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Iranian academic researchers produced nanocomposites which can be used in the recovery of bone and damaged tissues.
Iranian researchers succeeded in the production of nanoparticles with new structures and special magnetic properties.
LaVison BioTec, developers of advanced microscopy solutions for the life sciences, announce they will introduce new products for their UltraMicroscope and TriM Scope microscopy products at the 2014 an...
Associate Professor Ki-Bum Lee has developed patent-pending technology that may overcome one of the critical barriers to harnessing the full therapeutic potential of stem cells.
Bio-Inspired Bleeding Control: Taking a cue from the human bodys own coagulation processes, researchers at UC Santa Barbara synthesize platelet-like nanoparticles that can do more than clot blood - See more at: http://www.news.ucsb.edu/2014/014506/bio-in
Stanching the free flow of blood from an injury remains a holy grail of clinical medicine. Controlling blood flow is a primary concern and first line of defense for patients and medical staff in many...
Leti Will Present 17 Papers at 2014 IEDM; the Highest-ever Total Includes Four Invited Papers: Institute also Will Present its Latest Results in Key Technologies and Its Roadmap for Silicon Nano-technologies at Workshop
CEA-Leti will present 17 papers at the 2014 IEEE International Electron Devices Meeting (IEDM) Dec. 15-17 in San Francisco, Calif. The total is the most ever for Leti and it includes four invited pape...
Iranian researchers from Amirkabir University of Technology presented a mathematical model to predict vibrating behavior of conical shell's nanocomposite objects.
SUNY Poly Student Awarded Fellowship with the U.S. Department of Energy's Postgraduate Research Program: Ph.D. Candidate Accepts Postmaster's Appointment To Conduct Research At Albany NanoTech Complex
As testament to Governor Andrew M. Cuomo's leadership and support of New York's innovation-education model, SUNY Polytechnic Institute today announced research student Gnanaprakash Dharmalingam has ac...
"Surface Energy-Assisted Perfect Transfer of Centimeter-Scale Monolayer and Fewlayer MoS2 Films onto Arbitrary Substrates" Authors: Alper Gurarslan, Yifei Yu, Yiling Yu, Francisco Suarez, Shanshan...
Functional Nanocoatings For Filtration Media Presented By Europlasma At Filtration 2014: Visit Europlasma booth 624 at Filtration 2014, Baltimore, November 19th and 20th
Belgium based Europlasma, a global leader in low pressure plasma technology, is pleased to present, during Filtration 2014, its family of innovative nanocoatings for the filtration industry under the...
New technique could sequence DNA.
Northwestern researchers have designed new types of artificially structured optical materials thanks to an algorithm based on Darwinian evolutionary principles.
In recent years, polymer solar cells have drawn considerable research interest due to their attractive features including flexibility, semi-transparency, and manufacturability using cost-effective continuous printing processes (read more: "The state of nanoimprinted polymer organic solar cell technology (http://www.nanowerk.com/spotlight/spotid=28622.php)"). However, one challenge limiting their commercialization is the relatively low power conversion efficiency when compared to inorganic solar cells."One of the causes for polymer solar cells' low performance is the difficulty to simultaneously realize donor-acceptor phase separation within the short exciton diffusion length (∼10 nm) and high charge mobility, especially hole mobility, which are critical for charge separation and transport," Yi Yang, a senior engineer at Globalfoundries, tells Nanowerk. "So far it has been impossible to achieve such a morphology in the most widely used bulk heterojunction structure in which randomly distributed phases cause significant charge recombination." New work, led by Walter Hu (http://www.ee.utdallas.edu/people/facultypages/Hu.html), an Associate Professor of Electrical Engineering, and Anvar Zakhidov (http://nanotech.utdallas.edu/personnel/staff/zakhidov.html), a professor of physics, both at UT Dallas, shows that nanoimprint lithography (NIL) is an effective technique to solve these issues simultaneously. The results, recently published in ACS Applied Materials Interfaces ("Efficient Low Bandgap Polymer Solar Cell with Ordered Heterojunction Defined by Nanoimprint Lithography" (http://dx.doi.org/doi:10.1021/am505303a)), show that low bandgap polymer solar cells with high efficiency of 5.5% can be fabricated using NIL. "Taking into account the fact that low bandgap polymers are becoming the main stream for this type of solar cell, we believe this technique will increasingly find more applications," says Yang. In a previous study ("How nanostructure geometry affects polymer photovoltaic device efficiency (http://www.nanowerk.com/spotlight/spotid=36631.php)"), the researchers focused on nanoimprinted P3HT solar cells. After carefully optimizing the nanostructure geometry, they achieved an efficiency of 3-4%, which is not as high as the efficiency record (over 4%) other groups have achieved with this polymer. In the new study, they extended their technique to low bandgap polymer solar cells and realized a high efficiency up to 5.5%, which is among the best efficiencies for this polymer reported in the literature. This result indicates that nanoimprint fabrication works better for low bandgap polymer solar cells. In the new work, the team demonstrates the feasibility of using nanoimprint lithography to make efficient low bandgap polymer solar cells with well-ordered heterojunction. They fabricate high-quality low bandgap conjugated polymer (PCPDTBT) nanogratings using this technique for the first time. "We found that NIL makes PCPDTBT chains interact more strongly and form an improved structural ordering," says Yang. "Solar cells made with the highest aspect ratio PCPDTBT nanostructures show a high power conversion efficiency of 5.5%. They are the most efficient nanoimprinted polymer solar cells, as well as the best reported solar cells using the same material." Nanoimprint lithography has emerged as an effective fabrication technique to precisely define the nanomorphology in polymer solar cells. Controlled chain ordering as well as a bicontinuous and interdigitized heterojunction can be achieved by imprinting conjugated polymers, where a nanoimprint induced chain alignment is present, followed by infiltrating fullerene into patterned polymer nanostructures. However, as Yang notes, most studies so far have focused on nanoimprinted P3HT/fullerene solar cells. "This material combination is not ideal due to a mismatch between the absorption of P3HT and solar spectrum, which has a maximum photon flux at 1.6-1.8 eV while P3HT has a relatively large bandgap of 1.9-2.0 eV," he explains. "A bandgap of 1.3-1.5 eV is considered to be ideal for polymer-fullerene solar cells." In recent years, many low bandgap polymers have been synthesized with record-breaking efficiencies. However, as Yang points out, it has been proven that the donor and acceptor phase separation for these polymers cannot be realized by thermal or solvent vapor annealing, which is usually carried out on P3HT/fullerene solar cells. Although additives such as 1,8-octanedithiol are added into the solution to help separate donor and acceptor domains, this separation cannot be controlled precisely. Therefore, NIL would provide an effective solution if an ordered active layer morphology could be formed by it. However, so far no results have been published that show that NIL can be applied to a wide variety of materials in the polymer solar cell field. Now, the UT Dallas team has utilized NIL to pattern the low bandgap (1.4 eV) solar cell polymer PCPDTBT. For the first time, they have used NIL to fabricate high quality nanogratings for this polymer. "After carefully optimizing the nanograting geometry, we were able to achieve a high solar cell efficiency of 5.5%," notes Yang. Furthermore, this work demonstrates that NIL is not only limited to solar cells made of the most widely studied polymer P3HT, but also can be applied to a wide variety of materials used in the fabrication of polymer solar cells low bandgap polymers can also be patterned by this technique to make efficient devices. Despite considerable effort, the highest reported power conversion efficiencies obtained from nanoimprinted P3HT solar cells have been in the 3-4% range. These values are lower than the highest values (∼4-5%) when the same polymer is used in a bulk heterojunction structure. "This indicates that NIL works better for low bandgap polymer solar cells," says Yang. "One possible explanation is that the method of using thermal or solvent vapor annealing to control the phase separation in P3HT based bulk heterojunction solar cells is very effective, as shown by a number of studies; while that of using additives in the low bandgap polymer solar cells is not, as described in literature." "This less effective approach leaves NIL more space to demonstrate its advantage in improving the solar cell performance when compared to the bulk heterojunction structure," he concludes. "This is our preliminary thinking and more studies are required to understand these different behaviors. Also as predicted in our recent study, a larger interface area between polymer and fullerene is preferable for efficient devices. A practical way to further increase it is needed as well. Our future work will focus on these aspects." Source: Nanowerk (http://www.nanowerk.com/spotlight/spotid=38076.php)
Categories: National Nanomanufacturing Network