The Likely Candidate for a Next-Generation Solar Cell

When someone hears that Ricoh is engaged in joint development with the Japan Aerospace Exploration Agency (JAXA), the usual response is probably "what on earth are they working on together?" Are they developing a copier that can be used on a space station? Space development certainly gives the impression of large national projects to create rockets or artificial satellites. To get to the bottom of this, I visited JAXA's Sagamihara Campus, located in Sagamihara, Kanagawa Prefecture.

When I arrived at JR Fuchinobe Station, which is the nearest station to the campus, large panels depicting the Japanese manga comics Space Brothers and Galaxy Express 999 leapt out at me. With my thoughts full of space, I set out on the 20-minute walk. In time, I arrived at the Sagamihara Campus. Since this was a special open day to the general public, a long line was formed before the gate opened. Boys wearing home-made blue suits (styled after the attire worn by astronauts) and middle-aged and older men with NASA (National Aeronautics and Space Administration) logo T-shirts created a sense of pageantry as a unique air of excitement spread throughout.

The Sagamihara Campus is an important hub of space development in Japan on par with JAXA's Tsukuba Space Center in Tsukuba, Ibaraki Prefecture. Taking over from the former Institute of Space and Astronautical Science, this is where JAXA pursues research into things such as science satellites and small rockets.

Full-scale model of an M-V Rocket at the JAXA Sagamihara Campus

The centerpiece of the special open day was a model of the much-talked-about Hayabusa 2 asteroid explorer. Hayabusa 2 plans to land on the asteroid Ryugu, collect samples and return to Earth. Shortly before my visit, news hit that Hayabusa 2 had arrived above Ryugu, and the exhibit was packed with onlookers.

The first-generation Hayabusa was the predecessor of Hayabusa 2. Overcoming recurring problems it arrived at the asteroid Itokawa and managed to return to Earth in June 2010. Its mission generated so much interest that movies were made about it, and its successor has understandably attracted a lot of attention.

Model of the Hayabusa 2 asteroid explorer

The valuable technologies and knowledge gained in the process of space development have also ended up being utilized in consumer products. That's due to all the potential that comes from developing things to withstand the harsh environment of space. For example, NASA pump technologies used in the space shuttle have been applied to artificial hearts embedded in human bodies, while air purifiers used in the International Space Station (ISS) have been adopted in systems to extend the life of products in grocery stores and elsewhere.

On the other hand, recently a growing number of developments have traveled in the other direction. In other words, there have been efforts to make use of consumer products to develop artificial satellites and rockets. In the past, JAXA has developed an ultra-small rocket equipped with consumer semiconductor components used in home appliances.

In fact, the joint development Ricoh and JAXA are undertaking in is one such endeavor. You may remember the buzz last autumn about a Japanese person who was considered a potential winner of the Nobel Prize in Chemistry. This was Specially Appointed Professor Tsutomu Miyasaka of Toin University of Yokohama.

Professor Miyasaka discovered that special crystals known as perovskites have properties as semiconductors and can be applied to solar cells. Due to this accomplishment, Professor Miyasaka was one of the scientists chosen as a strong candidate for receiving the Nobel Prize in Chemistry by a U.S.- based academic information firm. Although he was passed over for the prize this year, expectations have grown among the people involved.

A schematic diagram showing the typical structure of a perovskite-based solar cell
Source: Researcher Yu Miyazawa

In short, a perovskite solar cell is the likely candidate for a thin and low-cost next-generation solar cell. Since the materials can be obtained easily, costs can be kept down, and as the materials can be applied to surfaces such as film to be made thin, it can be freely folded and is extremely lightweight. The cells can be fabricated much like printing, without the need to use large-scale equipment. For these reasons, the prospect of affixing solar cells to the surfaces of car bodies, building walls or even clothing to generate electricity is no longer the stuff of dreams.

Things might have just clicked for some of you when you read "much like printing." In fact, it is these very perovskite solar cells that are the subject of the joint research being conducted by Professor Miyasaka together with JAXA and Ricoh. They are applying the technologies used in copiers and printers to develop the likely candidate for a low-cost and lightweight next-generation solar cell.

This raises the question of why JAXA would be interested in perovskite. I interviewed Researcher Yu Miyazawa at the special open day venue.

Yu Miyazawa
R&D Staff of Research Unit I,
Research and Development Directorate and Sounding Rocket Research and Operation Group,
Institute of Space and Astronautical Science

Miyazawa jointed JAXA in 2012.
She is involved with research into the power supply systems of scientific satellites,
sounding rockets and solar cells.

― What makes a perovskite solar cell special?

First of all, compared with solar cells that have been installed in artificial satellites to date, they can be manufactured more easily and at a lower cost. On top of that, since perovskite crystals just a few hundred nanometers thick are able to absorb light, the solar cells can be made very thin.

Reducing weight by making things thinner is directly connected to lower launch costs. Having minimal deterioration even when solar cells are exposed to strong radiation in outer space, and being able to generate electricity in an environment with minimal light are also significant benefits. Another appeal is the high efficiency at which these solar cells can convert solar energy into electrical energy.

For example, an artificial satellite flying to a planet that is far away from the sun will have to maintain power with only a small amount of light. Some U.S.-made satellites have used nuclear power for this task, but this isn't practical for Japan. That's why producing solar cells that are light, low-cost and resilient against radiation are preferred, and perovskite solar cells fit the bill.

― Why is the joint research being conducted with Ricoh?

At the moment there are signs of changing trends in space development. In the past, it was usual to use dedicated components for the materials used in space. That's because reliability was given top priority, whatever the cost. Sometimes the cutting-edge technologies developed in this way have made their way into consumer products.

However, in recent years, we have started to see the reverse trend. Technologies that private companies have already commercialized are being repurposed for space development as part of efforts to reduce costs and drive innovation. To facilitate this, JAXA established the Space Exploration Innovation Hub Center. Ricoh is participating in this business.

Ricoh has strong connections with perovskite solar cells such as joint research with Nobel Prize candidate Professor Miyasaka and a lot is expected from these activities. What's more, Ricoh is among only a handful of companies with experience reaching the practical level with dye-sensitized solar cells (DSSC), where the roots of perovskite solar cells lie. It was because of this technological edge and its product development capabilities that we wanted to engage in joint research with Ricoh.

Panel display about the Space Exploration Innovation Hub Center at the JAXA Sagamihara Campus Special Open Day

― Tell us more about the Space Exploration Innovation Hub Center.

The center works with companies, universities and other organizations on challenges that show promise in terms of commercialization or the creation of innovative technologies. By proactively incorporating the technologies of private companies not related to the space industry and engaging in further technological development, we aim to achieve innovation on the ground and apply the fruits of that research to future space exploration.

We are inviting private companies that are willing to provide us with technical information. We then narrow down the research themes to be started on based on the technical information we can gather, and recruit participants for the joint research.

― Why did you decide to work at JAXA?

I took part in a tour of the Tsukuba Space Center on a high school trip. At the time, flight components that had yet to depart into space for the International Space Station (ISS) where at the center. I was struck by how cool it all looked, and before I knew it, I had chosen a career related to space.

Front gate of the JAXA Sagamihara Campus