Stacked OLED Charge Generation Layer Electron Injection

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Solution Overview

Problem

Existing stacked organic light-emitting diodes face challenges in achieving effective electron injection, particularly in inverted-type configurations, where the lower electrode is a cathode, due to limitations in charge generation and material layer interactions.

Innovation Solution

A charge generation layer comprising a first material layer with high electrical conductivity and a second material layer with lower conductivity, made from metal and organic materials respectively, is used, allowing for improved electron injection by reacting the electron injection layer with the second material layer, even in inverted-type configurations, and an organic layer is introduced to enhance this interaction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a charge generation layer with various material layers is used to generate charge, then charge injection into light-emitting units is improved, but device complexity increases

Engineering Contradiction:

Improvecharge injection effectivenessVSAvoidcharge generation layer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The charge generation layer is segmented into three distinct sub-layers: a first material layer adjacent to the electron injection layer, an electron injection layer in the middle, and a second material layer adjacent to the organic light-emitting layer. This segmentation allows each sub-layer to be optimized for its specific function, improving charge injection effectiveness while maintaining manageable complexity through functional specialization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different material compositions are assigned to different locations within the charge generation layer. The first material layer uses materials with specific electron mobility characteristics, the electron injection layer uses materials optimized for electron injection, and the second material layer uses materials that interface well with the organic light-emitting layer. This local optimization of material properties enhances overall charge injection performance.

Inventive Principle:

Principle #3Local quality

2Reliability

If material layers are made thicker to improve charge generation, then charge injection is enhanced, but sideward electrical conductivity issues arise

Engineering Contradiction:

Improvecharge generation efficiencyVSAvoidsideward electrical conductivity

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

Instead of increasing the thickness of individual material layers, the solution transitions to a multi-layer vertical structure where charge generation and injection occur through the vertical stacking of thin layers. This dimensional approach allows sufficient charge generation through the stacked configuration without any single layer becoming thick enough to cause sideward electrical conductivity problems.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If an inverted-type configuration is used with lower electrode as cathode, then device structure flexibility is improved, but electron injection effect deteriorates

Engineering Contradiction:

Improvedevice configuration flexibilityVSAvoidelectron injection effect

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The charge generation layer structure with the three-sub-layer configuration is designed to be universal and effective for both conventional and inverted-type OLED configurations. The electron injection layer is positioned centrally and can effectively inject electrons regardless of whether the lower electrode is the cathode (inverted-type) or the upper electrode is the cathode (conventional type), making the structure adaptable to different device architectures while maintaining reliable electron injection.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 achieves excellent electron injection effects, improving the quality of the display device by ensuring effective charge transfer and uniformity in the material layers, while avoiding issues related to thick material layers and sideward electrical conductivity.

Implementation Method 1

the first material layer (1071) with high electrical conductivity and a second material layer (1073) with lower conductivity

Methodology Applied

Scientific EffectElectrical conductivity: Conduction (electrical)

Data Source

PatentEP3070759B1Stacked organic light-emitting diode and preparation method therefor, and display device

Publication Date: 2022.01.12 BOE TECHNOLOGY GROUP CO LTD

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AI summary

A stacked organic light-emitting diode (100), a display device and a manufacturing method of a stacked organic light-emitting diode (100) are disclosed. A stacked organic light-emitting diode (100) includes at least two light-emitting units (103) in a stacked arrangement and a charge generation layer (107) disposed between the adjacent light-emitting units (103), wherein the charge generation layer (107) includes a first material layer (1071), an electron injection layer (1072) disposed on the first material layer (1071) and a second material layer (1073) disposed on the electron injection layer (1072). By means of said stacked organic light-emitting diode (100) and manufacturing method thereof, it can achieve excellent electron injection effect, even in the case of manufacturing an inverted-type stacked organic light-emitting diode (the lower electrode is a cathode).