a cathode protecting layer further away, both stacked between the cathode and the sealing layer, to prevent oxidation of the cathode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If an aluminum thin-film is used as a cathode to transmit visible light, then light transmission performance is improved, but oxidation of the aluminum thin-film causes performance deterioration

Engineering Contradiction:

Improvelight transmissionVSAvoidcathode performance stability

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

An oxidation inhibiting layer is introduced as an intermediary between the aluminum cathode and the external environment. This layer acts as a mediator that prevents direct contact between oxygen and the aluminum thin-film, thereby eliminating the oxidation problem while maintaining the light transmission properties of the aluminum cathode.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The cathode structure is transformed from a single aluminum thin-film into a composite structure consisting of the aluminum thin-film stacked with an oxidation inhibiting layer. This composite structure combines the light transmission advantage of aluminum with the oxidation resistance of the inhibiting layer, resolving the contradiction between transmission performance and reliability.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If the cathode is exposed to oxygen environment, then manufacturing simplicity is improved, but oxidation occurs leading to increased drive voltage and decreased luminance half life

Engineering Contradiction:

Improvecathode fabrication simplicityVSAvoidluminance half life

Core Design Contradiction:

Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The oxidation inhibiting layer is formed in advance during the vacuum deposition process, before the cathode is exposed to the oxygen environment. This preliminary protective action ensures that the aluminum thin-film is already protected when it comes into contact with oxygen, preventing oxidation and maintaining long-term device performance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The cathode and oxidation inhibiting layer are formed in a vacuum environment, which is an inert atmosphere free of oxygen. This prevents oxidation during the manufacturing process, allowing the cathode to be fabricated with simplicity while ensuring long-term durability by eliminating oxidative degradation from the outset.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

3Reliability

If oxidation inhibiting layer and cathode protecting layer are stacked between cathode and sealing layer, then cathode oxidation is prevented, but device structure complexity increases

Engineering Contradiction:

Improvecathode oxidation resistanceVSAvoidlayer structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The thicknesses of the oxidation inhibiting layer and cathode protecting layer are optimized to minimum effective values. By carefully controlling the thickness parameters, the patent achieves sufficient oxidation protection while minimizing the additional structural complexity and maintaining a relatively simple overall device architecture.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite layer structure where the oxidation inhibiting layer and cathode protecting layer are deposited using standard vacuum deposition techniques. This approach integrates the protective function into the existing manufacturing process without requiring complex additional equipment or procedures, thus achieving improved reliability with minimal increase in device complexity.

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 reduces the increase in drive voltage and decrease in luminance half-life, enhancing the longevity and efficiency of the organic EL display device.

Implementation Method 1

an oxidation inhibiting layer and a cathode protecting layer are stacked between the cathode and the sealing layer, the oxidation inhibiting layer being closer to the light-emitting layer than the cathode protecting layer is

Methodology Applied

Scientific EffectOxidation inhibition: Oxidation

Implementation Method 2

forming an oxidation inhibiting layer above the cathode, the cathode and the oxidation inhibiting layer being sequentially formed in a vacuum

Methodology Applied

Scientific EffectVacuum deposition: Physical Vapour Deposition

Data Source

PatentUS9331297B2Organic EL display device and method for manufacturing same

Publication Date: 2016.05.03 MAGNOLIA BLUE CORP

AI summary

An organic EL display device comprising: an anode; a cathode that is a metal film; a light-emitting layer between the anode and the cathode; and a sealing layer that covers a side of the cathode opposite a side on which the light-emitting layer is provided. An oxidation inhibiting layer and a cathode protecting layer are stacked between the cathode and the sealing layer. The oxidation inhibiting layer is closer to the light-emitting layer than the cathode protecting layer is.