Solar cells are semiconductors that are sandwiched between metal contacts, looking rather like a metal wire grid, that carries the electrical current. However, the shiny metal on top of the cell reflects sunlight away from the semiconductor, thereby reducing the cell’s efficiency. Scientists at Stanford University have now discovered a way in which to hide the reflective upper contact and enable light to be funnelled directly to the semiconductor. This in turn will help to increase the efficiency of a solar cell, as well as potentially leading to new designs and fabrications in solar cell development.
The findings of the research team have now been published in the journal ACS Nano.
“Using nanotechnology, we have developed a novel way to make the upper metal contact nearly invisible to incoming light” said Vijay Narasimhan, lead author of the study lead author. “Our new technique could significantly improve the efficiency and thereby lower the cost of solar cells.”
Study co-author Yi Cui, an associate professor of materials science and engineering, added that the more metal there is on the surface of the cell, the more light is blocked.
The Stanford team placed a 16-nanometer-thick film of gold conducting metal on a flat sheet of silicon. They found that the film reflected 50 percent of the incoming light and reasoned that if they could hide the film, more light would reach the semiconductor beneath it. Their solution was to create nanosized pillars of silicon that reach above the gold film and redirect the sunlight before it hits the metallic surface.
Cui and Narasimhan will be discussing the new nanopillar technology at the fall meeting of the Materials Research Society in Boston on December 1st.
Image: From left; Vijay Narasimhan, Ruby Lai and Thomas Hymel
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