Solar cell efficiency improved by 50% with anti-reflection coating (MIT Researchers)

November 26 2008 / by Garry Golden
Category: Energy   Year: 2016   Rating: 6 Hot

What happened? MIT OLED
MIT researchers are rethinking how light can be manipulated within solar cells.  They have applied an antireflection coating, a novel combination of multi-layered reflective coatings and a tightly spaced array of lines to the backs of ultrathin silicon films to boost the cells' output by as much as 50 percent.  [No official statement has been released on original vs improved efficiency level.]  

The coatings on the back of the solar cell force the light to bounce around longer inside the thin silicon layer, giving it time to deposit its energy and produce an electric current. "Without these coatings, light would just be reflected back out into the surrounding air" said Peter Bermel, an MIT postdoctoral physics researcher.

"It's critical to ensure that any light that enters the layer travels through a long path in the silicon," Bermel said. "The issue is how far does light have to travel [in the silicon] before there's a high probability of being absorbed" and knocking loose electrons to produce an electric current.

Why is this important to the future?
Depending on the range of its applications, this type of breakthrough could transform solar efficiencies for traditional crystalline (glass substrate) solar cells as well as thin film (carbon substrate) solar. 

While we invest in commercializing solar energy systems, we must not turn our backs on funding basic science that can yield fundamental breakthroughs.   "The simulated performance was remarkably better than any other structure, promising, for 2-micrometer-thick films, a 50 percent efficiency increase in conversion of sunlight to electricity," said Lionel Kimerling, the Thomas Lord Professor of Materials Science and Engineering, who directed the project.

The breakthrough also confirms the value of applying computational processing power for testing materials used to improve alternative energy technologies. 

The MIT team used advanced computer systems to run thousands of simulations that tested variations in the spacing of lines in the grid, the thickness of the silicon and the number and thicknesses of reflective layers deposited on the back surface. "We use our simulation tools to optimize overall efficiency and maximize the power coming out," Bermel said.

According to MIT, the work is just a first step toward actually producing a commercially viable, improved solar cell.  But "If the solar business stays strong," Kimerling said, "implementation within the next three years is possible."

Eureka Press release

The Electronic Materials Research Group at MIT (EMAT) is the research laboratory led by Lionel C. Kimerling, Thomas Lord Professor of Materials Science & Engineering.

MIT Image Credit

(Ex. Image Anti Reflection film)

About research team by David Chandler, MIT News Office:
In addition to Kimerling, Bermel and Zeng, the work was done by John Joannopoulos, the Francis Wright Davis Professor of Physics, and by research engineer Bernard A. Alamariu, research specialist Kurt A. Broderick, both of the Microsystems Technology Laboratories; postdoctoral associate Jifeng Liu; Ching-yin Hong and research associate Xiaoman Duan, both of the Materials Processing Center. Funding was provided by the Thomas Lord Chair in Materials Science and Engineering, the MIT-MIST Initiative, the Materials Research Science and Engineering Center Program of the NSF and the Army Research Office through the Institute for Soldier Nanotechnologies.

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