Quantum Dot Emission Layer Ligand Removal for Density
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Solution Overview
Problem
Current light emitting elements using quantum dots face challenges in enhancing luminous efficiency and service life due to limitations in the dispersibility and capping properties of ligands, which inhibit charge injection and result in reduced quantum dot stacking density.
Innovation Solution
A method for manufacturing a light emitting element involves forming an emission layer by removing a part or all of the ligands bonded to the surface of quantum dots, increasing the layer density by 5% or greater, using a quantum dot composition with a ligand that includes a radical reactive group or a polar solvent dissociative functional group, and applying heat or light to induce ligand removal, thereby improving quantum dot dispersion and charge injection properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If ligands are used to cap quantum dot surfaces, then quantum dot stability and dispersibility are improved, but charge injection properties and quantum dot stacking density are inhibited
Solution Approach 1:
The patent removes ligands from the quantum dot surface after the quantum dots are formed and dispersed. This extraction process eliminates the harmful ligand layer that blocks charge injection, while the quantum dots maintain their stability and dispersibility that were established during formation with ligands present
Solution Approach 2:
The patent applies ligands to quantum dots in advance during the quantum dot formation and deposition process to ensure proper dispersibility and stability. Then, in a subsequent step, the ligands are removed to enable charge injection. This preliminary application followed by removal resolves the contradiction between needing ligands for stability and needing their absence for charge injection
2Stability of the object's composition
If ligands are used to disperse quantum dots, then quantum dot dispersibility is improved, but quantum dot stacking density is reduced
Solution Approach 1:
The patent removes ligands from the quantum dot surface to eliminate the spacing effect that ligands create between quantum dots. By extracting the ligand layer, quantum dots can stack more densely while maintaining their dispersibility characteristics that were established during the deposition process
Solution Approach 2:
The patent changes the physical and chemical parameters of the quantum dot surface by removing ligands. This parameter change (from ligand-capped to ligand-free surface) enables increased quantum dot stacking density while preserving the dispersibility that was achieved during the deposition process
3Reliability
If ligands are removed from quantum dot surface, then charge injection properties and quantum dot stacking density are improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines the ligand removal step with existing manufacturing processes such as thermal annealing or solvent treatment that are already used for other purposes in light emitting element fabrication. By merging the ligand removal function with existing process steps, the manufacturing complexity is minimized while still achieving the desired charge injection properties and quantum dot stacking density
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
The method results in a light emitting element with improved luminous efficiency and service life by increasing quantum dot stacking density, preventing degradation of charge injection properties, and enhancing the dispersion of quantum dots in the emission layer.
Implementation Method 1
The increasing of the layer density of the preliminary emission layer may be performed by providing heat and/or light to the preliminary emission layer
Implementation Method 2
applying heat or light to induce ligand removal
Implementation Method 3
preparing the quantum dot composition by dispersing the quantum dot and the ligand bonded to the surface of the quantum dot in an organic solvent
Data Source
AI summary
A method for manufacturing a light emitting element includes: forming a first electrode; forming a hole transport region on a first electrode; forming an emission layer on the hole transport region; forming an electron transport region on the emission layer; and forming a second electrode on the electron transport region, wherein the forming of the emission layer includes providing a quantum dot composition containing a quantum dot and a ligand bonded to a surface of the quantum dot, to form a preliminary emission layer; and increasing the layer density of the preliminary emission layer by about 5% or greater, thereby improving a luminous efficiency of the light emitting element.