All-Inorganic Quantum Dot Layers for Charge Transport

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current quantum dot/polymer solar cells and optoelectronic devices face efficiency losses due to charge carrier recombination at the organic/inorganic interface and inefficient charge transport, primarily because of the insulating organic surfactant layers and the tunneling process.

Innovation Solution

The development of all-inorganic nanostructured layers composed of three or more colloidal quantum dot populations, where each population can be in electrical contact to form electron or hole transport conduits, eliminating the need for organic materials and enhancing charge transport and recombination efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If organic surfactant layers are used to enable quantum dot dispersion and deposition, then ease of manufacture is improved, but charge carrier mobility and electrical conductivity deteriorate due to insulating properties

Engineering Contradiction:

Improveease of depositionVSAvoidcharge transport efficiency

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent removes organic surfactant layers from the quantum dot structure and replaces them with inorganic ligands. This extraction of the harmful organic component eliminates the insulating barrier while maintaining the quantum dots' dispersibility and film-forming capabilities through inorganic coordination chemistry.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the chemical nature of the ligand shell from organic to inorganic, fundamentally altering the electrical properties of the quantum dot surface. This parameter change transforms the material from electrically insulating to electrically conductive, enabling efficient charge transport while preserving ease of manufacture through solution processing.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If quantum dots are dispersed in polymer matrices, then ease of manufacture is improved, but charge carrier recombination losses increase due to organic/inorganic interface states

Engineering Contradiction:

Improveease of fabricationVSAvoidcharge carrier recombination loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent extracts quantum dots from organic polymer matrices and creates all-inorganic nanostructured layers. This removal of the organic polymer environment eliminates the source of interfacial recombination states while maintaining fabrication simplicity through direct inorganic ligand exchange and annealing processes.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent creates a composite inorganic structure where quantum dots are coupled through inorganic ligands, forming an all-inorganic composite material. This composite approach combines the advantages of quantum dot size-tunability with efficient charge transport, eliminating organic/inorganic interface losses while maintaining ease of fabrication.

Inventive Principle:

Principle #40Composite materials

3Device complexity

If tunneling processes are used for charge transfer across organic layers, then device simplicity is maintained, but charge transport efficiency deteriorates

Engineering Contradiction:

Improvestructural simplicityVSAvoidcharge transport efficiency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent replaces the quantum mechanical tunneling mechanism (which operates through insulating organic barriers) with direct inorganic band-to-band charge transfer. This substitution eliminates the exponential distance dependence of tunneling and enables efficient charge transport through delocalized inorganic ligand states while maintaining structural simplicity.

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 increases charge carrier mobilities and reduces nonradiative recombination losses, leading to improved solar conversion efficiencies and broader light absorption/emission capabilities in optoelectronic devices.

Implementation Method 1

Multiple exciton generation (MEG) in lead sulfide quantum dots supplied by Evident Technologies can create more than one electron hole pair per absorbed photon provided that the photon energy is more than twice that of the quantum dot bandgap

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Implementation Method 2

Methodology Applied

Scientific EffectMultiple exciton generation:

Implementation Method 3

Semiconductor quantum dot (QD) based solar cells are ideally suited to increase conversion efficiencies because they have size and compositionally tunable bandgaps and broadband absorption

Methodology Applied

Scientific EffectQuantum confinement effect:

Data Source

PatentUS8368048B2Nanostructured layers, methods of making nanostructured layers, and application thereof

Publication Date: 2013.02.05 NANOCO TECH LTD

AI summary

One embodiment of the invention provides a nanostructure layer, comprising: a first population of semiconductor nanocrystals forming electron transport conduits; a second population of semiconductor nanocrystals forming hole transport conduits; and a third population of semiconductor nanocrystals capable of at least one of the following: absorbing light or emitting light.