Multilayer Electrode Structure for Light-Emitting Element Voltage Loss Reduction

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Solution Overview

Problem

Conventional light-emitting elements have insufficient element characteristics, particularly high driving voltage due to voltage loss and poor charge injection characteristics at the electrodes, which hinders efficient light emission and power consumption.

Innovation Solution

A light-emitting element structure comprising a first conductive layer of aluminum, a second conductive layer of titanium, and a third conductive layer of indium oxide or zinc oxide, with the third layer having a higher work function than the first layer, reduces voltage loss and enhances charge injection, thereby lowering the driving voltage and improving light emission intensity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a conventional electrode structure is used, then the manufacturing process is simple, but the voltage loss is high and charge injection characteristics are poor

Engineering Contradiction:
Improvevoltage lossVSAvoidelectrode structure complexity
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The electrode is divided into multiple conductive layers (first conductive layer, second conductive layer, third conductive layer) with different materials and functions. Each layer segment addresses specific issues: the first layer provides basic conductivity, the second layer improves adhesion and reduces oxidation, and the third layer enhances charge injection characteristics, collectively reducing voltage loss

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The electrode uses composite material structure combining different conductive materials in specific layers. This composite approach optimizes both electrical properties (charge injection) and mechanical properties (adhesion), resolving the contradiction between energy loss reduction and structural complexity

Inventive Principle:
Principle #40Composite materials

2Use of energy by moving object

If the driving voltage is reduced, then power consumption decreases, but light emission intensity may be affected

Engineering Contradiction:
Improvepower consumptionVSAvoidlight emission intensity
Core Design Contradiction:
Use of energy by moving objectVSIllumination intensity

Solution Approach 1:

The invention changes the work function parameters of the conductive layers by selecting specific materials with appropriate work functions. The third conductive layer has a higher work function than the first layer, creating optimal electron injection conditions that enable efficient light emission at reduced driving voltages

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

Different regions of the electrode structure have different local properties optimized for specific functions. The third conductive layer specifically targets charge injection enhancement, while the overall structure maintains low voltage operation, allowing both reduced power consumption and sufficient light emission intensity

Inventive Principle:
Principle #3Local quality

3Illumination intensity

If aluminum is used as the first conductive layer, then reflectivity is high, but adhesion to subsequent layers is insufficient

Engineering Contradiction:
Improvelight reflectivityVSAvoidadhesion strength
Core Design Contradiction:
Illumination intensityVSStrength

Solution Approach 1:

The second conductive layer acts as an intermediary between the aluminum first layer and the third conductive layer. This intermediate layer improves adhesion to the aluminum surface while also preventing oxidation, thereby maintaining both the high reflectivity of the aluminum layer and achieving sufficient adhesion strength

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The adhesion and oxidation resistance functions are extracted from the aluminum layer itself and assigned to a separate second conductive layer. This allows the aluminum layer to focus on providing high reflectivity while the second layer专门 handles adhesion and oxidation protection

Inventive Principle:
Principle #2Taking out (Extraction)

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 proposed structure reduces driving voltage, enhances light emission intensity, and improves overall element characteristics, leading to more efficient and power-efficient light-emitting devices.

Implementation Method 1

the third conductive layer is capable of transmitting light

Methodology Applied
Scientific EffectLight transmission:

Implementation Method 2

a first conductive layer reflecting light

Methodology Applied
Scientific EffectLight reflection: Reflection

Implementation Method 3

a light-emitting layer overlapping with the first electrode and the second electrode and emits light in accordance with voltage applied between the first electrode and the second electrode

Methodology Applied
Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 4

wherein part of the second conductive layer is oxidized

Methodology Applied
Scientific EffectOxidation: Oxidation

Data Source

PatentEP2487733B1Light-emitting element, display device, lighting device, and method for manufacturing the same
Publication Date: 2020.01.22 SEMICON ENERGY LAB CO LTD
  • EP2487733B1 patent drawingFigure 1A~1B
  • EP2487733B1 patent drawingFigure 2A~2E
  • EP2487733B1 patent drawingFigure 3A~3D

AI summary

A light-emitting element disclosed includes a first electrode layer (101); a second electrode layer (103) which transmits light; and a light-emitting layer (102) interposed between the first electrode layer (101) and the second electrode layer (103). The first electrode layer (101) includes a first conductive layer (111) which is able to reflect light, a second conductive layer (112) provided over the first conductive layer (111) and including titanium, and a third conductive layer (113) which transmits light and contains a metal oxide having work function higher than that of a material of the first conductive layer (111).