Featured Research

from universities, journals, and other organizations

Solar energy: A richer harvest on the horizon

Date:
August 31, 2013
Source:
The Agency for Science, Technology and Research (A*STAR)
Summary:
Theoretical simulations reveal that layered semiconductors with magnetic interfaces are potent catalysts for solar energy capture and conversion.

Semiconductor nanostructures are poised to play a big role in future solar-powered hydrogen generation systems, according to a new study by researchers at the A*STAR Institute of High Performance Computing1. Hui Pan and Yong-Wei Zhang report that model interfaces made from gallium nitride (GaN) and zinc oxide (ZnO) semiconductors have tunable magnetic and light-harvesting capabilities -- factors that can greatly improve the photocatalytic transformation of water into hydrogen fuel.

Most photoelectrochemical cells use titanium dioxide electrodes to absorb light and split water molecules into hydrogen and oxygen gas. But because this mineral has a large bandgap -- a measure of energy needed to initiate photoreactions -- these devices respond only to a tiny fraction of the solar spectrum. A promising way to boost this efficiency is with 'superlattice' materials that stack two different semiconductors into alternate, nanometer-thin layers. The two-dimensional channels that emerge from superlattices resemble conductive nanowires for swift charge-carrier movement. Bandgaps in these hetero-nanostructures have a demonstrated dependence on semiconductor composition and layer thickness.

Pan and Zhang investigated superlattices based on stacked GaN and ZnO layers, two semiconductors with similar electronic and structural properties that are widely used in optoelectronic devices. Using density functional theory calculations, they optimized a periodic GaN-ZnO model superlattice (see image). These computations, which describe the charge and electron spin states of materials, showed that the two semiconductor layers formed crystalline nanowire arrangements with no magnetic characteristics.

The duo then systematically introduced small defects -- atomic substitutions that slightly disrupt semiconductor crystallinity -- into the GaN-ZnO superlattice. To Pan and Zhang's surprise, they observed significant magnetism at several types of defect interface. According to Pan, this extraordinary activity is due to 'polar discontinuities' that form when positively charged defects partially neutralize negative charges at Ga-O interface points. Unpaired electrons then accumulate around Zn-N connections and generate magnetic forces that can boost charge separation and mobility during the reaction known as photocatalysis.

The researchers also found that engineered polar discontinuities could significantly alter semiconductor bandgaps by generating intermediate energy levels. These zones act as 'stepping stones' that make it easier for photons, or light-transmitting particles, to excite electrons for water-splitting reactions. Pan notes that once these intriguing properties of GaN-ZnO nanostructures are verified through laboratory studies, the materials may find application in energy-harvesting solar cells. "If this design proves efficient in both theory and experiment, we would then look for commercial applications by collaborating with industry," he says.


Story Source:

The above story is based on materials provided by The Agency for Science, Technology and Research (A*STAR). Note: Materials may be edited for content and length.


Journal Reference:

  1. Hui Pan, Yong-Wei Zhang. GaN/ZnO superlattice nanowires as photocatalyst for hydrogen generation: A first-principles study on electronic and magnetic properties. Nano Energy, 2012; 1 (3): 488 DOI: 10.1016/j.nanoen.2012.03.001

Cite This Page:

The Agency for Science, Technology and Research (A*STAR). "Solar energy: A richer harvest on the horizon." ScienceDaily. ScienceDaily, 31 August 2013. <www.sciencedaily.com/releases/2013/08/130831110639.htm>.
The Agency for Science, Technology and Research (A*STAR). (2013, August 31). Solar energy: A richer harvest on the horizon. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/2013/08/130831110639.htm
The Agency for Science, Technology and Research (A*STAR). "Solar energy: A richer harvest on the horizon." ScienceDaily. www.sciencedaily.com/releases/2013/08/130831110639.htm (accessed July 25, 2014).

Share This




More Earth & Climate News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Goma Cheese Brings Whiff of New Hope to DRC

Goma Cheese Brings Whiff of New Hope to DRC

Reuters - Business Video Online (July 24, 2014) The eastern region of the Democratic Republic of Congo, mainly known for conflict and instability, is an unlikely place for the production of fine cheese. But a farm in the village of Masisi, in North Kivu is slowly transforming perceptions of the area. Known simply as Goma cheese, the Congolese version of Dutch gouda has gained popularity through out the region. Ciara Sutton reports. Video provided by Reuters
Powered by NewsLook.com
Bill Gates: Health, Agriculture Key to Africa's Development

Bill Gates: Health, Agriculture Key to Africa's Development

AFP (July 24, 2014) Health and agriculture development are key if African countries are to overcome poverty and grow, US software billionaire Bill Gates said Thursday, as he received an honourary degree in Ethiopia. Duration: 00:36 Video provided by AFP
Powered by NewsLook.com
Higgins Breaks Record at Mt. Washington

Higgins Breaks Record at Mt. Washington

Driving Sports (July 24, 2014) Subaru Rally Team USA drivers David Higgins and Travis Pastrana face off against a global contingent of racers at the annual Mt. Washington Hillclimb in New Hampshire. Includes exclusive in-car footage from Higgins' record attempt. Video provided by Driving Sports
Powered by NewsLook.com
Storm Kills Three, Injures 20 at Virginia Campground

Storm Kills Three, Injures 20 at Virginia Campground

Reuters - US Online Video (July 24, 2014) A likely tornado tears through an eastern Virginia campground, killing three and injuring at least 20. Linda So reports. Video provided by Reuters
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:
from the past week

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