Major leap towards graphene for solar cells

Surprising result: Graphene retains its properties even when coated with silicon

2013-10-08

(Press-News.org) Graphene has extreme conductivity and is completely transparent while being inexpensive and nontoxic. This makes it a perfect candidate material for transparent contact layers for use in solar cells to conduct electricity without reducing the amount of incoming light - at least in theory. Whether or not this holds true in a real world setting is questionable as there is no such thing as "ideal" graphene - a free floating, flat honeycomb structure consisting of a single layer of carbon atoms: interactions with adjacent layers can change graphene's properties dramatically.

"We examined how graphene's conductive properties change if it is incorporated into a stack of layers similar to a silicon based thin film solar cell and were surprised to find that these properties actually change very little," Marc Gluba explains. To this end, they grew graphene on a thin copper sheet, next transferred it to a glass substrate, and finally coated it with a thin film of silicon. They examined two different versions that are commonly used in conventional silicon thin-film technologies: one sample contained an amorphous silicon layer, in which the silicon atoms are in a disordered state similar to a hardened molten glas; the other sample contained poly-crystalline silicon to help them observe the effects of a standard crystallization process on graphene's properties.

Even though the morphology of the top layer changed completely as a result of being heated to a temperature of several hundred degrees C, the graphene is still detectable. "That's something we didn't expect to find, but our results demonstrate that graphene remains graphene even if it is coated with silicon," says Norbert Nickel.

Their measurements of carrier mobility using the Hall-effect showed that the mobility of charge carriers within the embedded graphene layer is roughly 30 times greater than that of conventional zinc oxide based contact layers. Says Gluba: "Admittedly, it's been a real challenge connecting this thin contact layer, which is but one atomic layer thick, to external contacts. We're still having to work on that." Adds Nickel: "Our thin film technology colleagues are already pricking up their ears and wanting to incorporate it." The researchers obtained their measurements on one square centimeter samples, although in practice it is feasible to coat much larger areas than that with graphene.

INFORMATION:

This work was recently published in Applied Physics Letters Vol. 103, 073102 (2013).

Authors: M. A. Gluba, D. Amkreutz, G. V. Troppenz, J. Rappich, and N. H. Nickel

doi: 10.1063/1.4818461

ELSE PRESS RELEASES FROM THIS DATE:

First ever evidence of a comet striking Earth

2013-10-08

The first ever evidence of a comet entering Earth's atmosphere and exploding, raining down a shock wave of fire which obliterated every life form in its path, has been discovered by a team of South African scientists and international collaborators. The discovery has not only provided the first definitive proof of a comet striking Earth, millions of years ago, but it could also help us to unlock, in the future, the secrets of the formation of our solar system. "Comets always visit our skies – they're these dirty snowballs of ice mixed with dust – but never before in ...

Study shows snacking on almonds decreased appetite without increasing body weight

2013-10-08

MODESTO, Calif., Oct. 8, 2013 -- A new study published in the October issue of the European Journal of Clinical Nutrition found that study participants eating 1.5 ounces of dry-roasted, lightly salted almonds every day experienced reduced hunger and improved dietary vitamin E and monounsaturated ("good") fat intake without increasing body weight.[i] Snacking has become nearly universal behavior in the United States, with an estimated 97% of Americans consuming at least one snack per day.[ii] In light of increasing snacking frequency[ii] and snack size[iii] among U.S. ...

Studying the social side of carnivores

2013-10-08

EAST LANSING, Mich. — The part of the brain that makes humans and primates social creatures may play a similar role in carnivores, according to a growing body of research by a Michigan State University neuroscientist. In studying spotted hyenas, lions and, most recently, the raccoon family, Sharleen Sakai has found a correlation between the size of the animals' frontal cortex and their social nature. In her latest study, Sakai examined the digitally recreated brains of three species in the Procyonid family – the raccoon, the coatimundi and the kinkajou – and found the ...

A potential new strategy to face dementia

2013-10-08

Ancona, Italy, 8 October 2013 – Alzheimer's disease (AD) affects millions of people worldwide. As a result of an increase in life expectancy, the number of patients with dementia is expected to increase dramatically. Due to the lack of effective treatments that can slow down or reverse the progression of AD, preventive measures to lower the prevalence rate of AD by means of managing potential or actual risk factors is a reasonable clinical strategy. In this respect, identifying treatable factors which are able to promote cognitive deterioration would have important practical ...

No viral cause for breast cancer and brain tumors

2013-10-08

A major study conducted at the Sahlgrenska Academy has now disproved theories of a viral cause for breast cancer and the brain tumour, glioblastoma. The study, which was based on over seven billion DNA sequences and which is published in Nature Communications, found no genetic traces of viruses in these forms of cancer. It has been scientifically proven that about 15 per cent of all cancer cases are the result of viral infection, but many researchers believe that even more cancers could be caused by viruses. Among other theories, it is suggested that the Epstein-Barr ...

Something in the (expecting mother's) water

2013-10-08

Pregnant women living in areas with contaminated drinking water may be more likely to have babies that are premature or with low birth weights (considered less than 5.5 pounds), according to a study based at Princeton University's Woodrow Wilson School of Public and International Affairs. Featured in the Canadian Journal of Economics, the study shows that the effects of contaminated water—which include numerous cognitive and developmental impairments—are particularly significant for babies born to less-educated mothers. These mothers also are less likely to uproot from ...

Solving the internet capacity crunch

2013-10-08

With optical fibre networks gradually approaching their theoretical capacity limits, new types of fibres such as multicore fibres have been at the focus of worldwide research to overcome critical capacity barriers, which threaten the evolution of the Internet. The University of Bristol in collaboration with the National Institute of Information and Communications Technology (NICT) have demonstrated successfully for the first time a multicore fibre-based network, which will form the foundation for the future Internet infrastructure. The research relies on Space Division ...

Non-specific and specific RNA binding proteins found to be fundamentally similar

2013-10-08

Researchers from Case Western Reserve University School of Medicine have found unexpected similarities between proteins that were thought to be fundamentally different. The team studied how proteins bind to RNA, a process required for gene expression. It is known that some proteins only bind RNAs with certain sequences. Other proteins have been deemed "non-specific" because they interact with RNAs at seemingly random places. But the Case Western Reserve team has published a new study in Nature showing that non-specific proteins actually do have the ability to be specific ...

AGU journal highlights -- Oct. 8 2013

2013-10-08

The following highlights summarize research papers that have been recently published in Journal of Geophysical Research-Atmospheres (JGR-D), Journal of Geophysical Research-Earth Surface (JGR-F), Journal of Geophysical Research-Oceans (JGR-C), Geophysical Research Letters, and Paleoceanography. In this release: 1. Measuring global sulfur dioxide emissions with satellite sensors 2. Seismic network detects landslides on broad area scale 3. Examining increasing potential for storms with global warming 4. Understanding oxygen depletion on the Oregon coastal shelf 5. ...

Everything in moderation: Excessive nerve cell pruning leads to disease

2013-10-08

Scientists at the Montreal Neurological Institute and Hospital-The Neuro, McGill University, have made important discoveries about a cellular process that occurs during normal brain development and may play an important role in neurodegenerative diseases. The study's findings, published in Cell Reports, a leading scientific journal, point to new pathways and targets for novel therapies for Alzheimer's, Parkinson's, ALS and other neurodegenerative diseases that affect millions of people world-wide. Research into neurodegenerative disease has traditionally concentrated ...

LAST 30 PRESS RELEASES:

Increasing the number of coronary interventions in patients with acute myocardial infarction does not appear to reduce death rates

Striking genomic architecture discovered in embryonic reproductive cells before they start developing into sperm and eggs

AABNet and partners launch landmark guide on the conservation of African livestock genetic resources and sustainable breeding strategies

Produce hydrogen and oxygen simultaneously from a single atom! Achieve carbon neutrality with an 'All-in-one' single-atom water electrolysis catalyst

Sleep loss linked to higher atrial fibrillation risk in working-age adults

Visible light-driven deracemization of α-aryl ketones synergistically catalyzed by thiophenols and chiral phosphoric acid

Babies with an increased likelihood of autism may struggle to settle into deep, restorative sleep, according to a new study from the University of East Anglia.