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The promises of organic solar cells

In the race for renewable energy, organic solar cells are currently the subject of a considerable acceleration. Obtained easily at low cost and with low environmental impact, compatibility with flexible substrates, they allow to consider numerous applications: packaging, clothes, flexible displays, recharging cell phones or laptops. Teams from the Laboratory of Molecular Engineering of Angers (CNRS / Université d'Angers) and laboratory materials, surfaces and processes for catalysis (CNRS / Université Strasbourg 1) just to get a record performance solar cells basis of organic molecules. Their work is published online at the website of the Journal of Materials Chemistry.

Photovoltaic solar energy used to produce electricity by converting a portion of solar radiation with solar cells, connected them to form a photovoltaic module. Currently, commercial solar cells are composed of inorganic materials such as silicon.

Many international research aimed at developing solar cells made of organic semiconductor (based on carbon molecules). Although their performance is still well below those of cells based on crystalline silicon (about 5% performance against 15% for silicon cells), they offer multiple benefits. Unlike crystalline silicon whose production requires very high temperatures, their production involves a financial cost and low energy and low environmental impact, significant arguments when we talk about renewable energy. Moreover, their formatting with processes in solution (such as ink or paint) to cover large areas and flexible substrates (films, textiles).
Organic solar cells are not intended to compete with silicon, but to be used for special applications: packaging, clothes, flexible displays, recharging cell phones or laptops. However, in the longer term, they could contribute significantly to the photovoltaic conversion of solar energy, provided they invest heavily in research of new materials more efficient and more stable.

Over the past decade, most research focuses on the development of organic cells in which the active materials absorbing light are large chains of conjugated polymers. If these cells are the most successful to date, the use of polymers poses a number of problems: synthesis, purification, control of structure and molecular weight distribution of different chain lengths (polydispersity).

To circumvent these obstacles, the team of Jean Roncali Laboratory of Molecular Engineering Angers (CNRS / Université d'Angers) develop an original approach based on the replacement of the polymer molecules together by well-defined structure . While the yields of the first prototypes in 2005 were about 0.20%, a collaboration between the team and in Angers Raymond Ziessel Laboratory materials, surfaces and processes for catalysis (CNRS / Université Strasbourg 1 ), supported by the energy program of the CNRS, has led recently to achieve yields of 1.70%, which are among the highest so far for this cell type.

New classes of active materials specifically adapted to these cells are currently being synthesized in these laboratories. Researchers hope to improve their results very quickly. What envy of industrial ...