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[Summer series] Pere Roca i Cabarrocas - The sun also sets

Pere Roca i Cabarrocas, director of the Laboratory of Physics of Interfaces and Thin Films, assembles films of atoms from the bottom up, growing thin layers for photovoltaic solar panels.

©Silvère Leprovost

As a teenager, Pere Roca i Cabarrocas built houses with his father, a mason, and out of this experience grew a passion for building things from the ground up.  He now works on objects of a much smaller scale, and assembles films of atoms from the bottom up, growing thin layers for photovoltaic solar panels.

“It is satisfying to conduct research that eventually leads to real products”, admits Pere Roca, director of the Laboratory of Physics of Interfaces and Thin Films (LPICM). His attraction to solar energy is rooted in a childhood steeped in nature. Growing up in a Catalonian village in Spain, surrounded by fields, forests and rivers, he developed his ecological views during a period marked by budding opposition to nuclear energy. For the scientist, photovoltaic electricity represents “an elegant and interesting way to harness energy”. Recipient of the CNRS silver medal in 2011, Pere Roca is responsible for the discovery of polymorphous silicon, a form of silicon offering greater stability and a higher yield than the amorphous silicon previously used in the design of thin-film photovoltaic panels.

International collaborations

His first work on solar cell devices dates back to 1985 during his doctoral research in the laboratories of École Polytechnique on a scholarship paid by the Catalan government. After a subsequent post-doctoral stay at Princeton, he drew inspiration from the methods of teamwork he witnessed in the United States and began applying them in France. “Innovation comes through travel and exchange”, comments the scientist, who has continued to interact with researchers around the world at international conferences and meetings. This year, he was selected by the Nara Institute of Science and Technology (NAIST) in Japan to be a visiting professor as part of the new international solar energy laboratory, created in partnership with École Polytechnique. Indeed, his involvement with this institute dates back to the 1990s, as is evidenced by a photo hanging on the wall of his office showing him in Nara surrounded by Japanese scientists 25 years ago.

An energy revolution

At École Polytechnique, where he studies silicon thin films and their applications (including in the field of solar panels), Pere Roca’s research has crossed disciplines and brought him to work with several laboratories, including those of plasma physics, condensed matter physics, and organic synthesis. With his team, he has developed techniques for depositing silicon thin films that achieve a 100 to 500 times reduction in the amount of silicon used in solar panels. Another discovery is a unique method for the bottom-up "epitaxial" growth of crystalline silicon; by using a cold plasma-assisted deposition technique, one reduces the necessary process temperature from 1000°C to 200°C, thereby dramatically reducing energy consumption.

“We are experiencing an energy revolution. Solar power’s share of global electricity generation is growing at a very high rate. The field of possibilities is ever-widening”, he says with enthusiasm. Already the researcher is imagining transparent photovoltaic surfaces replacing windows on houses.

Find all the portraits of researchers of our summer series, here.