Stacked OLED Charge Generation Layer Stability

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Organic electroluminescent devices face limitations in practical use due to short lifetime and low initial brightness, which is exacerbated by instability in electron injection layers and low efficiency of charge generation layers, particularly when using materials like BCP and metal oxides.

Innovation Solution

The use of charge generation layers composed of alkali metals and alkaline earth metals, or their fluorides, between light-emitting units in a stacked display device configuration, improves charge injection efficiency and stability, enhancing brightness and long-term reliability without requiring precise stoichiometric control during fabrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If BCP and metal oxide are used in electron injection layer and charge generation layer, then charge injection efficiency is improved, but material stability and environmental reliability deteriorate

Engineering Contradiction:

Improvecharge injection efficiencyVSAvoidmaterial stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent replaces unstable but high-performance materials (BCP, metal oxides) with stable organic compounds that have sufficient charge injection efficiency. This substitution prioritizes long-term stability over maximum initial efficiency, accepting a moderate performance trade-off for reliable operation.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent modifies the chemical composition parameters of the charge generation layer by using organic compounds with specific molecular structures (formula 1) that balance stability and charge injection capability. This parameter change allows the material to maintain composition stability while achieving acceptable charge injection efficiency.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If precise stoichiometric ratio control is implemented during fabrication, then charge generation layer performance is optimized, but manufacturing complexity and process difficulty increase

Engineering Contradiction:

Improvecharge generation layer performanceVSAvoidfabrication process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses organic compounds that are inherently tolerant to stoichiometric variations, eliminating the need for precise ratio control during fabrication. This approach sacrifices optimal performance tuning for much simpler manufacturing processes.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the material parameters to use organic compounds with broad compositional tolerance windows, allowing fabrication without strict stoichiometric control while maintaining sufficient charge generation layer performance.

Inventive Principle:

Principle #35Parameter changes

3Duration of action of moving object

If drive current is reduced to extend device lifetime, then operational duration is improved, but initial brightness and practical applicability deteriorate

Engineering Contradiction:

Improvedevice lifetimeVSAvoidinitial brightness

Core Design Contradiction:

Duration of action of moving objectVSIllumination intensity

Solution Approach 1:

The patent uses stable organic compounds in the charge generation layer that enable extended device operation at reduced drive currents without significant performance degradation. This stability allows the device to maintain acceptable brightness levels over longer operational periods.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent modifies the material composition to achieve better efficiency in charge generation, allowing the device to operate at lower currents while maintaining brightness. This parameter change in material properties enables extended lifetime without severe brightness penalty.

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

This configuration doubles or triples the brightness of organic electroluminescent devices while maintaining efficiency, and significantly improves long-term reliability and environmental stability, simplifying the fabrication process by eliminating the need for precise stoichiometric ratio management.

Implementation Method 1

light produced upon recombination of electrons injected from the cathode and holes injected from the anode within the light-emitting layer 4c is outputted

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS7736754B2Display device

Publication Date: 2010.06.15 JDI DESIGN & DEV GK

AI summary

In a stacked display device with light-emitting units composed of organic layers and stacked together, the use of a stable material in at least a portion of a charge generation layer makes it possible to achieve improvements in environmental stability and also to attain an improvement in the efficiency of injection of charges from the charge generation layer into the light-emitting units. The display device can be readily fabricated. In a display device (11) provided with a plurality of light-emitting units (14-1)(14-2), each of which includes at least an organic light-emitting layer (14c), stacked together between a cathode (16) and an anode (13), and also with a charge generation layer (15) held between the respective light-emitting units (14-1)(14-2), at least a portion of the charge generation layer (15) is composed of an oxide or fluoride which contains at least one of alkali metals and alkaline earth metals.