Composite Cathode Electrode Voltage Drop Reduction

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Solution Overview

Problem

Organic EL display units with top emission methods face challenges in achieving uniform emission luminance due to uneven voltage distribution across the cathode electrode, leading to variations in display quality, and the addition of auxiliary wiring on the same layer as the anode or driving element compromises the aperture ratio and manufacturing simplicity.

Innovation Solution

A display unit design featuring an organic layer between the first and second electrode layers, with an aperture-defining insulating film and a thicker gap section in the second electrode layer to reduce voltage drop, and auxiliary wiring connected to the second electrode layer to compensate for voltage drops without occupying space that would reduce the aperture ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If an optically transparent conductive material is used for the cathode electrode to enable light extraction, then light emission is achieved, but the high resistivity causes uneven voltage distribution and luminance variation

Engineering Contradiction:

Improvelight emissionVSAvoidvoltage uniformity

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent combines the transparent conductive layer (ITO) with a reflective metal layer (Aluminum) to form a composite cathode electrode structure. This merging allows the electrode to simultaneously achieve light extraction through the transparent layer and low resistance electrical conduction through the metal layer, resolving the contradiction between light emission and voltage uniformity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The cathode electrode is constructed as a composite material system consisting of an optically transparent conductive oxide layer (such as ITO with thickness 50-200 nm) combined with a highly conductive reflective metal layer (such as Aluminum with thickness 50-200 nm). This composite structure integrates the optical transparency needed for light extraction with the electrical conductivity required for uniform voltage distribution.

Inventive Principle:

Principle #40Composite materials

2Reliability

If auxiliary wiring is added on the same layer as the anode or driving element to compensate voltage drop, then voltage uniformity is improved, but the aperture ratio is reduced

Engineering Contradiction:

Improvevoltage uniformityVSAvoidaperture ratio

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent extracts the voltage compensation function from the display layer structure by implementing it in the cathode electrode itself through the reflective metal layer design. The metal layer naturally provides low resistance pathways that compensate for voltage drops without requiring separate auxiliary wiring structures, thus maintaining high aperture ratio while ensuring voltage uniformity.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The reflective metal layer in the cathode electrode serves multiple functions simultaneously: it provides electrical conduction for voltage uniformity, acts as a reflector to enhance light extraction efficiency, and eliminates the need for separate auxiliary wiring. This multi-functionality resolves the contradiction between voltage compensation and aperture ratio maintenance.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Area of stationary object

If the cathode electrode is made as an integrated layer to ensure high aperture ratio, then manufacturing is simplified, but voltage drop occurs across the electrode

Engineering Contradiction:

Improveaperture ratioVSAvoidvoltage uniformity

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The integrated cathode electrode is constructed as a composite of transparent conductive oxide and reflective metal layers. This composite structure maintains the simplicity of an integrated layer design while the metal component provides sufficient electrical conductivity to prevent voltage drop, simultaneously achieving high aperture ratio and voltage uniformity.

Inventive Principle:

Principle #40Composite 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 enhances uniformity in emission luminance and maintains a high aperture ratio, improving display performance while simplifying the structure and manufacturing process.

Implementation Method 1

an organic EL display unit has been put into practical use that utilizes a self-emitting type organic EL (Electro Luminescence) element including an organic layer

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

the thickness of the gap section portion of the second electrode layer is greater than the thickness of the light-emitting section portion of the second electrode layer

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Data Source

PatentUS9082733B2Display unit and electronic apparatus

Publication Date: 2015.07.14 MAGNOLIA BLUE CORP

AI summary

A display unit comprising an organic layer between a light-emitting section portion of a first electrode layer and a light-emitting section portion of a second electrode layer. Light is emissible from within the organic layer. An aperture-defining insulating film is between a contact section of the first electrode layer and a gap section portion of the second electrode layer. The thickness of the gap section portion of the second electrode layer is greater than the thickness of the light-emitting section portion of the second electrode layer.