Nanocones could be key to making inexpensive solar cells

first_img Explore further (Phys.org) — One of the biggest challenges facing the silicon photovoltaic industry is making solar cells that are economically viable. To meet this goal, the module cost, which is currently about $1/watt, needs to be decreased to just half that. Much of this cost comes from the silicon material and the expensive fabrication processes often used. In a new study, a team of scientists and engineers has demonstrated that a hybrid solar cell covered in silicon nanocones and a conductive organic polymer can address both cost-cutting areas while providing excellent performance. Citation: Nanocones could be key to making inexpensive solar cells (2012, June 5) retrieved 18 August 2019 from https://phys.org/news/2012-06-nanocones-key-inexpensive-solar-cells.html USC team develops promising polymer for solar cells Journal information: Nano Letters Copyright 2012 Phys.org All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.center_img More information: Sangmoo Jeong, et al. “Hybrid Silicon Nanocone-Polymer Solar Cells.” Nano Letters. DOI: 10.1021/nl300713x (a) Fabrication process of the solar cells, in which silicon nanocones are coated with a polymer. (b), (c), and (d) show scanning electron microscope images of the nanocones after each step. Image credit: Jeong, et al. ©2012 American Chemical Society This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. The researchers, led by Professor Yi Cui and Professor Michael D. McGehee from Stanford University, have published their study in a recent issue of Nano Letters.The hybrid solar cells’ use of nanoscale texturing has two advantages: it improves light absorption and reduces the amount of silicon material needed. Previous nanoscale texturing of solar cells has involved nanowires, nanodomes, and other structures. Here, the researchers found that a nanocone structure with an aspect ratio (height/diameter of a nanocone) of around one provides an optimal shape for light absorption enhancement because it enables both good antireflection (for short wavelengths of light) and light scattering (for long wavelengths). In previous designs using nanoscale texturing, the space between structures has normally been too small to be filled with polymer, so a full second layer is required. But the tapered nanocone structure demonstrated here allows for the polymer to be coated in the open spaces, eliminating the need for other materials. By forming this nanocone/polymer hybrid structure with a simple, low-temperature method, processing costs are also reduced.After testing the solar cell and making some improvements, the researchers produced a device with an efficiency of 11.1%, which is the highest among hybrid silicon/organic solar cells to date. In addition, the short-circuit current density, which indicates the largest current that the solar cell can generate, is only slightly lower than the world record for a monocrystalline silicon solar cell, and very close to the theoretical limit. Due to the hybrid silicon nanocone-polymer solar cells’ good performance and inexpensive processing, the researchers predict that they could one day be used as economically viable photovoltaic devices.last_img read more

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Graphene quantum dot flash memories look promising for data storage

center_img Explore further More information: Soong Sin Joo, et al. “Graphene-quantum-dot nonvolatile charge-trap flash memories.” Nanotechnology 25 (2014) 255203 (6pp). DOI: 10.1088/0957-4484/25/25/255203 To overcome this problem, researchers have recently been working on storing charge in discrete charge traps, such as nanocrystals, instead of polysilicon layers. Since discrete charge trap materials have the advantage of preventing unwanted charge movement as a result of their lower sensitivity to local defects, they offer the potential for high-density flash memories.Now in a new study, scientists have used graphene quantum dots instead of nanocrystals as the discrete charge trap material. The researchers, Soong Sin Joo, et al., at Kyung Hee University and Samsung Electronics, both in Yongin, South Korea, have published their paper on graphene quantum dot flash memories in a recent issue of Nanotechnology.Although graphene in general is widely known as an attractive material for next-generation electronics and photonics because of its unique properties, the development of graphene memory devices is still at an early stage. Graphene quantum dots in particular are very new materials. As bits of graphene extracted from bulk carbon, graphene quantum dots can be engineered with specific electronic and optical properties for different purposes.Here, the researchers prepared graphene quantum dots of three different sizes (6, 12, and 27 nm diameters) between silicon dioxide layers. The researchers found that the memory properties of the dots differ depending on their sizes. For instance, while the 12-nm dots exhibit the highest program speed, the 27-nm dots exhibit the highest erase speed, as well as the highest stability.”This is the first report of charge-trap flash nonvolatile memories made by employing structurally characterized graphene quantum dots, even though their nonvolatile memory properties are currently below the commercial standard,” coauthor Suk-Ho Choi at Kyung Hee University told Phys.org. “Actually, this is first successful application of graphene quantum dots in practical devices, including electronic and optical devices, as far as I know, even though there are many reports on physical and chemical characterizations of graphene quantum dots.”As flash memory devices in their early stages of development, the graphene quantum dot memories demonstrate a promising performance, with an electron density comparable to that of memory devices based on semiconductor and metal nanocrystals. The researchers hope that future improvements to the devices will lead to enhanced performance and new applications.”If flexible dielectrics (insulators) are used instead of silicon dioxides as tunnel and control barriers on plastic substrates, then they can be used in flexible (or wearable) electronic devices,” Choi said. “Metal nanoparticles also offer several advantages similar to graphene quantum dots, such as higher density of states, flexibility in choosing the work function, etc., for charge-trap flash nonvolatile memories, but may potentially degrade the device performance due to their thermal instabilities and are not useful for transparent and flexible electronics and photonics.” This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

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Tropical bats found to use carotenoids for skin coloration

first_imgA Honduran white bat. Credit: Geoff Gallice/Wikipedia/CC BY 2.0 Carotenoids are deeply colored photosynthetic pigments produced in plants, which animals use to prevent oxidative damage and to color external tissues. However, because animals can’t synthesize their own carotenoids, they rely on plant dietary sources. Mammals, including humans, are particularly limited in this regard by comparison with other classes, which often have brightly colored external markings and patterns produced by carotenoids. By contrast with the brightly colored feathers and scales of birds, reptiles and fish, mammals have only small amounts of carotenoids in their skin and seemingly none in their hair.Humans particularly rely on photosynthetic carotenoids for their provitamin A value, their immunostimulatory functions and antioxidant properties. Carotenoids are more highly concentrated in internal tissues than the skin, particularly in the macula of the eye. After consumption, carotenoids are carried through the bloodstream by lipoproteins—read dietary fats—to target tissues. Humans are thus particularly dependent on consuming dietary fat to ensure the bioavailability of carotenoids, which makes the choice between 0 percent and full-fat Greek yogurt much easier (and more delicious).The white fruit bat’s skin is a distinctive yellow, and particularly noticeable in hairless external features of the ears and nose, the integument. The researchers used high-performance liquid chromatography in combination with time-of-flight mass spectrometry in order to determine the specific carotenoid expressed in the bat’s skin. They theorize that the bat’s dietary source for lutein is the red ripe fruit of the Ficus colubrinae fig tree. Notably, the lutein in the skin of the bats contains esters, while their hepatic luteins were not esterified, indicating the biological ability to esterify lutein. “Although the nutritional use of xanthophylls [like lutein] may require esters to be metabolized, the fact that bats are able to esterify them into their integument opens up interesting possibilities for improving the benefits of xanthophylls to human health,” the authors write.In their report, the authors also speculate on the adaptive advantage of the bat’s ability to esterify lutein in its skin. Esterified xanthophylls provide plants with stability, and the bats might receive some benefit from achieving longer-lasting skin coloration. For instance, the Honduran white fruit bat is highly social, congregating and roosting together; such gregarious behavior is highly linked with the development of distinctive visual cues like coloration for communication purposes. “Altogether,” the authors conclude, “these results call into question the commonly neglected role of vision in bat communication and suggest microbats may have evolved color traits despite constraints imposed by nocturnal habitats.” More information: Tropical bat as mammalian model for skin carotenoid metabolism. PNAS (2016) DOI: 10.1073/pnas.1609724113AbstractAnimals cannot synthesize carotenoid pigments de novo, and must consume them in their diet. Most mammals, including humans, are indiscriminate accumulators of carotenoids but inefficiently distribute them to some tissues and organs, such as skin. This limits the potential capacity of these organisms to benefit from the antioxidant and immunostimulatory functions that carotenoids fulfill. Indeed, to date, no mammal has been known to have evolved physiological mechanisms to incorporate and deposit carotenoids in the skin or hair, and mammals have therefore been assumed to rely entirely on other pigments such as melanins to color their integument. Here we use high-performance liquid chromatography (HPLC) in combination with time-of-flight mass spectrometry (HPLC-TOF/MS) to show that the frugivorous Honduran white bat Ectophylla alba colors its skin bright yellow with the deposition of the xanthophyll lutein. The Honduran white bat is thus a mammalian model that may help developing strategies to improve the assimilation of lutein in humans to avoid macular degeneration. This represents a change of paradigm in animal physiology showing that some mammals actually have the capacity to accumulate dietary carotenoids in the integument. In addition, we have also discovered that the majority of the lutein in the skin of Honduran white bats is present in esterified form with fatty acids, thereby permitting longer-lasting coloration and suggesting bright color traits may have an overlooked role in the visual communication of bats. Journal information: Proceedings of the National Academy of Sciences Explore further Citation: Tropical bats found to use carotenoids for skin coloration (2016, October 10) retrieved 18 August 2019 from https://phys.org/news/2016-10-tropical-carotenoids-skin.htmlcenter_img © 2016 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Breeding better broccoli (Phys.org)—In the pursuit of greater carotenoid bioavailability to ensure human health, researchers have sought other animal models of carotenoid function. Recently, a collaborative of biologists in Spain and Costa Rica published the results of a study in the Proceedings of the National Academy of Sciences demonstrating that frugivorous Honduran white bats color their skin with the deposition of the carotenoid lutein—the primary carotenoid for the preservation of the macula in human eyes. This is the first time a mammal has been shown to concentrate high levels of carotenoids in skin, and thus may provide a model for the understanding and enhancement of carotenoid function.last_img read more

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Why invest in Belarus

first_imgDirect access to the market of the Customs Union and Common Economic Space (Belarus, Russia, and Kazakhstan); abolition of internal customs barriers; completion of the formation of Common Economic Space; liberalization of foreign exchange transactions; the country’s geographical position; the intersection of rail and road routes, oil and gas pipelines, communication systems, water and air communications between the industrialized Western Europe and Asia are some of the reasons why one should invest in Belarus. Also Read – ‘Playing Jojo was emotionally exhausting’There is also political, social and economic stability. The country also has an abundance of skilled labour. The state relies on public-private partnership. A key advantage for investing in Belarus is reducing of the share of public sector and privatization of state property. This ensures efficient use of resources.For large strategic enterprises of Belarus refused to quick sale of state assets. National legislation provides for various forms of investor participation in the privatization process. The Investment Agreement with the Republic of Belarus provides investors with additional incentives and preferences. This allows the investor to establish additional safeguards to protect their capital and also get preferential treatment and incentives for the investment project.last_img read more

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Of melody and memories

first_imgRang-E-Khusro – a two-day concert showcasing the life and works of Hazrat Amir Khusro was organised by Sakshi and Siet at India Habitat Centre recently. The first of the two day programme of poetry and music showcased a jugalbandi – ashaar and sitar, where renowned Sitar Maestro, Sudeep Rai accompanied by Ustad Rashid Zafar Khan (Tabla) flawlessly executed a masterly performance enhancing and building on the Poetic Reflections by well known litterateur and poet, Nazim Naqvi.  Also Read – ‘Playing Jojo was emotionally exhausting’The magical blend of the spoken word, reflecting on Hazrat Amir Khusro’s work mingling with the speaking strains of the sitar was unimaginably beautiful and had the audience spellbound.The second day featured Kalaam-E-Khusro – a mesmerising sufi vocal by Ustad Shakeel Ahmed and Vaishali Rai accompanied by Ustad Salim Ahmed Khan (Tabla), Ustad Syed Rehman Khan (Sarangi) and Anees Ahmed (Keyboard) on the second day. The beautiful Sufi kalaam Piya Ghar Aaye… melodiously sung by Vaishali Rai  opened the evening.  Then came a virtual feast of Sufi kalaams  in Shakeel Ahmed’s solo and duet act, presenting mesmerizing Sufi songs in his unique style which included songs like ChhaapTilak.. and Dama Dum Mast Kalandar amongst others.  Also Read – Leslie doing new comedy special with NetflixShakeel Ahmed treated the audience to the delectable farsee Amadabaqatl e man as also the khadi boli song Kahe ko byahi bides, exhibiting Hazrat Amir Khusro’s ease and mastery over these languages. Ahmed transported his listeners into Amir Khusro’s world of universal emotions, humanity and love. It was amazing to see such a houseful overflowing audience on two of the coldest and most foggy December nights making a perfect weekend for Delhiites.last_img read more

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Elusive tiger found dead inside Baghghora forest

first_imgKolkata: The Royal Bengal tiger which was spotted by the local villagers inside the forest areas of West Midnapore, Jhargram and Bankura on several occasions since early March, was found dead inside Baghghora forest, around 25 Km away from Lalgarh in Jhargram district.It was first spotted on March 2 by a camera which was installed in Lalgarh forest. Despite several attempts by the state forest department it could not be captured in the past one-and-a-half month. Also Read – Heavy rain hits traffic, flightsA senior official of the state forest department has said the tiger was found dead with various injury marks on its body. The reason of its death is yet to be confirmed by the department after the autopsy is done.”We heard that several injury marks were there on its body indicating that it might have been killed by local tribes. After post-mortem, we can confirm how the big cat was killed,” a senior forest department official added.He also said the local villagers essentially the tribes who go for hunting during this time of the year to celebrate their hunting festival were asked not to go into the forest as animals might prove to be fatal. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedIt was alleged that those taking part in the hunting festival might have killed the tiger as a spear was found stuck in the throat of the animal when its carcass was removed by the forest department officials. Forest officials had earlier said the tiger might have sneaked into the forest from Simlipal reserve in neighbouring Odisha.The forest department officials and police faced difficulties to remove the animal from the area as hundreds of villagers had gathered around the scene. Questions have been raised on why the forest department officials allowed the local villagers to conduct the hunting festival after pugmarks were found two days ago near Lalgarh. The forest department took several steps including the use of drones to detect the presence of the tiger. A few days ago, the tiger was spotted by the villagers who tried to capture the animal by the help of a huge net. The tiger managed to flee before the forest officials reached the spot. The carcass of the animal was taken to Midnapore for post mortem.It is an unfortunate incident and a sad day for Bengal as well. Forest officials had put in best efforts to catch it but they failed. There was always a threat to the tiger as it was straying in the villages, adjoining to the forests, said former Atanu Raha, former Principal Chief Conservator of Forests.”Since presence of the tiger was confirmed in Lalgarh forest, our men had tried their best to catch the big cat. But unfortunately, we failed to rescue it alive,” state forest minister Binay Krishna Burman.last_img read more

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SMST of IIT KGP to launch new programmes

first_imgKolkata: The School of Medical Science and Technology of IIT Kharagpur will launch new programmes from the upcoming academic session, a statement issued by the institute said today. The objective is to simultaneously train students and researchers on engineering and medical science, the statement said.The new courses will also include a 2-year M Tech in Biomedical Engineering.The school already runs a 3-year Masters in Medical Science and Technology, a unique programme of its kind with MBBS doctors being admitted in the domain of medical technology. Also Read – Heavy rain hits traffic, flightsThere will also be a joint MSc-PhD programme with the Tata Medical Center, Kolkata from the coming academic session in the areas of molecular medical microbiology, nuclear medicine and medical physics.The head of the School of Medical Science and Technology, IIT Kharagpur, Prof Suman Chakraborty said, “These programmes would bridge the gap among medicine, biological sciences and engineering with a road map to develop world-class scientists.” IIT KGP is also in the process of launching a 400-bed super speciality hospital which is expected to be operational by 2019.last_img read more

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Two girls found dead on railway tracks near Uluberia

first_imgKolkata: Mystery shrouds the death of two girls whose bodies were found on the railway tracks near Uluberia station on late Saturday night.Police are yet to confirm whether the victims had committed suicide by throwing themselves in front of a running train or there was any foul play behind the incident. According to circumstantial evidence, the investigators suspect that the victims might have committed suicide by jumping before a train. The exact cause is yet to be ascertained by the police. Some locals spotted two bodies lying on the railway tracks near Dompara crossing at around 10.30 pm on Saturday and they reported the matter to the railway police. They rushed to the spot and recovered the bodies. Two bags were found on the spot, which might belong to those two. According to a preliminary investigation, police suspect that the victims might have been friends who had decided to end their lives. No suicide note was, however, found from their bags. The cause behind taking this drastic step is yet to be ascertained by the police. Also Read – Heavy rain hits traffic, flightsA local told police that some of his friends went there with an intension to sit near the railway tracks when they spotted the two bodies and reported the matter to the railway police. After reaching the spot, the railway police officers found that the victims were already dead and there were multiple injury marks on their bodies. Police have sent the bodies for post-mortem. Police have started a probe to ascertain the identity of both the victims. All the nearby police stations have been informed.last_img read more

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Road rage hits attendance at Maruti factory

first_imgWorker attendance at Maruti Suzuki India Ltd here has been affected following an incident of road rage involving some of the employees and nearby villagers.A police complaint has been filed against more than 30 Maruti Suzuki workers employed at the company’s Manesar plant, a union leader said here on Tuesday.These workers were returning home in a company bus on Friday when the vehicle hit a car in Aliar village. “After heated arguments, the workers thrashed my 38-year-old brother very badly. He suffered fractures,” Jaiprakash, a resident of the village, said in his police complaint. Kuldeep Janghu, a Maruti union leader, said that some villagers had pledged to avenge the attack on the villager. “Some of our worried workers are not coming to work. The situation may turn grim if action is not taken on time,” Janghu said.last_img read more

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