How NANO can achieve BIG things?

How NANO can achieve BIG things?

Bengaluru, India | Red Newswire | Dec 16, 2015 Last Updated at 02:35 PM IST.

As the world temperature is constantly increasing so is the pressure upon nations to reduce their carbon emissions and to look for alternative sources of energy is increasing. India stands 3rd among the list of nations who contribute largely to global emissions and thus the role of India in maintaining the world temperature below 2 degree Celsius becomes important.

One way of achieving this target is to opt for renewable sources of energy and India has already started making efforts in this way largely by allocating and setting up land for solar energy to be used. Amidst this effort you will be glad to hear that scientists, including one of Indian-origin, have developed a new technology that could significantly improve the efficiency and lower the cost of solar cells.

Researchers at Stanford University created silicon 'nanopillars' on solar cells to hide the reflective metal contact so that the funnel light can directly reach the semiconductor below.

"Using nanotechnology, we have developed a novel way to make the upper metal contact nearly invisible to incoming light," said study lead author Vijay Narasimhan, who conducted the work as a graduate student at Stanford University.

"Our new technique could significantly improve the efficiency and thereby lower the cost of solar cells," Narasimhan.

In most solar cells, the upper contact consists of a metal wire grid that carries electricity to and fro from the device. However, these wires also prevent sunlight from reaching the semiconductor.

"The more metal you have on the surface, the more light you block," said study co-author Yi Cui, an associate professor of materials science and engineering. Therefore, metals were decreasing the efficiency of the cells.

For the study, the researchers placed a 16nm-thick film of gold on a flat sheet of silicon. The gold film was riddled with an array of nanosized square holes, but to the eye, the surface looked like a shiny, gold mirror.

Optical analysis showed that the perforated gold film covered 65% of the silicon surface and reflected, on average, 50% of the incoming light.

They created nanosized pillars of silicon that "tower" above the gold film and redirect the sunlight before it hits the metallic surface.

The nanopillars were created using only one step.

"We immersed the silicon and the perforated gold film together in a solution of hydrofluoric acid and hydrogen peroxide," said graduate student and study co-author Thomas Hymel.

"The gold film immediately began sinking into the silicon substrate, and silicon nanopillars began popping up through the holes in the film," Hymel said.

Within seconds, the silicon pillars grew to a height of 330 nanometres, transforming the shiny gold surface to a dark red. This dramatic colour change was a clear indication that the metal was no longer reflecting light.

"As soon as the silicon nanopillars began to emerge, they started funnelling light around the metal grid and into the silicon substrate underneath," Narasimhan said.

By: Rishi Sharma @Rednewswire