Stanford University scientists have created the thinnest, most efficient absorber of visible light on record. The nanosize structure, thousands of times thinner than an ordinary sheet of paper, could lower the cost and improve the efficiency of solar cells, according to the scientists. Their results are published in the current online edition of the journal Nano Letters.

 

Thinner solar cells require less material and therefore cost less. The challenge for researchers is to reduce the thickness of the cell without compromising its ability to absorb and convert sunlight into clean energy.

 

For the study, the Stanford team created thin wafers dotted with trillions of round particles of gold. Each gold nanodot was about 14 nanometers tall and 17 nanometers wide.

 

In the experiment, postdoctoral scholar Carl Hagglund and his colleagues were able to tune the gold nanodots to absorb one light from one spot on the spectrum: reddish-orange light waves about 600 nanometers long.

 

The results were record-setting. “The coated wafers absorbed 99 percent of the reddish-orange light," Hagglund said, keeping in mind that these wafers are about 1,000 times thinner than commercially available thin film solar cell absorbers. The next step for the Stanford team is to demonstrate that the technology can be used in actual solar cells.

 

The scientists are also considering nanodot arrays made of less expensive metals such as silver. Gold was used in this experiment for its chemical stability.