Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanomaterials: Solar express

19.08.2011
A one-pot synthesis provides a simpler and faster route to highly efficient solar cells

Preventing the recombination of free charges produced when light strikes a solar cell is one of the main goal of engineers attempting to extract the maximum energy conversion efficiency from their devices. One way to achieve this is by building into the cell a ‘heterojunction’ between positive (p) and negative (n) type semiconductors, which allows the light-induced positive and negative charge to escape the cell by moving in opposite directions at the heterojunction interface. Mingyong Han at the A*STAR Institute of Materials Research and Engineering and co-workers1 have now discovered a way to produce high-quality nanoscale heterojunctions, setting the stage for cheaper and more efficient photovoltaic devices.

Nanoscale semiconductor crystals provide enhanced surface area for light absorption and are also cheaper to produce than conventional lithography-patterned cell structures. However, it has been extremely difficult to form high-quality heterojunctions between n- and p-type semiconductors in a way that achieves the intimate inter-crystal contact needed to enhance device performance.

Resolving this problem requires a technique that can bind the two semiconductors together chemically. Previous studies have produced binary nanocrystals with a spherical ‘core–shell’ structure. Unfortunately, heterojunction based on these nanocrystals have low energy conversion efficiency because light has difficulty reaching the inner core. Han and his co-workers overcame this problem by adopting a different route for synthesis.

First, the researchers used a blend of surfactants under hot thermal conditions to produce copper(I) sulfide (CuxS), a well-known p-type semiconductor, in distinctively shaped hexagonal disks roughly 40 nanometers wide and 15 nanometers thick. The well-defined facets of these novel materials enabled the researchers to nucleate the crystallization of n-type cadmium sulfide (CdS) onto the outer edges of the crystals.

Next, through a process known as cation exchange, the researchers persuaded the n-type crystals to grow inward, effectively chemically converting a portion of the CuxS disks into CdS. “This method results in nano-heterostructures with the same morphology as the original material,” says Han. By carefully optimizing the reaction conditions, the researchers transformed the hexagonal nanodisk into a perfectly symmetric, side-by-side heterojunction. Zinc metals were also incorporated into the interface to further tweak its electrical performance.

Han notes that the CuxS–CdS heterostructure is promising for solar cell technology because of its dually accessible surface and an energy band alignment that drives strong charge separation. The team also expects to synthesize a wide range of new semiconductor pairs with this one-pot technique, taking advantage of the system’s extraordinary crystallization properties.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering

References

Regulacio, M. D. et al. One-pot synthesis of Cu1.94S–CdS and Cu1.94S–ZnxCd1–xS nanodisc heterostructures. Journal of the American Chemical Society 133, 2052–2055 (2011).

Eugene Low | Research asia research news
Further information:
http://www.imre.a-star.edu.sg/
http://www.researchsea.com

More articles from Materials Sciences:

nachricht The stacked colour sensor
16.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

nachricht Counterfeits and product piracy can be prevented by security features, such as printed 3-D microstructures
16.11.2017 | Karlsruher Institut für Technologie (KIT)

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>