Michel Rollier be him also forced lower pressureThe Sadef company which operates the network of stores MrOur two companies are virtually not competingIn Paris the CAC 40 index was unscrewed 5This is why it would not delay the relocationSo far they used the Internet to their imageIn Rock' n ' roll changing constantly cityToday the case could go back to square one Printing money it means clearly reflationThe next trilateral summit should be held in Poland in 2008This summer, the solar energy hit very hard. The American laboratory of renewable energy (NLREL) announced designed a photovoltaic cell in 41 of performance. In other words, researchers are no longer very far from whether transforming half of solar electricity is happening on Earth. At Valencia a week ago, the European Conference on solar energy bringing together 4,000 researchers, other records fell. Virtually all photovoltaic technologies are concerned. These beasts of race is not only the achievements of laboratories, they suggest a rapid evolution of these technologies in their wake. "It is a grand cru scientific, believes Daniel Lincot, Director of the laboratory of analytical chemistry and electrochemistry and President of the Congress of Valencia." We see out new advanced concepts laboratory, in parallel with research efforts to reduce the prices of Silicon technologies. 
All researchers today have their eyes screwed on the theoretical maximum efficiency: 84 of the energy of the photons could be convertible into electricity. In this race of substantive strategies differ. Some technologies produce high but a prohibitive cost performance. Other laboratories are contrary to economic processes to make technology more efficient.
Economy of material
The optimum is currently held by the crystalline silicon technology, which truste 94 of the market. The best laboratories, such as Sanyo or Sunpower, exceed 20 of performance, and plants are just less efficient products. But this sector uses 200 microns of thickness microelectronics industry silicon wafers. They are so expensive to manufacture, and their availability is limited.
Thin film cells could take up the slack in the classical sector, because they approach of industrialization. They consist of a substrate of type coated glass with a layer of a few microns of amorphous silicon. The economy of material offers lower cost of production three times, but their yields fall around ten percent.
Some laboratories and industry now want to quit habit of his addiction to Silicon photovoltaics. They resumed but the concept of thin films with coatings of alternative materials. Both substances have emerged among the already tested hundreds: CdTe and CIGS (copper-indium-gallium-selenium). Daniel Lincot laboratory works on the last track and currently approaching 20 performance. This technology of deposition is another interest to produce large sensor surface, while Silicon is still stationed in the small cakes. Several manufacturers of flat screens, masters in the art of the deposition of layers, currently converting in this sector. Other sectors as the industrialists of the tin coating also seek to exploit their know-how. The Californian Nanosolar, uses him, printing processes to get its first flexible cells. Such production capacity investment promises significant cost reductions. The first copies of 30 cm wide cells however upper 7 performance.
To browse through tens of percent between them theoretical performance, researchers explore more radical paths. Current cells know transform into electricity that a small part of the spectrum of light between the near-ultraviolet and infrared. This is because a photovoltaic material knows that retrieve a specific electron burst when they are excited by light. All the photons that have a lower wavelength does not allow electrons of the material to a current: they fall back into their holes. Those who have a superior energy deliver only the absorbable burst by the material.
To broaden the spectrum of the cells, the researchers much inventiveness. The first way is to stack several photovoltaic layers; each specialized in a spectrum. It is three stacks that NREL has reached its record of 41 of performance.
New routes
Other laboratories rely on a filter above the cell to compress the wavelengths of incident photons to return to the "shoe horn" in the spectrum of the photovoltaic material. But the Congress of Valencia crowned a more promising approach, that of the Australian researcher Martin Green. It integrates into the silicon to silicon dioxide nanoparticles to quantum behaviour. This material opens the infrared band to the photovoltaic effect.
Finally is the strategy of organic cells (plastic). This route is very low cost but its yields remain low. The Ecole polytechnique fédérale de Lausanne however is to unveil a prototype of dye cell that exceeds the 11, unimaginable feat a few years ago. This technology is the nearest plant photosynthesis, the process perfect conversion of solar energy. Plants convert photons with dye as the chlorophyll molecules who know how to store energy in their electrons. Organic cells are coated with porous film with a very thin layer of particles of pigment in contact with an electrolyte solution. When a photon strikes the cell, it produces a negative charge in the pigment and a positive charge in the electrolyte, leading to a current. To boost this relatively small photovoltaic effect, scientists had the idea to increase the interfaces between the dye and the electrolyte. Prototypes are thus active surfaces whose geometry reminds the lungs or trees. These live organizations know maximize contact surfaces, like Fractals. It is the time chemists, and non-physicists who are most advanced in this field.
Currently, it is impossible to know which of these technologies will cover term roofs and the fields in the 21st century. "Do not oppose them, the competition remains open," promises, optimist, Daniel Lincot.
