Traditional
photovoltaic cells are made from thin sheets of
silicon covered by glass plates. In the GreenSun process, it is only the outer edges of the
glass plates that are covered by thin strips of silicon. The physicists and chemists at GreenSun, led by
Renata Reisfeld, coat the glass with metallic
nanoparticles and
dyes to cause the sunlight falling on the glass to diffuse sideways toward the edges where the silicon strips turn it into electricity. A mixture of dyes is used to capture and absorb a wide spectrum of available light. Having absorbed the sunlight, the fluorescent dyes then re-radiate it. Interaction with the metallic nanoparticles turns light into a form of
electromagnetic radiation known as
surface plasmons. The surface plasmons propagate over the glass surface and are intercepted by the silicon strips at the edges. The company would not reveal which metals are used in the process. Because the process uses less silicon, it is far less expensive than conventional
photovoltaic modules. It is also more efficient. In a conventional photovoltaic cell, much of the sun's energy is lost as heat because the energy of light varies across the spectrum (red light is less energetic than blue, for example). Only a particular amount of energy is needed to knock an
electron free from the silicon
atoms. If the sunlight is more energetic than necessary, more energy than usual is lost as heat. Sunlight scatters its energy, but the dye/nanoparticle mix in the GreenSun process delivers plasmons and
photons of the right energy to knock electrons free more efficiently. ==Economics==