Inorganic Electron Transport Layer for OLED Hole Leakage

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Solution Overview

Problem

In OLED and QLED display devices, hole leakage into the electron transport layer reduces luminous and quantum efficiency, and requires higher driving voltages due to the relatively high HOMO energy level of organic materials used in the electron transport layer.

Innovation Solution

Incorporating an electron transport layer with inorganic particles of different average sizes, where the first particles have a higher energy bandgap and the second particles have a deeper LUMO energy level, to balance charge injection and prevent hole leakage, thereby improving luminous and quantum efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If an organic material with relatively high HOMO energy level is used in the electron transport layer, then charge transport is facilitated, but hole leakage into the electron transport layer increases and luminous efficiency decreases

Engineering Contradiction:

Improvecharge transportVSAvoidluminous efficiency

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The patent changes the energy level parameters of the electron transport layer by using inorganic materials with deeper HOMO and LUMO energy levels compared to organic materials. This parameter change creates an energy barrier that prevents hole leakage while maintaining electron transport capability, thereby resolving the contradiction between ease of charge transport and luminous efficiency

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures by combining inorganic electron transport materials with organic emitting materials in distinct layers. This composite approach allows each layer to perform its optimal function - the inorganic ETL provides deep energy levels for hole blocking while the organic EML provides efficient light emission, thus resolving the contradiction

Inventive Principle:

Principle #40Composite materials

2Ease of operation

If an organic material with relatively high HOMO energy level is used in the electron transport layer, then charge injection is improved, but driving voltage increases

Engineering Contradiction:

Improvecharge injectionVSAvoiddriving voltage

Core Design Contradiction:

Ease of operationVSPower

Solution Approach 1:

The patent changes the energy level parameters by selecting inorganic materials with deeper HOMO and LUMO levels. This creates an optimized energy gradient that facilitates charge injection from the electrode while preventing charge leakage into the ETL, thereby reducing the driving voltage required for efficient operation

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If inorganic particles with different average sizes are incorporated into the electron transport layer, then hole leakage is prevented and luminous efficiency is improved, but device structure becomes more complex

Engineering Contradiction:

Improveluminous efficiencyVSAvoidelectron transport layer structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies local quality by incorporating inorganic particles with different average sizes at specific locations within the electron transport layer. This creates localized variations in energy levels and charge transport properties, optimizing hole blocking and electron injection at different regions of the ETL while maintaining overall structural simplicity

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

This approach effectively injects charges into the emissive layer in a balanced manner, preventing hole leakage and enhancing luminous and quantum efficiency while reducing the driving voltage required for light emission.

Implementation Method 1

an electron transport layer adjacent to the emitting material layer, wherein the electron transport layer includes a plurality of first inorganic particles having a first average energy bandgap, and a plurality of second inorganic particles having a second average energy bandgap smaller than the first average energy bandgap

Methodology Applied

Scientific EffectElectron transport: Conduction (electrical)

Implementation Method 2

when electric charges are injected into an organic emissive layer formed between an electron injection electrode (cathode) and a hole injection electrode (anode), electrons and holes are paired and recombined to emit light

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS10665805B2Light-emitting diode and light-emitting device including the same

Publication Date: 2020.05.26 LG DISPLAY CO LTD

AI summary

A light emitting diode includes a first electrode and a second electrode facing the first electrode. The light emitting diode further includes an emitting material layer (EML) disposed between the first electrode and the second electrode, and an electron transport layer (ETL) adjacent the EML. The ETL includes a plurality of first inorganic particles having a first average particle size, and a plurality of second inorganic particles having a second average particle size greater than the first average particle size. The plurality of first inorganic particles may also have a first energy bandgap, and a plurality of second inorganic particles may also have a second energy bandgap smaller than the first energy bandgap.