KR-102963219-B1 - Method for manufacturing quantum dot ink using non-toxic colloidal quantum dots and optoelectronic devices manufactured thereby

Abstract

Infrared (IR) optoelectronics is becoming increasingly important due to various applications such as perception, autonomous driving, and quantum communication. In particular, detection and emission at a wavelength of 1550 nm in the shortwave IR (SWIR) spectrum have been studied with eye safety, long-distance communication, and efficient perception in mind. Recently, III-V colloidal quantum dots (CQDs) have attracted significant attention due to their optical bandgap tunability, non-toxicity, and lower cost compared to epitaxially grown semiconductors. However, most research on CQD photodetectors operating at 1550 nm has been conducted using toxic materials such as Pb and Hg. In this invention, we propose a non-toxic III-V CQD-based SWIR optoelectronic device using a novel synthesis approach.

Inventors

• 백세웅
• 시민재
• 지승인

Assignees

• 고려대학교 산학협력단

Dates

Publication Date

20260508

Application Date

20231130

Claims (20)

1. A first step of synthesizing first and second quantum dots, respectively, composed of non-toxic Group III-V materials capped with oleic acid (OA) ligands on their surfaces; A second step of preparing first and second quantum dot solutions by dispersing the synthesized first and second quantum dots in a first solvent, respectively, and preparing first and second ligand solutions by dispersing the first and second ligands in a second solvent, respectively; and The method comprises a third step of reacting the first quantum dot solution with the first or second ligand solution and reacting the second quantum dot solution with the first or second ligand solution to produce a first quantum dot ink comprising a first quantum dot exchanged with a first or second ligand and a second quantum dot ink comprising a second quantum dot exchanged with a first or second ligand. The first quantum dot has n-type semiconductor characteristics as InAs, and the second quantum dot has p-type semiconductor characteristics as InSb, and A method for manufacturing a quantum dot ink characterized in that the first ligand is a thiol ligand and the second ligand is a halide ligand.
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5. In paragraph 1, A method for manufacturing a quantum dot ink characterized in that the diameter of the first and second quantum dots is 5 to 6 nm.
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7. In paragraph 1, The above thiol ligand includes mercaptopropionic acid (3-mercaptopropionic acid), and A method for manufacturing a quantum dot ink characterized by the above halide ligand comprising at least one selected from InBr3 , InI3 , and InCl3 .
8. In paragraph 1, The first solvent above includes dimethylformamide (DMF), and A method for manufacturing quantum dot ink characterized in that the second solvent comprises octane.
9. In paragraph 1, In the third step above, The first quantum dot solution reacts with the first or second ligand solution, wherein the volume ratio of the first or second ligand solution to the first quantum dot is 1:1 to 2, and A method for manufacturing a quantum dot ink, characterized in that the second quantum dot solution reacts with the first or second ligand solution, wherein the volume ratio of the first or second ligand solution to the second quantum dot is 1:1 to 2.
10. In Paragraph 9, When the above-mentioned second quantum dot and second ligand solution react, A method for manufacturing quantum dot ink characterized by adding a basic substance together with the above-mentioned second ligand and then reacting by vigorously stirring.
11. In Paragraph 9, A method for manufacturing quantum dot ink, characterized by adding a basic substance together with the second ligand and reacting by vigorously stirring, wherein 0.1 M of the second ligand and 0.045 M of the basic substance are added and reacted by vigorously stirring.
12. In Paragraph 11, A method for manufacturing a quantum dot ink characterized by the above basic material comprising at least one selected from ammonium acetate, methylammonium acetate, and sodium acetate.
13. In paragraph 1, A method for manufacturing quantum dot ink characterized by further including a process of purifying the first and second quantum dot solutions using a third solvent.
14. In Paragraph 13, The third solvent is injected into the first or second quantum dot solution in a volume ratio of 1:2 to 3, and A method for manufacturing quantum dot ink characterized by removing reaction residues by centrifuging at 2000 to 4000 rpm for 1 to 10 minutes.
15. In Paragraph 14, A method for manufacturing quantum dot ink characterized in that the third solvent comprises toluene or hexane.
16. A photoelectronic device comprising: a substrate; a transparent electrode layer formed on the substrate; an electron transport layer stacked on the transparent electrode layer; a quantum dot photoactive layer stacked on the electron transport layer; a hole transport layer stacked on the quantum dot photoactive layer; and an electrode layer stacked on the hole transport layer. The optoelectronic device characterized in that the above quantum dot photoactive layer is formed using a first quantum dot ink and a second quantum dot ink prepared according to any one of claims 1, 5, 7 to 15.
17. In Paragraph 16, The above quantum dot photoactive layer is formed by applying a mixed ink in which the first quantum dot ink and the second quantum dot ink are mixed, and An optoelectronic device characterized by the above-described mixed ink being formed in a volume ratio of the second quantum dot ink to the first quantum dot ink of 1:1 to 2.
18. In Paragraph 16, The first quantum dot ink comprises a first quantum dot exchanged with a first or second ligand, and the second quantum dot ink comprises a second quantum dot exchanged with a first or second ligand. An optoelectronic device characterized in that the first quantum dot has n-type semiconductor characteristics and the second quantum dot has p-type semiconductor characteristics.
19. In Paragraph 18, The optoelectronic device characterized in that the first and second quantum dots are made of a non-toxic Group III-V material.
20. In Paragraph 19, A photoelectronic device characterized in that the above-mentioned non-toxic Group III-V material is a binary compound based on indium (In) containing one of phosphorus (P), arsenic (As), or antimony (Sb).

Description

Method for manufacturing quantum dot ink using non-toxic colloidal quantum dots and optoelectronic devices manufactured thereby The present invention relates to a method for manufacturing quantum dot ink using non-toxic colloidal quantum dots and an optoelectronic device manufactured thereby. Colloidal quantum dots (CQDs) are promising semiconductor materials for the development of next-generation infrared optoelectronics used in autonomous driving, virtual reality, perception, and quantum technology. In particular, due to their unique physical properties and quantum confinement effects, CQDs offer a broad absorption spectrum spanning from visible light to the mid-infrared region compared to other novel solution-processed semiconductors such as perovskites and organic molecules. To date, CQDs of the II-VI and IV-VI groups (e.g., HgTe, PbSe, PbS) have been widely studied for applications in the optoelectronics field, but their commercial viability is limited due to the use of toxic elements such as Cd, Pb, and Hg. Recently, III-V CQDs (e.g., InAs and InSb) have garnered significant attention as IR materials due to their narrow bulk bandgap and compliance with the Restriction of Hazardous Substances (RoHS) directive. Although several studies have evaluated InAs CQD-based IR photodetectors, the efficiency of these devices was significantly lower compared to PbS-based devices. Furthermore, while current state-of-the-art methods demonstrate the photoresponse of photodetectors only up to the near-IR (NIR) region (<1100 nm), it is crucial to extend the absorbance to the short-wavelength infrared region above 1550 nm for eye safety and efficient distance measurement and recognition. One of the major challenges for III-V CQDs is controlling monodispersity and surface passivation. The synthesis of III-V CQDs (e.g., InAs and InSb) is difficult to overcome because the high reactivity of precursors induces unwanted secondary nucleation, resulting in low chemical reaction yields and poor uniformity. Furthermore, surface ligand exchange in InSb CQDs is difficult due to the high covalent nature of the lattice and high formation energy. To address these issues, key strategies must be developed to fabricate high-performance optoelectronic materials, ranging from the synthesis stage to surface passivation. FIG. 1 is a drawing for explaining a method for manufacturing quantum dot ink according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing the energy levels of a quantum dot ink manufactured according to one embodiment of the present invention. FIG. 3 is a diagram illustrating the structure of a photoelectronic device according to one embodiment of the present invention. FIG. 4 is a schematic diagram showing an energy level diagram in a photoactive layer according to one embodiment of the present invention. Figure 5 is a diagram illustrating the synthesis method of IR InSb CQD. Figure 6 is a diagram illustrating the surface reconstruction of InSb CQD. Figure 7 is a diagram showing the physical properties of InSb CQD solids. Figure 8 is a diagram illustrating an IR InSb CQD-based BHJ (bulk heterojunction) photodiode. Figure 9 is a diagram showing the absorption spectra of InSb nanoclusters at various cluster concentrations, 226.6 mM (green) and 348.8 mM (yellowish-brown). Figure 10 shows the absorption spectra of InSb CQD before (green) and after (yellowish-brown) removal of insoluble byproducts for the size selection process. Figure 11 is a diagram showing the comparison results of InSb CQD shapes according to various cluster concentrations. Figure 12 shows a tauc plot of the InSb CQD absorption spectrum for determining the band gap energy (Eg), and the optical band gap of InSb CQD was calculated by extrapolating the linear part of the spectrum. Figure 13 is a diagram showing the results of a comparison between the theoretical trend (yellow dashed line) based on the eight-band effective mass approximation proposed by Efros and Rosen and our experimental data (brown, solid line). Figure 14 is a diagram showing the comparison results of the InSb CQD form using TEM. Figure 15 is a diagram showing the UPS spectra of InAs-MPA (green) and InAs-InBr3 (yellowish-brown) CQD solid films. Figure 16 is a diagram showing the KPFM potential image and distribution of an InSb CQD film. Figure 17 is a figure showing the normalized absorption spectrum of an InSb CQD solid containing OA (brown), MPA (yellowish-brown), and InBr 3 (green) ligands. Figure 18 is a diagram showing the absorbance of InAs CQD used to fabricate a III-V CQD bulk heterojunction (BHJ) photodiode. Figure 19 is a diagram showing the transient photoresponse under NIR (940 nm) and SWIR (1,550 nm) illumination. Figure 20 is a diagram of the thickness of the InSb:InAs CQD BHJ thin film using the Dektak-XT surface profiler, and the thickness values were used to analyze the SCLC measurements. Hereinafter, preferred embodiments of the present inven