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Black Silicon
A simple, inexpensive treatment could reduce the cost of solar power

Source: “Efficient Black Silicon Solar Cell with a Density-Graded Nanoporous surface”
Howard Branz et al.
Applied Physics Letters 95:123501-123503

Results: A simple chemical technique can create a highly antireflective surface on silicon solar cells. The new method for making this so-called “black silicon” results in cells that convert 16.8 percent of the light that hits them into electricity, which is comparable to the efficiency of many commercial solar cells. It’s a significant improvement over the previous record for solar cells made of black silicon, which was 13.9 percent.

Why it matters: The technique could make crystalline solar cells, the most common type, cheaper to make, because it is less expensive than producing the anti­reflective coatings now used to keep photons from bouncing off the cells and going to waste. Previously developed methods for making black silicon may be impractical for large-scale manufacturing because they are more complex or involve slow and costly equipment. The new research demonstrates that the antireflective surface can be readily made using equipment already on hand at solar-cell factories.

Methods: The researchers submerged a silicon wafer in an acidic solution containing trace amounts of gold. Chemical reactions generated gold nanoparticles, which then catalyzed reactions that etched holes of varying depths into the wafer. This created a porous structure that blurs the boundary between the surrounding air and the bulk silicon, reducing reflection.

Next steps: The researchers are working to increase the cell efficiencies further and performing more detailed calculations to determine how the process will affect the cost of solar power.

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Credit: Wei Wu

Tagged: Energy, Materials

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