Quantum Dot Ligands with Conjugated Bridges for Charge Transfer

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Solution Overview

Problem

In optoelectronic semiconductor components, especially those using cadmium-free quantum materials, there is a challenge with poor light emission due to insufficient charge transfer and recombination of charge carriers, primarily because traditional ligand shells with long-chain hydrocarbon chains hinder electrical excitation, and existing approaches to enhance charge transfer have not shown significant improvement.

Innovation Solution

A quantum material is developed with a quantum dot having ligands that include a first functional group and a second functional group bound by a bridge comprising a system of conjugated double bonds, which facilitates improved charge transfer by acting as an 'antenna' and 'bridge' for charge carriers, enhancing the transport of positive and negative charges to the quantum dot.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If traditional ligand shells with long-chain hydrocarbon chains are used, then the quantum materials can be stably suspended in liquid, but charge transfer to the quantum material is suppressed and electrical excitation is hindered

Engineering Contradiction:

Improvestability of quantum material suspensionVSAvoidcharge transfer efficiency

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The ligand shell is designed with spatially differentiated functionality: the first functional group (e.g., carboxylate, thiolate) provides stable binding to the quantum dot surface, while the second functional group (e.g., amino, hydroxyl) provides charge transfer capability. This local differentiation allows simultaneous achievement of stability and charge transfer efficiency.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The ligand is designed as a composite molecular structure combining multiple functional groups with different properties. The ligand integrates surface-binding functionality (from carboxylate/thiolate groups) and charge-transport functionality (from amino/hydroxyl groups) into a single molecular entity, creating a composite ligand that performs multiple functions simultaneously.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If vapor deposition is used to create layer stack, then component architecture can be formed, but inorganic quantum materials decompose or require temperatures that compromise component integrity

Engineering Contradiction:

Improvelayer stack formationVSAvoidcomponent integrity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent replaces thermal processing (vapor deposition) with liquid processing methods. The quantum materials are processed in liquid form using techniques such as spin coating, doctor blade coating, or inkjet printing, allowing deposition at lower temperatures that preserve component integrity while still enabling formation of functional layer stacks.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If saturated long-chain hydrocarbon chain ligands are used, then quantum materials can be dispersed in solvent, but charge transfer support is limited and electrical excitation is suppressed

Engineering Contradiction:

Improvedispersion capabilityVSAvoidelectrical excitation efficiency

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The ligand molecular structure is modified by changing chemical parameters - specifically replacing saturated hydrocarbon chains with functional groups containing unsaturated bonds and heteroatoms. This parameter change transforms the ligand from a purely dispersive function to one that also supports charge transfer through conjugated pi-electron systems and lone pair electrons.

Inventive Principle:

Principle #35Parameter changes

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 significantly improves the efficiency of charge carrier transport and recombination, leading to enhanced light emission in optoelectronic semiconductor components, such as OLEDs and QLEDs, by facilitating balanced charge transfer and reducing degradation from excess charge carriers.

Implementation Method 1

the bridge comprises a system of conjugated double bonds, which facilitates improved charge transfer by acting as an 'antenna' and 'bridge' for charge carriers, enhancing the transport of positive and negative charges to the quantum dot

Methodology Applied

Scientific EffectCharge transfer: Conduction (electrical)

Data Source

PatentUS12152181B2Quantum materials having improved charge transfer for use in optoelectronic semiconductor components

Publication Date: 2024.11.26 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

A quantum dot material may include a quantum dot having at least two ligand where each ligand includes a first and a second functional group bound to each other by a bridge. The bridge may include a system of conjugated double bonds. In at least one ligand, the second functional group may have an electron transport structure. In at least one ligand, the second functional group may have a hole transport structure.