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Molybdenum disulfide holds promise for light absorption

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Mechanics know molybdenum disulfide (MoS2) as a useful lubricant in aircraft and motorcycle engines and in the CV and universal joints of trucks and automobiles. Rice University engineering researcher Isabell Thomann knows it as a remarkably light-absorbent substance that holds promise for the development of energy-efficient optoelectronic and photocatalytic devices.

"Basically, we want to understand how much light can be confined in an atomically thin semiconductor monolayer of MoS2," said Thomann, assistant professor of electrical and computer engineering and of materials science and nanoengineering and of chemistry. "By using simple strategies, we were able to absorb 35 to 37 percent of the incident light in the 400- to 700-nanometer wavelength range, in a layer that is only 0.7 nanometers thick."

Thomann and Rice graduate students Shah Mohammad Bahauddin and Hossein Robatjazi have recounted their findings in a paper titled "Broadband Absorption Engineering To Enhance Light Absorption in Monolayer MoS2," which was recently published in the American Chemical Society journal ACS Photonics. The research has many applications, including development of efficient and inexpensive photovoltaic solar panels.

"Squeezing light into these extremely thin layers and extracting the generated charge carriers is an important problem in the field of two-dimensional materials," she said. "That's because monolayers of 2-D materials have different electronic and catalytic properties from their bulk or multilayer counterparts."

Thomann and her team used a combination of numerical simulations, analytical models and experimental optical characterizations. Using three-dimensional electromagnetic simulations, they found that light absorption was enhanced 5.9 times compared with using MoS2 on a sapphire substrate.

"If light absorption in these materials was perfect, we'd be able to create all sorts of energy-efficient optoelectronic and photocatalytic devices. That's the problem we're trying to solve," Thomann said.

She is pleased with her lab's progress but concedes that much work remains to be done. "The goal, of course, is 100 percent absorption, and we're not there yet."

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A copy of the paper is available at: http://pubs.acs.org/doi/abs/10.1021/acsphotonics.6b00081

Thomann lab homepage: http://thomanni.rice.edu/

Related photonic research from Rice:

Rice researchers demo solar water-splitting technology — Sept. 4, 2015 http://news.rice.edu/2015/09/04/rice-researchers-demo-solar-water-splitting-technology/

Rice's Thomann wins CAREER grant to study photocatalysis — June 19, 2014 http://news.rice.edu/2014/06/19/rices-thomann-wins-career-grant-to-study-photocatalysis/

This release can be found online at news.rice.edu.

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Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation's top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,910 undergraduates and 2,809 graduate students, Rice's undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for best quality of life and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger's Personal Finance. To read "What they're saying about Rice," go to http://tinyurl.com/RiceUniversityoverview.

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