Organic Electroluminescent Device Protrusion Interface

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Solution Overview

Problem

Existing organic electroluminescent devices (OELDs) suffer from significant light loss due to total reflection and surface plasmon resonance at interfaces with different refractive indices, leading to reduced luminance efficiency and shorter device lifetime.

Innovation Solution

The OELD structure is enhanced by forming protrusions on the organic light emitting layer with a pitch and height of 50 to 600 nm, and a metal cathode electrode is stacked to cover these protrusions, creating a corrugated interface that reduces light absorption and enhances light reflection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a planar structure with flat interfaces is used between layers, then the device structure is simple and easy to manufacture, but approximately 40% of visible light is lost at the interface between the organic light emitting layer and the anode electrode due to total reflection

Engineering Contradiction:

Improvelight loss at interfaceVSAvoidinterface structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies curvature by forming protrusions (convex structures) on the organic light emitting layer instead of using a flat planar interface. These protrusions have curved surfaces that reduce total internal reflection at the interface between layers with different refractive indexes, thereby reducing light loss while maintaining manufacturing feasibility through deposition processes

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Loss of energy

If a flat interface between the organic light emitting layer and the cathode electrode is used, then the device structure is simple, but another 40% of visible light is absorbed by the cathode electrode and converted to heat due to surface plasmon resonance

Engineering Contradiction:

Improvelight absorption by cathodeVSAvoidinterface structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies curvature by forming protrusions on the organic light emitting layer that extend toward the cathode electrode, creating a non-planar interface. This curved geometry reduces the contact area between the emitting layer and the metal cathode, thereby minimizing surface plasmon resonance and light absorption by the cathode electrode

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Productivity

If protrusions with pitch and height of 50 to 600 nm are formed on the organic light emitting layer, then luminance efficiency is increased by reducing light loss, but the manufacturing process becomes more complex requiring porous masks and multiple deposition steps

Engineering Contradiction:

Improveluminance efficiencyVSAvoidmanufacturing process

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent employs porous masks containing regularly arranged pores with specific dimensions to form protrusions on the organic light emitting layer. The porous structure allows selective deposition of organic material through the pores, creating the desired protrusion pattern. This approach enables precise control of protrusion pitch and height while using standard deposition equipment, balancing manufacturing complexity with luminance efficiency improvement

Inventive Principle:

Principle #31Porous 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 increases luminance efficiency and extends the device's lifetime by minimizing light loss and reducing energy input, while maintaining high display characteristics.

Implementation Method 1

forming plurality of the protrusions on an upper surface of the base layer by depositing an organic light emitting material through the plurality of pores of the porous mask

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

forming an aluminum oxide layer in which a plurality of pores are formed by anodizing a surface of the aluminium substrate

Methodology Applied

Scientific EffectAnodizing: Anodising

Implementation Method 3

a portion of visible light emitted from the organic light emitting layer 14 is lost at an interface between the organic light emitting layer 14 and the anode electrode 12 due to a total reflection at the interface

Methodology Applied

Scientific EffectTotal Internal Reflection: Total Internal Reflection

Implementation Method 4

another 40% of visible light is absorbed by the cathode electrode 16 and absorbed as heat due to a surface plasmon resonance (SPR) phenomenon occurring at a flat interface between the organic light emitting layer 14 and the cathode electrode 16

Methodology Applied

Scientific EffectSurface Plasmon Resonance: Resonance

Data Source

PatentUS8038494B2Organic electroluminescent device and method of manufacturing the same

Publication Date: 2011.10.18 SAMSUNG DISPLAY CO LTD

AI summary

An organic electroluminescent device (OELD) and a method of manufacturing the OELD are provided. The OELD includes a substrate, an anode electrode stacked on the substrate, an organic light emitting layer that is stacked on the anode electrode and has a plurality of protrusions on the organic light emitting layer, and a cathode electrode that covers the protrusions formed on the organic light emitting layer and is formed of a metal.