Research Contents
New correlation between heat and electrons
Now I am working on two big topics: Thermal Energy conversion, and Plasmonic nanostructures.
Semidonductor-Sensitized Thermal Cell
Semiconductor-sensitized thermal cells (STCs) is a new green power generation system operate by heating without a cooling temperature part. The structure of STC imitates the dye-sensitized solar cells (DSSCs).
In DSSCs, electrons in dyes are photoexcited by light irradiation, and the excited electrons are injected into the conduction band of an electron transport material. The transported electrons reduced oxidant ions in electrolyte, and the reductant ions were oxidized by the photoexcited holes, and we can get photo-excited current.
If thermally excited electrons in the semiconductor can generate the ion redox reactions, a novel heat-to-electron conversion system functioned without a temperature difference, named a “sensitized thermal cell”, can be obtained (Japanese Patent Application No. 2015-175037).
The first step was to confirm whether the thermally excited charges could cause the redox reaction of ions (Mater. Horiz., 2017, 4, 649–656). As a result, long-term power generation at 600 ° C was confirmed using β-FeSi2 and a copper ion conductor.
However, at this time, in order to confirm the redox reaction of the ions, the electrolyte with very low ion mobility was used.
Therefore, in order to confirm the principle, we focused on organic perovskite sensitized solar cells, which use semiconductors as the sensitiser. This organic perovskite is famous as a solar cell material, and it has been shown by calculation that it is possible to generate electrons by heat. If this organic perovskite-type sensitized cell can generate electricity with light or heat, it is a clear proof of the principle of sensitized thermal power generation. The experiment became difficult due to the fragility of the organic perovskite, but finally it was possible to confirm the power generation with light or heat (ACS Appl. Energy Mater., 2019, 2, 13–18) .
The next question was, "Does this battery stop generating power?" This question was the ultimate in this battery compared to a permanent engine immediately after proposed. To confirm the end of power generation, we used a polymer electrolyte that can adjust the amount of electrolyte ions and has relatively high durability. Even more surprisingly, it has been confirmed that the ability to generate electricity is restored by utilizing the diffusion of ions in the electrolyte by thermal energy. In other words, the battery can revert this situation itself in the presence of heat by simply opening the external circuit for some time; in other words, by using a simple switch. (J. Mater. Chem. A, 2019, 2019,7, 18249-18256).
In 2021, we found that this restore phenomena has a big relationship with the electrode thickness (https://www.researchsquare.com/article/rs-384614/v7). This finding enables us to generate electric power at room temparature.
If you are interested in this battery and are experimenting, please be aware of the following two points:
1) Even if power generation can be confirmed by I-V, make sure that the electrode materials are not solved.
2) Take chrono potentiometry. Even with a simple capacitor, the open-circuit voltage can be confirmed by I-V, so take time dependency of the voltage during discharge and make sure that the plateau region is released. At this time, make the discharge current smaller.
The video below is used at the press release on July 18, 2019. By connecting four lab level batteries in series and warming to 90 ° C, the liquid crystal display lights up.
Frequently asked questions are summarized in this page .
Sorry in Japanese.
Plasmonic Nanostructures
Plasmon has various interesting properties, especially combined with direlectric materials. We fabricated a wide range of plasmonic nanostructures such as metal-dielectric-metal (MIM) structures in a simple method. Currently, our works are expanded to:
- Beautiful coloring materials
- Flow control in microchannel
- Chemical reaction using high-efficiency photothermal conversion
