Featured Research

from universities, journals, and other organizations

Forcing mismatched elements together could yield better solar cells

Date:
September 8, 2010
Source:
University of Michigan
Summary:
In what could be a step toward higher efficiency solar cells, researchers have invalidated the most commonly used model to explain the behavior of a unique class of materials called highly mismatched alloys.

In what could be a step toward higher efficiency solar cells, an international team including University of Michigan professors has invalidated the most commonly used model to explain the behavior of a unique class of materials called highly mismatched alloys.

Highly mismatched alloys, which are still in the experimental stages of development, are combinations of elements that won't naturally mix together using conventional crystal growth techniques. Professor Rachel Goldman compares them to some extent to homogenized milk, in which the high-fat cream and low-fat milk that would naturally separate are forced to mix together at high pressure.

New mixing methods such as "molecular beam epitaxy" are allowing researchers to combine disparate elements. The results, Goldman says, are more dramatic than smooth milk.

"Highly mismatched alloys have very unusual properties," Goldman said. "You can add just a sprinkle of one element and drastically change the electrical and optical properties of the alloy."

Goldman is a professor in the departments of Materials Science and Engineering, and Physics. Her team included other U-M physicists and engineers as well as researchers from Tyndall National Institute in Ireland.

Solar cells convert energy from the sun into electricity by absorbing light. However, different materials absorb light at different wavelengths. The most efficient solar cells are made of multiple materials that together can capture a greater portion of the electromagnetic radiation in sunlight. The best solar cells today are still missing a material that can make use of a portion of the sun's infrared light.

Goldman's team made samples of gallium arsenide nitride, a highly mismatched alloy that is spiked with nitrogen, which can tap into that underutilized infrared radiation.

The researchers used molecular beam epitaxy to coax the nitrogen to mix with their other elements. Molecular beam epitaxy involves vaporizing pure samples of the mismatched elements and combining them in a vacuum.

Next, the researchers measured the alloy's ability to convert heat into electricity. They wanted to determine whether its 10 parts per million of nitrogen were distributed as individual atoms or as clusters. They found that in some cases, the nitrogen atoms had grouped together, contrary to what the prevailing "band anti-crossing" model predicted.

"We've shown experimentally that the band anti-crossing model is too simple to explain the electronic properties of highly mismatched alloys," Goldman said. "It does not quantitatively explain several of their extraordinary optical and electronic properties. Atomic clusters have a significant impact on the electronic properties of alloy films."

If researchers can learn to control the formation of these clusters, they could build materials that are more efficient at converting light and heat into electricity, Goldman said.

"The availability of higher efficiency thermoelectrics would make it more practical to generate electricity from waste heat such as that produced in power plants and car engines," Goldman said.

This research is newly published online in Physical Review B. The paper is entitled "Nitrogen composition dependence of electron effective mass in gallium arsenide nitride."

This research is funded by the National Science Foundation, the Science Foundation Ireland, and the Center for Solar and Thermal Energy Conversion, an Energy Frontier Research Center funded by the U.S. Department of Energy.


Story Source:

The above story is based on materials provided by University of Michigan. Note: Materials may be edited for content and length.


Journal Reference:

  1. T. Dannecker, Y. Jin, H. Cheng, C. Gorman, J. Buckeridge, C. Uher, S. Fahy, C. Kurdak, R. Goldman. Nitrogen composition dependence of electron effective mass in GaAs_{1−x}N_{x}. Physical Review B, 2010; 82 (12): 125203 DOI: 10.1103/PhysRevB.82.125203

Cite This Page:

University of Michigan. "Forcing mismatched elements together could yield better solar cells." ScienceDaily. ScienceDaily, 8 September 2010. <www.sciencedaily.com/releases/2010/09/100908162942.htm>.
University of Michigan. (2010, September 8). Forcing mismatched elements together could yield better solar cells. ScienceDaily. Retrieved October 22, 2014 from www.sciencedaily.com/releases/2010/09/100908162942.htm
University of Michigan. "Forcing mismatched elements together could yield better solar cells." ScienceDaily. www.sciencedaily.com/releases/2010/09/100908162942.htm (accessed October 22, 2014).

Share This



More Matter & Energy News

Wednesday, October 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Thanks, Marty McFly! Hoverboards Could Be Coming In 2015

Thanks, Marty McFly! Hoverboards Could Be Coming In 2015

Newsy (Oct. 21, 2014) If you've ever watched "Back to the Future Part II" and wanted to get your hands on a hoverboard, well, you might soon be in luck. Video provided by Newsy
Powered by NewsLook.com
Robots to Fly Planes Where Humans Can't

Robots to Fly Planes Where Humans Can't

Reuters - Innovations Video Online (Oct. 21, 2014) Researchers in South Korea are developing a robotic pilot that could potentially replace humans in the cockpit. Unlike drones and autopilot programs which are configured for specific aircraft, the robots' humanoid design will allow it to fly any type of plane with no additional sensors. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Graphene Paint Offers Rust-Free Future

Graphene Paint Offers Rust-Free Future

Reuters - Innovations Video Online (Oct. 21, 2014) British scientists have developed a prototype graphene paint that can make coatings which are resistant to liquids, gases, and chemicals. The team says the paint could have a variety of uses, from stopping ships rusting to keeping food fresher for longer. Jim Drury reports. Video provided by Reuters
Powered by NewsLook.com
China Airlines Swanky New Plane

China Airlines Swanky New Plane

Buzz60 (Oct. 21, 2014) China Airlines debuted their new Boeing 777, and it's more like a swanky hotel bar than an airplane. Enjoy high-tea, a coffee bar, and a full service bar with cocktails and spirits, and lie-flat in your reclining seats. Sean Dowling (@SeanDowlingTV) has the details. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Space & Time

Matter & Energy

Computers & Math

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins