2021 Fiscal Year Research-status Report
High Performance Supercapacitors based on Hierarchical Colloidal Quantum Dot Assemblies
| Project/Area Number |
21K04815
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
Bisri Satria 国立研究開発法人理化学研究所, 創発物性科学研究センター, 研究員 (70748904)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | colloidal quantum dots / nanocrystals / supercapacitors / electric-double-layer / electrochemical devices / energy storage / quantum capacitance |
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| Outline of Annual Research Achievements |
This project aims to study the physical properties and develop high-performance supercapacitor devices based on assemblies of colloidal quantum dots (QD). In FY2021, we specifically focused the research on several basic understanding related to the QD assemblies, charge accumulation and prediction of properties that may arise from several material options. We developed assembly methods of QDs to become square superlattice for carrier transport, and hierarchical porous assemblies for supercapacitor. We investigated charge accumulation in QD by combination of transistor and spectroelectrochemistry measurements. We are able to confirmed the band filling of the QD by observing both the negative transconductance and the bleaching of the QD excitonic peak while doped via electric-double-layer formation. We also successfully synthesized pi-SnS QDs, the first of its kind. The pi-SnS phase is a low-symmetry cubic structure. Normally, SnS has orthrombic structure. Therefore, some new properties are expected. For the first, time SnS QD can be synthesized close to its Bohr radius and quantum confinement effect can be observed. On the other hand, we also predicted the properties of h-FeS NCs, as another environmentally-benign materials prospective to replace PbS QDs in the assemblies.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The research project is running as planned, with some fronts progressing faster than expected. Nowadays, we can perform precise facet control of the QDs, and it has an important consequence in tuning the inter-QD distance and the orientation homogeneity of the QD assemblies. We performed some thorough structural investigation by conducting GISAXS/GIWAXS measurements at SPring-8 Synchrotron Radiation Facilities.
Also, through layer-by-layer dip-coating, we precisely tuned the formation of the hierarchical porous assembly of the QDs and modify their surface properties, enhancing the conductivity. The current supercapacitor measurement also showed promising results that will be further advanced in the next FY.
From the material development front, the synthesized SnS QD has unique crystal structure, distinct from the other known crystalline phases. Some emerging properties stem from the new crystalline phase are highly expected.
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| Strategy for Future Research Activity |
In the next fiscal year, the project's focus will be sharpened on the direction of the supercapacitor measurements, in which variations of ionic liquids and ion gels will be used against the PbS QD assembly electrodes. So far, we are still utilizing EMIM-TFSI ionic liquid. Ionic liquids with wider electrochemical window, more capacitive, and possessing surface-active ionic liquid characteristics will be used. In addition to performing supercapacitor measurement via three-electrode characterization, we are going to further develop the microsupercapacitor architecture to show the real potential of this solution processable materials. On the other hand, hierarchical assemblies developments will start focusing on the utilization of both the newly synthesized pi-SnS QD and the Fe-X NCs.
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| Causes of Carryover |
Some small amount (less than 500 yen) remains due to non-round prices of articles that were purchased. Meanwhile, this value is too small to be spent for meaningful small article. Therefore, it will be used with the budget in the next fiscal year to purchase the planned research equipment or consumables. We are anticipating to purchase a battery analyzer to support the research project.
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