LED Hole Injection Layers with Inorganic Dipole Materials

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Solution Overview

Problem

Light emitting diodes (LEDs) have low emission efficiency, requiring high driving voltages that can shorten their lifespan and that of their host displays.

Innovation Solution

A light emitting diode structure is developed with a first electrode overlapping a second electrode, an emission layer, and hole injection and transporting layers, where each hole injection layer includes an inorganic dipole material and an organic material, and an electron injection layer containing a lanthanum element or alkali metal halide, enhancing efficiency and reducing driving voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional hole injection layers are used in LEDs, then the device structure is simple, but the emission efficiency is low and driving voltage is high

Engineering Contradiction:

Improveemission efficiencyVSAvoidhole injection layer structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The hole injection layer is divided into multiple distinct layers: a first hole injection layer adjacent to the first electrode, a second hole injection layer between the hole transporting layer and emission layer, and intermediate hole injection layers. Each layer uses different materials optimized for specific functions, resolving the contradiction by improving emission efficiency through functional segmentation while managing device complexity through systematic layer design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs composite material structures in the hole injection layers, combining organic materials (such as CuI, AgI, AuI) with inorganic dipole materials. This composite approach enhances emission efficiency by optimizing charge injection and transport properties while maintaining a manageable device structure through targeted material selection in each layer.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If high driving voltage is applied to achieve high luminance, then luminance is improved, but lifespan is shortened

Engineering Contradiction:

ImproveluminanceVSAvoidlifespan

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent changes the electrical parameters of the hole injection layers by introducing materials with optimized work functions and dipole moments. This allows achieving high luminance at reduced driving voltages, thereby extending LED lifespan. The intermediate hole injection layers specifically engineered with appropriate energy levels enable efficient charge injection without requiring excessive voltage.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Intermediate hole injection layers are introduced as mediator layers between the first and second hole injection layers. These intermediate layers facilitate smooth charge transfer and reduce energy barriers, enabling high luminance output at lower driving voltages, thus protecting the LED from voltage-induced degradation and extending operational lifespan.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Use of energy by moving object

If conventional materials are used in hole injection layers, then manufacturing is simpler, but power efficiency is lower

Engineering Contradiction:

Improvepower efficiencyVSAvoidmanufacturing complexity

Core Design Contradiction:

Use of energy by moving objectVSEase of manufacture

Solution Approach 1:

The patent applies local quality optimization by selecting specific materials for specific layers based on their functional requirements. The first hole injection layer uses materials optimized for electrode interface compatibility, the second hole injection layer uses materials optimized for emission layer interface compatibility, and intermediate layers use materials optimized for charge transport. This localized material optimization improves power efficiency while maintaining manufacturing feasibility through standardized layer-by-layer fabrication processes.

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 solution improves light efficiency and extends the lifespan of LEDs by reducing the driving voltage, enhancing power efficiency and reliability, particularly in high-temperature environments like those experienced in vehicles exposed to strong sunlight.

Implementation Method 1

each of the first hole injection layer and the second hole injection layer includes an inorganic dipole material

Methodology Applied

Scientific EffectDipole effect:

Implementation Method 2

an emission layer between the first and second electrodes

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS11050035B2Light emitting diode and display device including the same

Publication Date: 2021.06.29 SAMSUNG DISPLAY CO LTD

AI summary

A light emitting diode includes a first electrode overlapping a second electrode, an emission layer between the first and second electrodes. a first hole injection layer and a second hole injection layer between the first electrode and the emission layer, and a first hole transporting layer between the first hole injection layer and the second hole injection layer. Each of the first and second hole injection layers includes an inorganic dipole material. At least one of the first hole injection layer or the second hole injection layer including an organic material.