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Home » Featured Research » Recent Research Topic from Functional Organic Chemistry Laboratory: Development of Organic Thin-Film Solar Cell Materials

Recent Research Topic from Functional Organic Chemistry Laboratory: Development of Organic Thin-Film Solar Cell Materials

Posted on : October 2, 2018

Currently, as a clean renewable energy that replaces fossil fuels, silicon solar cells (inorganic solar cells) are installed and introduced in various places, like solar panels installed in roofs of houses. However, silicon solar cells have problems such as high fabrication cost, limited installation location due to the nature of heavy and hard solar cells.

On the other hand, organic thin-film solar cells composed of organic substances are all composed of light organic substances for generating electricity, and research is proceeding as next-generation renewable energy. Since the power generation layer can be produced by "printing" the light absorbing ink onto a thin plastic film, it can be mass-produced at a very low price. Also, because it is made of very soft organic matter, you can realize a solar cell that will not break even if it is bent or stretched. As a result, it can also be installed on curved surfaces such as building walls and car side, so there are advantages such as choosing the installation location. Moreover, it can be used for dimmer and interior of window from its high design. However, since energy conversion efficiency is lower than that of silicon solar cells, organic thin film solar cells have not yet been put to practical use. It is said that energy conversion efficiency exceeding 15% is required for practical application.

In order to improve the energy conversion efficiency of the organic thin film solar cell, it is necessary to develop a new material among the organic materials constituting the power generation layer, which shows higher performance than the materials developed so far. The power generation layer of the organic thin-film solar cell is a hole (a hole formed by electrons in a substance escaping, behaving like a particle having a positive charge due to the loss of an electron having a negative charge.) A p-type semiconductor that transports holes in the opposite direction to the flow of electrons) and an n-type semiconductor that transports electrons. At the interface where these two materials are in contact with each other, absorbed sunlight Is converted into electrons and holes, and it can be taken out as a current. In order to increase the energy conversion efficiency, it is important that this p-type semiconductor and n-type semiconductor absorb as much sunlight as possible and let the current flow as quickly as possible. In our research group, we are developing p-type semiconductors that show high performance among the materials used for the power generation layer of organic thin film solar cells. In particular, we have independently developed a new skeleton that has never existed, succeeded in developing new materials through unique synthetic reactions, achieving a high conversion efficiency of 9% at this stage.

Reseach Papers

“Phenanthrodithiophene (PDT)−Difluorobenzothiadiazole (DFBT) Copolymers: Effect on Molecular Orientation and Solar Cell Performance of Alkyl Substitution onto a PDT Core”, H. Mori, R. Takahashi, K. Hyodo, S. Nishinaga, Y. Sawanaka, and Y. Nishihara, Macromolecules 201851, 1357−1369.

DOI:10.1021/acs.macromol.7b02734

“Alkoxy-Substituted Anthra[1,2‑c:5,6‑c’]bis([1,2,5]thiadiazole) (ATz): A New Electron-Acceptor Unit in the Semiconducting Polymers for Organic Electronics”, H. Mori, S. Nishinaga, R. Takahashi, and Y. Nishihara, Macromolecules 201851, 5473−5484.

DOI:10.1021/acs.macromol.8b01230

Functional Organic Chemistry: Nishihara Lab.

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