Silver Makes Solar Cells More Efficient
According to an article from Economist, Australian scientists have been using silver to redirect the light that falls onto the surface of a cell in such a way that all colours are efficiently absorbed. The question is: how’s that going to help with making Solar energy more affordable? The report says that the quantity of silver is so small that its worth it.
When struck by light, the electrons in an atom of silver vibrate in a way that causes them to radiate small amounts of light themselves. If the atom in question is in a small particle on the surface of a piece of silicon, the result is what is known as a surface plasmon. This is a type of electromagnetic wave (ie, the same type of wave as a light wave). However, as its name suggests, it runs parallel to the surface of the material that is propagating it, rather than penetrating this material.
By travelling horizontally in this way, a plasmon passes through more of the solar cell’s silicon than any incident beam from the sun could. In effect, the cell has been turned on its side and made much thicker. That gives it the opportunity to absorb, and thus convert into electricity, most of the red light falling on it, as well as the blue. Indeed, Dr Catchpole and Dr Polman report in Optics Express that their system increases the absorption of red light tenfold—bringing the efficiency of thin cells much closer to that of the traditional sort.
