Charge transport in hybrid silicon solar cells
2015-08-17
(Press-News.org) This news release is available in German.
Their results have now been published in the Nature journal Scientific Reports (doi:10.1038/srep13008) and could point the way toward improvements in hybrid solar cells.
The system they investigated is based on conventional n-type silicon wafers coated with the highly conductive polymer mixture PEDOT:PSS and displays a power conversion efficiency of about 14 %. This combination of materials is currently extensively investigated by many teams in the research community.
"We systematically surveyed the characteristic curves, the dark current as well as the capacitance of such devices using silicon wafers with different doping concentrations" explains Sara Jäckle, lead author of the article and Ph.D. student in Prof. Silke Christiansen's team (HZB Institute of Nano-architectures for Energy Conversion and research group leader at the Max Planck Institute for the Science of Light MPL in Erlangen). "We learned that the characteristic curves in the dark as well as the open-circuit voltage of the solar cells are dependent on the doping concentration of the silicon wafer. This behaviour and the order of magnitude of the measured values do not correspond at all to those of a typical Schottky junction."
The result is surprising because the n-type silicon is a typical semiconductor, while PEDOT:PSS is usually described as a metallic conductor. Up to now it has therefore been assumed that a typical metal-semiconductor junction would exist between these two materials, one that can be described by the Schottky equation.
Supported by measurements also in collaboration with the research team of Prof. Klaus Lips (Energy Materials In-Situ Laboratory Berlin (EMIL), Institute for Nanospectroscopy) the data and a comparison with theoretical models demonstrate otherwise. In a junction with n-type silicon, the conductive organic layer behaves like a p-type semiconductor rather than a metal. "The data shows a dependence on the degree of doping in the n-material just like a heterojunction between a p- and n-type semiconductors does", says Sara Jäckle.
"This work deals with a very important aspect of these kinds of hybrid systems, namely the behaviour at the interface", says Silke Christiansen. "The results are probably also valid for other hybrid systems, important for photovoltaics or other optoelectronic applications such as perovskite solar cells. They suggest new ways for optimising devices by tuning the interface properties".
INFORMATION:
Note: The Collaborative Research Centre (SFB 951) Hybrid Inorganic/Organic Systems for Opto-Electronics (HIOS) has just entered its second funding period. Prof. Christiansen and her team will be continuing their research on hybrid interfaces and devices in a subproject of this SFB.
[Attachments] See images for this press release:
ELSE PRESS RELEASES FROM THIS DATE:
2015-08-17
Millions of tons of road salt are applied to streets and highways across the United States each winter to melt ice and snow and make travel safer, but the effects of salt on wildlife are poorly understood.
A new study by biologists from Case Western Reserve University suggests exposure to road salt, as it runs off into ponds and wetlands where it can concentrate--especially during March and early April, when frogs are breeding--may increase the size of wood frogs, but also shorten their lives.
Wood frog tadpoles exposed to road salt grew larger and turned into ...
2015-08-17
In addition to melting icecaps and imperiled wildlife, a significant concern among scientists is that higher Arctic temperatures brought about by climate change could result in the release of massive amounts of carbon locked in the region's frozen soil in the form of carbon dioxide and methane. Arctic permafrost is estimated to contain about a trillion tons of carbon, which would potentially accelerate global warming. Carbon emissions in the form of methane have been of particular concern because on a 100-year scale methane is about 25-times more potent than carbon dioxide ...
2015-08-17
Magnetism in nanoscale layers only a few tens of atoms thick is one of the foundations of the big data revolution - for example, all the information we download from the internet is stored magnetically on hard disks in server farms dotted across the World. Recent work by a team of scientists working in Singapore, The Netherlands, USA and Ireland, published on 14 August 2015 in the prestigious journal, Science, has uncovered a new twist to the story of thin-film magnetism.
The team from the National University of Singapore (NUS) - Mr Li Changjian, a graduate student from ...
2015-08-17
Bilingual children pose unique challenges for clinicians, and, until recently, there was little research on young bilinguals to guide clinical practice. In the past decade, however, research on bilingual development has burgeoned, and the scientific literature now supports several conclusions that should help clinicians as they assess bilingual children and advise their parents.
In an article recently published in Seminars in Speech and Language, Erika Hoff, Ph.D., a professor of psychology in the Charles E. Schmidt College of Science at Florida Atlantic University, ...
2015-08-17
ANN ARBOR, Mich. - One of the most common complaints about hospitals is the noise. Patients complain that they can't sleep soundly in the environment of multiple monitors, paging systems, wheelchairs and gurneys, and carts that squeak.
Ongoing efforts at the University of Michigan Health System are making the hospital quieter, and the hospital has tested sound panels designed to dial down noise.
During a pilot study, strategically placed sound acoustic panels helped diffuse sound in the hallways around patient rooms. The modest 3-4 sound decibel drop is recognizable ...
2015-08-17
When researchers dream about electronics of the future, they more or less dream of pouring liquids into a beaker, stirring them together and decanting a computer out onto the table. This field of research is known as self-assembling molecular electronics. But, getting chemical substances to self-assemble into electronic components is just as complicated as it sounds. Now, a group of researchers has published their breakthrough within the field. The group consists of first-year nanoscience students from the University of Copenhagen.
Thomas Just Sørensen, an associate ...
2015-08-17
This news release is available in German. Two growth-promoting groups of substances, or phytohormones, the gibberellins and the brassinosteroids, are used independently of each other for the breeding and production of crop plants. A team of scientists at Technical University of Munich (TUM) has now discovered that the two act in concert - without brassinosteroids, a plant is unable to produce gibberellins.
For their current investigations, a research group at the Technical University of Munich, supported by scientists from the Helmholtz Zentrum Munich and the TU Braunschweig ...
2015-08-17
ANN ARBOR, Mich. -- With every breath you take, microbes have a chance of making it into your lungs. But what happens when they get there? And why do dangerous lung infections like pneumonia happen in some people, but not others?
Researchers at the University of Michigan Medical School have started to answer these questions by studying the microbiome of the lungs - the community of microscopic organisms are in constant contact with our respiratory system.
By studying these bacterial communities, and how they change in illness, they hope to pave the way for new ways ...
2015-08-17
Troubling questions about multiracial congregations' potential to address racial inequality are raised by a new national study done by researchers at Baylor University, the University of Southern California and the University of Chicago.
The study -- "United by Faith? Race/Ethnicity, Congregational Diversity, and Explanations of Racial Inequality" -- is published in the journal Sociology of Religion.
"We find little evidence that multiracial congregations promote progressive racial views among attendees of any race or ethnicity," the researchers wrote. Views of minorities ...
2015-08-17
BOSTON, Aug. 17, 2015 --Native North Americans have long adorned themselves and their homes with fragrant sweetgrass (Hierochloe odorata), a native plant used in traditional medicine, to repel biting insects, and mosquitoes in particular. Now, researchers report that they have identified the compounds in sweetgrass that keep these bugs at bay.
The team will describe their approach in one of more than 9,000 presentations at the 250th National Meeting & Exposition of the American Chemical Society (ACS), the world's largest scientific society, taking place here through Thursday.
Mosquitoes ...
LAST 30 PRESS RELEASES:
[Press-News.org] Charge transport in hybrid silicon solar cells
