Quantum Dot Dispersion Composition for Uniform Infrared Films
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Solution Overview
Problem
Existing dispersion liquids for quantum dots suffer from low dispersibility and thickness unevenness, leading to reduced optical response and performance variability in quantum dot films, particularly in the infrared region.
Innovation Solution
A dispersion liquid comprising quantum dots, a ligand, and a solvent containing specific compounds or polycyclic ketones, with a high quantum dot content, which enhances dispersibility and reduces thickness unevenness, allowing for high-density film formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ligand having a long molecular chain length is used in the dispersion liquid, then the dispersibility of quantum dots is improved, but the distance between quantum dots becomes long and external quantum efficiency becomes low
Solution Approach 1:
The patent changes the molecular chain length parameter of the ligand from long (e.g., oleic acid) to short (e.g., mercaptopropionic acid with 3 carbon atoms). This parameter change reduces the distance between quantum dots in the film, improving optical response and external quantum efficiency while maintaining adequate dispersibility through the high quantum dot content (50% by mass or more).
Solution Approach 2:
The patent performs preliminary action by forming a quantum dot film directly using a dispersion liquid with short-chain ligands and high quantum dot content, eliminating the need for subsequent ligand exchange processes. This preliminary formulation approach achieves both good dispersibility and high external quantum efficiency in a single step.
2Productivity
If a ligand having a short molecular chain length is used in the dispersion liquid, then the external quantum efficiency is improved, but the dispersibility of quantum dots tends to reduce
Solution Approach 1:
The patent optimizes the quantum dot content parameter to 50% by mass or more, which compensates for the reduced dispersibility caused by short-chain ligands. This high concentration ensures adequate quantum dot spacing and film uniformity while maintaining the benefits of short ligand chains for high external quantum efficiency.
3Ease of manufacture
If the dispersion liquid has thickness unevenness, then the manufacturing process is simple, but the absorbance of the film changes and performance becomes uneven
Solution Approach 1:
The patent changes the viscosity parameter of the dispersion liquid by selecting specific solvents (nitriles, esters, ethers, amides, or their mixtures) to achieve optimal flow characteristics. This viscosity optimization ensures uniform film thickness during the coating process while maintaining simple manufacturing procedures.
Data Source
AI summary
There is provided a dispersion liquid including quantum dots, a ligand, and a solvent, in which the solvent includes at least one selected from a compound represented by Formula (1) or a polycyclic ketone compound, and a content of the quantum dots in a component obtained by removing the solvent and the ligand from the dispersion liquid is 50% by mass or more. There are also provided methods for manufacturing a quantum dot film using the dispersion liquid described above, a photodetector, and an image sensor.