Invisible Nano-wires: increases solar cell efficiency

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By making tiny wires that lie across the top of solar cells, US researchers find out solar cell can absorb more sunlight than they previously could. These conventional solar cells are panels with a square grid of wires which are rolled on top of itself. These wires are necessary for conduction of electrical charge absorb by cells. They may not like that they are really blocking cell’s capacity to absorb sunlight, but, in reality, they obstructs 5 to 10 percent of the light.

Vijay Narasimhan, one of the researchers from Stanford University said, “By using nanotechnology, we have developed a new way to make the upper metal contact invisible to incoming light. Our new technique could lower the cost of solar cell and improve its efficiency”. The team has developed a new method where a 16-nanometre gold thick film can place over a flat sheet of silicon, instead of using conventional wires. Puzzled with an array of Nano-sized holes, this film permeated with matching array of silicon Nanopillars, which comes up through metallic layer.

Thomas Hymel, one of the team member said, “We have immersed silicon and gold film together in a solution of hydrofluoric acid and hydrogen peroxide. After that, the gold film starts sinking immediately into the silicon substrate and silicon Nanopillars starts popping up through the holes in the film”. The advantage of this Nanopillar is, they come up through reflective surface of the metal and funnel light and, therefore, the energy comes from the underneath of silicon substrate. This system has come with an end result by energy gain standpoint, redirecting light through metal is almost same.

Narasimhan said,” in our design, near about two to three surface are covered with metal, still the reflection loss is only 3 percent. Having that much metal can increase conductivity and make the cell convert light into electricity more efficiently.” with the expectations of their Nano-wire sheet can boost the efficiency of solar cells from 20 to 22 percent, for that the researchers plan to test the performance of working cells in the real world.

Ruby Lai, a graduate student said, “Because of the shadow of silicon Nanopillars hides metal inside it, we call it by ‘covert contacts’. It doesn’t matter what type of metal researchers put inside it. It is nearly invisible to incoming light.”