OLED Encapsulation Structure with Dielectric SPP Coupling

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Solution Overview

Problem

Top-emitting OLED devices suffer from low optical efficiency due to significant light loss caused by surface plasmon polaritons (SPPs) at the cathode layer, resulting in only about 20% of light being coupled out, leading to inefficient light emission.

Innovation Solution

An encapsulation structure is introduced with a first inorganic dielectric layer attached to the cathode layer, where the dispersion relation among the dielectric layer, cathode layer, and electron injection layer is optimized to couple surface plasmon polaritons, enhancing light out-coupling efficiency by reducing SPP loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a conventional encapsulation structure is used for top-emitting OLED devices, then the device structure is simple and easy to manufacture, but the optical efficiency is low due to significant light loss caused by surface plasmon polaritons at the cathode layer

Engineering Contradiction:

Improvelight lossVSAvoidencapsulation structure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

An inorganic dielectric layer is introduced as an intermediary between the cathode layer and the electron injection layer. This intermediate layer mediates the interaction between SPPs at the two interfaces, enabling coupling of the plasmon modes and conversion of trapped light energy into extractable light, thereby reducing overall light loss without fundamentally redesigning the encapsulation structure

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The refractive index parameter of the dielectric layer is specifically selected to satisfy the dispersion relation condition that couples SPPs at the cathode-dielectric interface and the dielectric-electron injection interface. By changing this optical parameter, the system transforms from a state of high light loss to a state where light is effectively coupled and extracted

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the dispersion relation is optimized to couple surface plasmon polaritons, then the light out-coupling efficiency is improved by 40%, but the encapsulation structure becomes more complex with additional inorganic dielectric layer

Engineering Contradiction:

Improvelight out-coupling efficiencyVSAvoidencapsulation structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The inorganic dielectric layer serves multiple functions simultaneously: it acts as an optical coupling layer to enhance light extraction, provides encapsulation protection for the cathode layer, and maintains structural integrity of the device. This multi-functionality allows the additional layer to contribute to both improved productivity and structural necessity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The encapsulation structure employs a composite design combining organic encapsulation layers with inorganic dielectric layers. This composite structure leverages the advantages of both material types: the organic layers provide flexibility and conformal coverage, while the inorganic layers provide optical coupling enhancement and environmental barrier properties

Inventive Principle:

Principle #40Composite materials

3Loss of energy

If multiple encapsulation layers are added to improve optical efficiency, then the light extraction is enhanced, but the thickness of thin film layers increases

Engineering Contradiction:

Improvelight lossVSAvoidthin film layer thickness

Core Design Contradiction:

Loss of energyVSLength of stationary object

Solution Approach 1:

The inorganic dielectric layer is strategically positioned only at the cathode interface where SPP coupling is needed to enhance light extraction. This localized approach addresses the light loss problem at the critical interface without adding thickness throughout the entire device structure, maintaining local optimization without global thickening

Inventive Principle:

Principle #3Local quality

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

The encapsulation structure improves light out-coupling efficiency by 40%, increasing the optical efficiency of the electroluminescent device while maintaining moisture and oxygen resistance, and reduces the thickness of thin film layers.

Implementation Method 1

the optical parameter is related to dispersion and is configured to couple surface plasmon polaritons (SPPs) on interfaces of two sides of the cathode layer

Methodology Applied

Scientific EffectSurface plasmon polaritons (SPPs):

Data Source

PatentUS12379528B2Encapsulation structure, encapsulation method, electroluminescent device, and display device

Publication Date: 2025.08.05 BOE TECHNOLOGY GROUP CO LTD

AI summary

Provided is an encapsulation structure which is applicable for encapsulating an electroluminescent device, and includes: a first inorganic dielectric layer provided with a surface for being attached to a surface of a cathode layer of the electroluminescent device; wherein a dispersion relation among the first inorganic dielectric layer, the cathode layer and an electron injection layer of the electroluminescent device satisfies a preset condition, wherein the preset condition is configured to define an optical parameter of a first interface, the optical parameter is related to dispersion and is configured to couple surface plasmon polaritons (SPPs) on interfaces of two sides of the cathode layer, and the first interface is an interface between the first inorganic dielectric layer and the cathode layer.