According to an article published this month in Technology Review, a cheap new method of attaching mirrors to silicon produces very efficient solar cells that are inexpensive to manufacture. The technique could lead to solar panels that produce electricity for the average price of electricity in the US.
Suniva, a start-up company based in Atlanta, has developed solar cells that convert about 20% of the energy from light that falls on them into electricity. This figure is an increase from 17% of its previous solar cells and is close to the efficiency of the best solar cells on the market, but according to Ajeet Rohatgi, founder and CTO of the company, unlike other silicon solar cells Highly effective, Suniva's are made with low-cost methods. One of them is screen printing, a relatively cheap process and very similar to the screen printing used for printing T-shirts.
Until now, the high cost of solar cells has limited them to a marginal role in energy production, providing less than 1% of the world's electricity. Rohatgi estimates that the company's low-cost manufacturing techniques will allow solar power to compete with conventional sources, producing electricity for about 8-10 cents per kilowatt-hour (similar to the average cost of electricity in the US). and much lower than the prices of other markets).
Suniva cells are very effective because they can trap light, holding photons within the active material of the solar cell until the energy can be used to release electrons and generate an electrical current. The basic concept of catching light is not new. It depends on the texturing of the front surface of the silicon layer that forms the active material of the solar cell. Texturing creates different faces that redirect incoming light, refracting it so that instead of passing directly through the silicon, it travels along the silicon layer. Photons therefore stay longer in the material and have a better chance of being absorbed by atoms in the material. When that happens, the energy from the photons can release electrons which, in turn, are used to generate a current.
Light capture can be increased by pairing the textured surface with a reflective layer on the back of the silicon layer. The mirror keeps the light in the solar cell for longer, further increasing the number of electrons released. As a result, the silicon can be half as thick as usual and absorb the same amount of light. Using less of an expensive material directly reduces costs, but the method also allows solar cell manufacturers to make them with less pure and cheaper forms of silicon. In a conventional solar cell, which may have a 200 micron thick layer of silicon, impurities in the material can easily trap electrons before they reach the surface and escape to generate current. In contrast, in a layer of silicon just 100 microns thick, electrons travel a shorter distance, making them less likely to encounter an impurity before escaping. Lower grade silicon is much cheaper and easier to work with than the highly refined silicon commonly used in solar cells.
Source: Technology Review