Power Generation

An antireflective coating developed by researchers at Rensselaer Polytechnic Institute in the US promises to give a major boost to the efficiency of solar cells.

A typical solar cell made out of silicon absorbs only around 67% of the sunlight hitting it. But coating the same solar cells with the antireflective coating developed by Shawn-Yu Lin and his team increases that amount to over 96%.

The antireflective coating increases absorption across the whole spectrum of sunlight and from any angle. This is an added bonus, as it could make redundant the need to angle solar panels toward the direction of sunlight.

“To get maximum efficiency when converting solar power into electricity, you want a solar panel that can absorb nearly every single photon of light, regardless of the sun's position in the sky,” explains Lin. “Our new antireflective coating makes this possible.”

The coating consists of seven very thin layers of tiny angled rods made out of silicon and titanium dioxide. The layers are just 50-100 nm thick – where a nanometre is one-billionth of a meter. The nanorods, as they are called, are very good at capturing photons of light – and making sure that they don’t escape again through reflection.

The forests of nanorods are attached to silicon solar cells using a special technique called chemical vapour deposition. The coating can also be put onto other materials used for solar cells including III-V semiconductors and cadmium telluride.

For further information:
Mei-Ling Kuo, David J. Poxson, Yong Sung Kim, Frank W. Mont, Jong Kyu Kim, E. Fred Schubert, and Shawn-Yu Lin. Realization of a near-perfect antireflection coating for silicon solar energy utilization. Optics Letters (2008) 33 (21), 2527-2529

Photo credit: Rensselaer/Shawn Lin