OLED Tandem Structure Fullerene Lithium Quinolate Electron Injection Layer

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Solution Overview

Problem

Organic light emitting diode (OLED) display devices face challenges in achieving a low driving voltage and improved lifespan while maintaining efficient light emission, particularly in tandem structures where the number of layers increases the driving voltage and affects the durability of fullerene-based electron injection layers.

Innovation Solution

The organic light emitting element incorporates a tandem structure with a lithium quinolate-containing first electron injection layer and a fullerene-containing second electron injection layer, eliminating the need for a charge generation layer to reduce driving voltage and enhance lifespan, and includes a hole transport layer doped with a P-type material to facilitate efficient electron transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a tandem structure is used to improve luminance efficiency, then luminance efficiency is improved, but driving voltage increases

Engineering Contradiction:

Improveluminance efficiencyVSAvoiddriving voltage

Core Design Contradiction:

Use of energy by moving objectVSPower

Solution Approach 1:

An electron injection layer comprising fullerene and lithium quinolate is introduced as an intermediary between the first emission layer and the second emission layer in the tandem structure. This intermediary layer facilitates efficient electron injection and transfer between the two emission layers, enabling high luminance efficiency while maintaining low driving voltage through improved charge transport rather than increased power input

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If the number of layers is increased to improve light emission efficiency, then light emission efficiency is improved, but lifespan decreases

Engineering Contradiction:

Improvelight emission efficiencyVSAvoidlifespan

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The electron injection layer acts as a protective intermediary that shields the fullerene-based materials from degradation by facilitating controlled electron transfer. This intermediary function allows the tandem structure to maintain high light emission efficiency while the electron injection layer protects the organic materials from oxidative degradation, thereby extending device lifespan

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The electron injection layer modifies the energy level parameters and electron affinity characteristics at the interface between emission layers. By optimizing the HOMO and LUMO levels through the combination of fullerene and lithium quinolate, the device achieves efficient electron injection without excessive energy input, reducing stress on the organic materials and improving operational stability and lifespan

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a charge generation layer is eliminated to reduce device complexity, then device complexity is reduced, but electron transfer efficiency may be affected

Engineering Contradiction:

Improvedevice complexityVSAvoidelectron transfer efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The functions of the charge generation layer and electron injection layer are merged into a single electron injection layer comprising fullerene and lithium quinolate. This combined layer performs both charge generation and electron injection functions, eliminating the need for a separate charge generation layer while maintaining efficient electron transfer between the two emission layers in the tandem structure

Inventive Principle:

Principle #5Merging (Combining)

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 results in a lower driving voltage and improved lifespan of the organic light emitting element, with enhanced luminance efficiency and reduced masking processes required for color emission, while maintaining the advantages of a self-emitting type display.

Implementation Method 1

an electron injection layer (EIL) between the first emission layer and the second emission layer, and including fullerene (C60)... a lithium quinolate (LiQ)-containing first electron injection layer (EIL) and a fullerene (C60)-containing second electron injection layer (EIL)

Methodology Applied

Scientific EffectElectron transfer: Conduction (electrical)

Implementation Method 2

The organic light emitting element utilizes a principle that excitons are generated by the binding (or recombination) of electrons and holes in an organic emission layer between the two electrodes when electrons and holes are injected into the organic emission layer from the two electrodes. Thus, light is generated when the excitons fall from an excited state to a ground state.

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS9293736B2Organic light emitting element having emission layers and an electron injection layer including fullerene and lithium quinolate

Publication Date: 2016.03.22 SAMSUNG DISPLAY CO LTD

AI summary

An organic light emitting element includes a first electrode, a second electrode, and an organic layer. The organic layer includes a first emission layer between the first electrode and the second electrode, a second emission layer between the first emission layer and the second electrode, and an electron injection layer (EIL) between the first emission layer and the second emission layer, the electron injection layer (EIL) containing fullerene (C60).