Electroluminescent Device Dual Light Emitting Layer Charge Balance

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Solution Overview

Problem

Quantum dot electroluminescent devices face challenges with exciton quenching due to uneven charge flow and recombination at interfaces, leading to reduced luminous efficiency and lifespan, as excitons are often trapped and quenched at the interface between the hole transport layer and the light emitting layer.

Innovation Solution

Incorporating a dual light emitting layer structure with an n-type metal oxide in the second light emitting layer to achieve a stable hole-electron balance, adjusting the recombination position of electrons and holes from the interface to inside the light emitting layer, and using a p-type semiconductor in the first light emitting layer to enhance charge balance and efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single light emitting layer with quantum dots is used, then the device structure is simple, but exciton quenching occurs at the interface between the hole transport layer and the light emitting layer, reducing luminous efficiency

Engineering Contradiction:

Improvelight emitting layer structureVSAvoidluminous efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The single light emitting layer is divided into two sub-layers: a first light emitting layer containing quantum dots and a second light emitting layer containing n-type metal oxide nanoparticles. This segmentation allows the first layer to generate excitons while the second layer facilitates electron-hole recombination, preventing exciton quenching at the interface and improving luminous efficiency without significantly increasing overall device complexity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The n-type metal oxide nanoparticles in the second light emitting layer act as an intermediary that promotes electron-hole recombination. These nanoparticles serve as recombination centers that capture electrons and holes, enabling efficient radiative recombination and preventing exciton quenching that would otherwise occur at the hole transport layer interface

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If the light emitting layer thickness is increased to improve quantum efficiency, then more quantum dots are available for light emission, but exciton quenching increases due to larger interface area

Engineering Contradiction:

Improvequantum efficiencyVSAvoidexciton quenching

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The light emitting layer is designed with different local properties in different regions: the first light emitting layer contains quantum dots optimized for light emission, while the second light emitting layer contains n-type metal oxide nanoparticles optimized for electron-hole recombination. This local quality differentiation allows each region to perform its specific function efficiently, improving overall quantum efficiency while minimizing exciton quenching through the recombination-active second layer

Inventive Principle:

Principle #3Local quality

3Loss of energy

If charge balance is improved by adding more electron transport materials, then electron-hole recombination is enhanced, but the device structure becomes more complex

Engineering Contradiction:

Improvecharge balanceVSAvoidlight emitting layer structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent combines light emission functionality and electron-hole recombination functionality into a single integrated light emitting layer structure. The second light emitting layer with n-type metal oxide nanoparticles serves dual purposes: maintaining charge balance through enhanced recombination and preventing exciton quenching, thereby improving charge balance without requiring separate electron transport layers or additional complex structures

Inventive Principle:

Principle #5Merging (Combining)

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 improves luminous efficiency and lifespan by ensuring efficient electron-hole recombination within the light emitting layer, reducing exciton quenching and enhancing the electroluminescent device's performance.

Implementation Method 1

A quantum dot ('QD') is a nanocrystal of semiconductor material with a diameter of about several nanometers to several tens of nanometers, which exhibits a quantum confinement effect. The quantum dot generates stronger light in a narrow wavelength region than commonly used phosphors. The quantum dot emits light while the excited electrons are transited from a conduction band to a valence band

Methodology Applied

Scientific EffectQuantum confinement effect:

Implementation Method 2

The quantum dot emits light while the excited electrons are transited from a conduction band to a valence band

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS11476434B2Electroluminescent device and display device comprising thereof

Publication Date: 2022.10.18 SAMSUNG ELECTRONICS CO LTD

AI summary

An electroluminescent device includes a first electrode and a second electrode facing each other, and a light emitting layer disposed between the first electrode and the second electrode, where the light emitting layer includes a first light emitting layer including a first quantum dot and a second light emitting layer including a second quantum dot and an n-type metal oxide.