New surface treatment boosts efficiency of photovoltaic cells

March 25th, 2009 - 5:33 pm ICT by ANI  

Washington, March 25 (ANI): Researchers at the Georgia Institute of Technology have developed a surface treatment that boosts the light absorption of silicon photovoltaic cells in two complementary ways.

The surface treatment increases absorption both by trapping light in three-dimensional structures and by making the surfaces self-cleaning allowing rain or dew to wash away the dust and dirt that can accumulate on photovoltaic arrays.

Because of its ability to make water bead up and roll off, the surface is classified as superhydrophobic.

The more sunlight that goes into the photovoltaic cells and the less that reflects back, the higher the efficiency can be, said C.P. Wong, Regents professor in Georgia Techs School of Materials Science and Engineering.

Our simulations show that we can potentially increase the final efficiency of the cells by as much as two percent with this surface structure, he added.

The silicon etching treatment mimics the superhydrophobic surface of the lotus leaf, which uses surface roughness at two different size scales to create high contact angles that encourage water from rain or condensation to bead up and run off.

As the water runs off, it carries with it any surface dust or dirt which also doesnt adhere because of the unique surface properties.

In the silicon surface treatment, the two-tier roughness created with both micron- and nano-scale structures works in the same way as the lotus leaf, minimizing contact between the water or dust and the surface, Wong noted.

When a water droplet reaches the surface, it sits on top of this two-tier roughness and only about three percent of it is in contact with the silicon, he explained.

A normal silicon surface reflects a lot of the light that comes in, but by doing this texturing, the reflection is reduced to less than five percent, said Dennis Hess, a professor in the Georgia Tech School of Chemical and Biomolecular Engineering.

As much as 10 percent of the light that hits the cells is scattered because of dust and dirt of the surface. If you can keep the cells clean, in principle you can increase the efficiency. Even if you only improve this by a few percent, that could make a big difference, he added.

According to Wong, even in desert areas where constant sunlight provides ideal conditions for photovoltaic arrays, nighttime dew should provide enough moisture to keep the cells clean. (ANI)

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