Low-pKa Quantum Dot Dispersion Liquid for Infrared Detection
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Solution Overview
Problem
Existing quantum dot dispersion liquids for photodetectors have low dispersibility and external quantum efficiency, requiring time-consuming ligand exchange treatments, which increase costs and hinder high sensitivity to infrared light.
Innovation Solution
A dispersion liquid containing quantum dots with a band gap of 1.35 eV or less, using a ligand with a pKa of 3 or less, and a solvent, allowing for improved dispersibility and external quantum efficiency without additional ligand exchange steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a ligand with a long molecular chain length (e.g., oleic acid) is used to improve dispersibility of quantum dots, then dispersibility is improved, but the distance between quantum dots becomes long and external quantum efficiency decreases
Solution Approach 1:
The patent changes the key parameter of the ligand from long molecular chain length to low pKa value (3 or less). This parameter change allows the ligand to provide sufficient dispersibility while maintaining short distance between quantum dots, thereby achieving high external quantum efficiency without requiring ligand exchange treatment.
2Reliability
If ligand exchange treatment is performed to achieve high external quantum efficiency, then external quantum efficiency is improved, but the process becomes time-consuming and costly
Solution Approach 1:
The patent applies preliminary action by pre-selecting ligands with low pKa values (3 or less) before quantum dot film formation. This preliminary selection ensures that the quantum dots maintain both good dispersibility and high external quantum efficiency directly after film formation, eliminating the need for subsequent ligand exchange treatment and reducing process time.
Solution Approach 2:
The patent extracts the ligand exchange treatment step from the manufacturing process by using ligands with low pKa values that inherently provide both dispersibility and high external quantum efficiency. This extraction eliminates the time-consuming and costly ligand exchange step while maintaining the desired performance.
3Stability of the object's composition
If conventional quantum dot dispersion liquids are used, then quantum dots can be dispersed, but additional ligand exchange steps are required which increase manufacturing complexity
Solution Approach 1:
The patent applies universality by using ligands with low pKa values (3 or less) that simultaneously provide multiple functions: ensuring good dispersibility of quantum dots and maintaining high external quantum efficiency. This multi-functionality eliminates the need for separate ligand exchange steps, thereby simplifying the manufacturing process.
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 solution enables the formation of a quantum dot film with enhanced dispersibility and high external quantum efficiency, particularly sensitive to infrared light, suitable for photodetectors and image sensors.
Implementation Method 1
the ligand contains a compound having a pKa of 3 or less or a salt of the compound
Data Source
AI summary
A dispersion liquid including quantum dots having a band gap of 1.35 eV or less; a ligand; and a solvent, in which 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, and the ligand contains a compound having a pKa of 3 or less or a salt of the compound. A photoelectric conversion film using a dispersion liquid, a method for manufacturing a photoelectric conversion film, a photodetector, and an image sensor.