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 September 19, 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 September 19, 2014).

Share This



More Earth & Climate News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Wildfires in CA Burn Forest Asunder

Raw: Wildfires in CA Burn Forest Asunder

AP (Sep. 18, 2014) An out-of-control Northern California wildfire has nearly 2,800 people from their homes as it continues to grow, authorities said Thursday. Authorities said a man has been arrested on suspicion of arson for starting the fire on Saturday. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) Video provided by AP
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