PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Watching solar cells grow

2013-06-27
(Press-News.org) This news release is available in German.

Their results show during which process stages the growth can be accelerated and when additional time is required to reduce defects. Their work has now been published online in Advanced Energy Materials.

Today's chalcopyrite thin film cells based on copper indium gallium selenide are already reaching efficiencies of more than 20 percent. For the fabrication of the extremely thin polycrystalline layers, the process of coevaporation has lead to the best results so far: During coevaporation, two separate elements are evaporated simultaneously, first indium (or gallium) and selenium, then copper and selenium, and, finally, indium (or gallium) and selenium again. This way, a thin film of crystals forms, which exhibit only a small number of defects. "Until recently, we did not fully understand what exactly happens during this coevaporation process," says Dr. Roland Mainz of the HZB's Institute of Technology. The team of physicists worked for three years using on-site and real-time measurements to find an answer to this question.

Novel experimental chamber constructed

For these measurements they constructed a new kind of experimental chamber, which allows for an analysis of polycrystalline chalcopyrite film formation during coevaporation when exposed to synchrotron light at BESSY II. In addition to the evaporation sources for the elements, this vacuum chamber contains heating and cooling elements to control the evaporative process. According to Mainz, "one of the main challenges was adjusting the chamber, which weighs around 250 kilograms, with an accuracy of 10 micrometer." Because of thermal expansion during evaporation, the height has to be automatically re-adjusted every few seconds.

Combination of x-ray diffraction and fluorescence analysis

With this setup, for the first time worldwide they were able to observe polycrystalline film growth using in situ X-ray diffraction and fluorescence analysis during coevaporation in real time. "We are now able to see how crystalline phases form and transform and when defects form during the different stages of evaporation. "But we're also able to tell when these defects disappear again." This takes place in the second process stage, when copper and selenium are evaporated. Excess copper, which deposits at the surface in the form of copper selenide helps to remove defects. "This was already known before from previous experiments. But now, using fluorescence signals and numeric model calculations, we are able to show how copper selenide penetrates the copper indium selenide layer," Mainz explains. Here clear-cut differences between copper indium selenide and copper gallium selenide layers became apparent: While copper is able to penetrate the copper-indium-selenide layer, in the case of copper-gallium-selenide, which is otherwise pretty similar, it remains at the surface. This could be one possible reason for why the use of pure copper gallium selenide does not yield high efficiency solar cells.

Concrete steps for optimization

"We now know that for further optimization of the process it is important to concentrate on the transition point into the copper-rich phase. Up to now the process was performed very slowly throughout all stages to give defects enough time to disappear. Our findings suggest that the process can be accelerated at some stages and that it is sufficient to slow it down only at points where defects are efficiently eliminated," explains Mainz. Mainz is already looking forward to future project EMIL, which is currently being set up at BESSY II. Here even more powerful tools will become available for the study of complex processes during growth of new types of solar cells in situ and in real time.



INFORMATION:



ELSE PRESS RELEASES FROM THIS DATE:

Dynamic interplay of ecology, infectious disease, and human life

2013-06-27
Two symposia focusing on the ecological dynamics of infectious diseases such as avian influenza, Yellow Fever, and Lyme will take place during the Ecological Society of America's 98th Annual Meeting, held this year in Minneapolis, Minnesota. One will look at human influences on viral and bacterial diseases through our alteration of landscapes and ecological processes, while the other will focus on the emerging field of eco-epidemiology that seeks to integrate biomedical and ecological research approaches to address human health threats. The symposium on Monday, August ...

Sea lampreys turning up the heat

2013-06-27
Male sea lampreys may not be the best-looking creatures swimming in our lakes and streams, but they apparently have something going for them that the ladies may find irresistible. Research by a team of Michigan State University scientists found that the males have a secondary sex characteristic that creates heat when they get near a female lamprey, something the females find hard to say no to. The work of the team focused on a small bump located near the male's anterior dorsal fin. Close examination of this bump determined that it was full of fat cells, cells that are ...

Pneumonia revealed in a cough

2013-06-27
A new method, which analyzes the sounds in a child's cough, could soon be used in poor, remote regions to diagnose childhood pneumonia reliably. According to Udantha Abeyratne from the University of Queensland in Australia and colleagues, this simple technique of recording coughs with a microphone on the patient's bedside table, has the potential to revolutionize the management of childhood pneumonia in remote regions around the world. Their work¹ is published online in Springer's journal Annals of Biomedical Engineering². Pneumonia is the leading killer of young children ...

A telescope for the eye: New contacts may improve sight for macular degeneration patients

2013-06-27
WASHINGTON, June 27, 2013—Contact lenses correct many people's eyesight but do nothing to improve the blurry vision of those suffering from age-related macular degeneration (AMD), the leading cause of blindness among older adults in the western world. That's because simply correcting the eye's focus cannot restore the central vision lost from a retina damaged by AMD. Now a team of researchers from the United States and Switzerland led by University of California San Diego Professor Joseph Ford has created a slim, telescopic contact lens that can switch between normal and ...

Breaking habits before they start

2013-06-27
CAMBRIDGE, MA -- Our daily routines can become so ingrained that we perform them automatically, such as taking the same route to work every day. Some behaviors, such as smoking or biting your fingernails, become so habitual that we can't stop even if we want to. Although breaking habits can be hard, MIT neuroscientists have now shown that they can prevent them from taking root in the first place, in rats learning to run a maze to earn a reward. The researchers first demonstrated that activity in two distinct brain regions is necessary in order for habits to crystallize. ...

APS issues statement on NIH implementation of recommendations for chimpanzee research

2013-06-27
Bethesda, Md. -- The American Physiological Society (APS) issued the following statement today in response to the announcement on the use of chimpanzees in medical research: "The American Physiological Society looks forward to a careful review of Dr. Collins' decision regarding NIH's implementation of the IOM principles and criteria. The APS previously offered comments on the Working Group report. We are hopeful that Dr. Collins has taken into account our concerns, which include implementing flexible, outcome-oriented guidelines for chimpanzee housing and social groups; ...

Chemists work to desalt the ocean for drinking water, 1 nanoliter at a time

2013-06-27
AUSTIN, Texas – By creating a small electrical field that removes salts from seawater, chemists at The University of Texas at Austin and the University of Marburg in Germany have introduced a new method for the desalination of seawater that consumes less energy and is dramatically simpler than conventional techniques. The new method requires so little energy that it can run on a store-bought battery. The process evades the problems confronting current desalination methods by eliminating the need for a membrane and by separating salt from water at a microscale. The technique, ...

Food contaminants worsen metabolic problems in obese mice

2013-06-27
In order to get a better understanding of these effects, researchers from the Inserm cardiovascular, metabolism, diabetology and nutrition unit (U1060 « Laboratoire de recherche en cardiovasculaire, métabolisme, diabétologie et nutrition » Inserm/Inra/Université Lyon 1) introduced a "cocktail" of contaminants mixed with low doses of dioxin, PCB, bisphenol A and phtalates into the feeding of mice that had already been rendered obese by a high-fat diet. The results show that metabolic changes occur in these mice, but that the effects differ depending on the gender. Females ...

Seniors are not just wrinkly adults

2013-06-27
WASHINGTON — Emergency patients over the age of 74 have significantly different and more complex health and social needs than their younger counterparts, even after controlling for illness severity, which has important implications about aging populations and emergency departments of the future. The results of the most extensive international study of the characteristics and outcomes of older emergency patients to be reported to date were published online Tuesday in Annals of Emergency Medicine ("Profiles of Older Patients in the Emergency Department: Findings from the ...

Making hydrogenation greener

2013-06-27
Researchers from McGill University, RIKEN (The Institute of Physical and Chemical Research, Wako, Japan) and the Institute for Molecular Science (Okazaki, Japan) have discovered a way to make the widely used chemical process of hydrogenation more environmentally friendly – and less expensive. Hydrogenation is a chemical process used in a wide range of industrial applications, from food products, such as margarine, to petrochemicals and pharmaceuticals. The process typically involves the use of heavy metals, such as palladium or platinum, to catalyze the chemical reaction. ...

LAST 30 PRESS RELEASES:

Fat may play an important role in brain metabolism

New study finds no lasting impact of pandemic pet ownership on human well-being

New insights on genetic damage of some chemotherapies could guide future treatments with less harmful side effects

Gut microbes could protect us from toxic ‘forever chemicals’

Novel modelling links sea ice loss to Antarctic ice shelf calving events

Scientists can tell how fast you're aging from a single brain scan

U.S. uterine cancer incidence and mortality rates expected to significantly increase by 2050

Public take the lead in discovery of new exploding star

What are they vaping? Study reveals alarming surge in adolescent vaping of THC, CBD, and synthetic cannabinoids

ECMWF - delivering forecasts over 10 times faster and cutting energy usage by 1000

Brazilian neuroscientist reveals how viral infections transform the brain through microscopic detective work

Turning social fragmentation into action through discovering relatedness

Cheese may really be giving you nightmares, scientists find

Study reveals most common medical emergencies in schools

Breathable yet protective: Next-gen medical textiles with micro/nano networks

Frequency-engineered MXene supercapacitors enable efficient pulse charging in TENG–SC hybrid systems

Developed an AI-based classification system for facial pigmented lesions

Achieving 20% efficiency in halogen-free organic solar cells via isomeric additive-mediated sequential processing

New book Terraglossia reclaims language, Country and culture

The most effective diabetes drugs don't reach enough patients yet

Breast cancer risk in younger women may be influenced by hormone therapy

Strategies for staying smoke-free after rehab

Commentary questions the potential benefit of levothyroxine treatment of mild hypothyroidism during pregnancy

Study projects over 14 million preventable deaths by 2030 if USAID defunding continues

New study reveals 33% gap in transplant access for UK’s poorest children

Dysregulated epigenetic memory in early embryos offers new clues to the inheritance of polycystic ovary syndrome (PCOS)

IVF and IUI pregnancy rates remain stable across Europe, despite an increasing uptake of single embryo transfer

It takes a village: Chimpanzee babies do better when their moms have social connections

From lab to market: how renewable polymers could transform medicine

Striking increase in obesity observed among youth between 2011 and 2023

[Press-News.org] Watching solar cells grow