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Tech Developed to Double Efficiency of Nanowire Solar Cells by Coating Dielectrics
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Tech Developed to Double Efficiency of Nanowire Solar Cells by Coating Dielectrics
  • By Jung Suk-yee
  • February 3, 2015, 08:00
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Left: Silicon nanowire solar cell coated with silicon nitride shell. Middle: Photoelectric current of silicon nanowire solar cell increases up to 80% with silicon nitride. Right: Optical antenna effect before and after silicon nitride shell.
Left: Silicon nanowire solar cell coated with silicon nitride shell. Middle: Photoelectric current of silicon nanowire solar cell increases up to 80% with silicon nitride. Right: Optical antenna effect before and after silicon nitride shell.

 

A Korean research team has successfully developed a tech to coat a dielectric material that can cheaply double the efficiency of silicon nanowire solar cells. 

Kim Sun-kyung, professor of the Department of Applied Physics at Kyung Hee University, announced on Feb. 2 that a joint research team consisting of Korean and U.S. scientists has succeeded in doubling the efficiency of nanowire solar cells by coating them with a dielectric material. The study was conducted in collaboration with James F. Cahoon, professor of the Department of Chemistry at the University of North Carolina, and others.

Nanowire solar cells are made using a silicon nanowire with a 200 nm diameter and a dozens of µms in length in the part that changes light into electricity, instead of a silicon film. Since they cause a light-trapping optical antenna effect, nanowire solar cells can absorb more than twice as much light as thin-film photovoltaic cells. However, the nanowire solar cell cannot absorb a large amount of light, owing to its threadlike structure, making it inferior to thin-film photovoltaic cells in terms of light absorption. 

The research team made a 200 nm thick solar cell using nanowire, and coated it with Si₃N₄ using plasma-enhanced chemical vapor deposition to ensure a 50 nm thickness, thereby creating a nanowire solar cell with a new structure. 

The optical conversion efficiency of the newly-developed solar cell was 4 percent, a two-fold increase from existing nanowire solar cells. 

The outermost dielectric layer of nanowire refracted light probably caused nanowire to absorb more light, according to the research team. They explained that if this kind of nanowire solar cell is made with a thickness of existing thin-film photovoltaic cells, it will be possible to increase its efficiency to the level of already-commercialized products. 

Professor Kim said, “Our study was able to double the optical absorption rate of nanowire solar cells with low cost.” He added, “This method does not change the existing process. An improvement in the quality of nanowires will make it possible to use this technique instantly.”

The research findings were published online in the Jan. 15 issue of Nano Letters, a monthly scientific journal published by the American Chemical Society.