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All lights on photovoltaic cells
A photovoltaic cell directly converts light energy into an electrical current. The cells are then assembled into photovoltaic modules (solar panels). Most solar panels are currently made of crystalline silicon and have a conversion efficiency of 12 to 17%. It is hoped this efficiency can be increased to 20%. In order to reduce costs – ultra pure crystalline silicon wafers are an expensive material – chemists are working on : the possibility of directly using less pure silicon, the use of thin silicon layers (1 to 10 micrometers) deposited in amorphous or microcrystalline form onto various less costly media such as glass, metal or ceramics, or even plastics, the use of inorganic materials other than silicon and lastly the use of organic materials made of polymers which are very inexpensive, biodegradable and easy to manipulate, thanks to their flexibility.
At present, the inorganic materials that can replace silicon are copper indium selenide (CIS) or cadmium telluride used in the form of thin layers deposited onto glass or plastic. The photovoltaic modules then achieve efficiencies of 11 to 13% which are getting closer to the performances of silicon modules. This area is currently booming.
The use of organic materials made of polymers which are very inexpensive, degradable and easy to manipulate, thanks to their flexibility, is also being considered. For the time being, they only achieve an efficiency of 3 to 5% and a limited service life (500 to 1000 hours). Subject to a more refined understanding and control of their aging mechanism, we can hope to see them on the market one day !
Finally, longer term studies are aiming to maximize the use of the theoretical possibilities of photovoltaic conversion towards very high efficiencies, using multijunctions, light concentration or even new concepts that could achieve efficiencies above 50% in the medium term.
Institut de recherche et de développement sur l’énergie photovoltaïque, CNRS-Chimie Paristech-EDF
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