Quantum Dot LED Layer Stack Using Resonant Energy Transfer

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

InP-based quantum dot light emitting diodes (QD-LEDs) exhibit low external quantum efficiencies due to quenching in close-packed films, leading to high operating voltages and poor power efficiency, while increasing shell thickness to enhance quantum yield also increases charge injection barriers.

Innovation Solution

The use of a layer stack with luminescent nanostructures, such as quantum dots, where the electron transport layer and hole transport layer contact each other through discontinuities, allowing for resonant energy transfer from excitons in the electron transport layer to the quantum dots, reducing the need for direct carrier injection and enabling higher shell thickness without increasing turn-on voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If shell thickness around quantum dot core material is increased to counteract low quantum yield, then quantum yield is improved, but charge injection barrier increases requiring higher operating voltages

Engineering Contradiction:

Improvequantum yieldVSAvoidoperating voltage

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent introduces an electron transport layer as an intermediary between the cathode and quantum dots. This layer mediates charge injection by providing a favorable energy level alignment that facilitates electron injection without requiring high operating voltages, thus resolving the contradiction between achieving high quantum yield through thick shells and maintaining low operating voltages.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If InP quantum dots are deposited into close-packed films, then device structure is simplified, but quenching occurs reducing external quantum efficiency

Engineering Contradiction:

Improvefilm structureVSAvoidexternal quantum efficiency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent applies local quality by creating a discontinuous quantum dot layer with isolated dots rather than close-packed films. This local arrangement prevents quenching interactions while maintaining structural simplicity, resolving the contradiction between simplified device structure and high external quantum efficiency.

Inventive Principle:

Principle #3Local quality

3Device complexity

If direct carrier injection is used to stimulate quantum dots, then device structure is simple, but high operating voltages are required resulting in poor power efficiency

Engineering Contradiction:

Improvedevice structureVSAvoidpower efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent replaces direct electrical carrier injection (mechanical/electrical system) with optical excitation through an electron transport layer that transfers excitons to quantum dots. This substitution enables efficient energy transfer at low operating voltages, resolving the contradiction between simple device structure and high power efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 results in QD-LEDs with improved quantum yield and low operating voltages, achieving external quantum efficiencies up to 12.3% and a turn-on voltage of about 1.5 V, while maintaining device stability and efficiency.

Implementation Method 1

allowing for resonant energy transfer from excitons in the electron transport layer to the quantum dots

Methodology Applied

Scientific EffectResonant energy transfer:

Implementation Method 2

stimulating the energy states of the quantum dots

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS12010860B2Quantum dot LED design based on resonant energy transfer

Publication Date: 2024.06.11 SHOEI CHEM IND CO LTD

AI summary

Embodiments of the present application relate to illumination devices using luminescent nanostructures. An illumination device includes a first conductive layer, a second conductive layer, a hole transport layer, an electron transport layer and a material layer that includes a plurality of luminescent nanostructures. The hole transport layer and the electron transport layer are each disposed between the first conductive layer and the second conductive layer. The material layer is disposed between the hole transport layer and the electron transport layer and includes one or more discontinuities in its thickness such that the hole transport layer and the electron transport layer contact each other at the one or more discontinuities. Resonant energy transfer occurs between the luminescent nanostructures and excitons at the discontinuities.