Perovskite solar cells become even more promising with cheaper materials

first_img(a) Cross-section schematic of a perovskite solar cell with copper iodide hole conductor. (B) Image of the complete device. SEM cross-section images of solar cells using (C) copper iodide and (D) spiro-OMeTAD hole conductors. Credit: Christians, et al. ©2013 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. Dye-sensitized solar cells rival conventional cell efficiency Explore further Citation: Perovskite solar cells become even more promising with cheaper materials (2014, January 7) retrieved 18 August 2019 from ( —Due to their rapid improvements in a short amount of time, perovskite solar cells have become one of today’s most promising up-and-coming photovoltaic technologies. Currently, the record efficiency for a perovskite solar cell is 15% and expected to improve further. Although the perovskite material itself is relatively inexpensive, the best devices commonly use an expensive organic hole-conducting polymer, called spiro-OMeTAD, which has a commercial price that is more than 10 times that of gold and platinum.center_img Journal information: Journal of the American Chemical Society More information: More information: Jeffrey A. Christians, et al. “An Inorganic Hole Conductor for Organo-Lead Halide Perovskite Solar Cells. Improved Hole Conductivity with Copper Iodide.” Journal of the American Chemical Society. DOI: 10.1021/ja411014k In a new study, Jeffrey A. Christians, Raymond C. M. Fung, and Prashant V. Kamat from the University of Notre Dame in Indiana have found that copper iodide, an inexpensive inorganic hole-conducting material, may serve as a possible alternative to spiro-OMeTAD. Although the efficiency of perovskite solar cells containing copper iodide measured in this study is not quite as high as those containing spiro-OMeTAD, the copper iodide devices exhibit some other advantages that, overall, suggest that they could lead to the development of inexpensive, high-efficiency perovskite solar cells.”The hole conductor is currently the most expensive part of perovskite solar cells,” Christians told “Other organic hole conductor alternatives to spiro-OMeTAD have been investigated, but these alternatives still remain very expensive. This is the first reported inorganic hole conductor for perovskite solar cells, and is much less expensive than previously reported hole conductor materials. This low-cost hole conductor could further lower the cost of these already inexpensive solar cells.”Perovskite solar cells, as a whole, are attractive because perovskite is a class of materials with a particular crystal structure that is the same as that of calcium titanium dioxide. This structure gives solar cells high charge-carrier mobilities and long diffusion lengths, allowing the photo-generated electrons and holes to travel long distances without energy loss. As a result, the electrons and holes can travel through thicker solar cells, which absorb more light and therefore generate more electricity than thin ones.Although this study marks the first time that copper iodide has been investigated for use as hole conductors in perovskite solar cells, copper-based hole conductors have previously shown promise for use in dye-sensitized and quantum dot-sensitized solar cells. Part of their appeal is their high conductivity. In fact, copper iodide hole conductors exhibit an electrical conductivity that is two orders of magnitude higher than spiro-OMeTAD, which allows for a higher fill factor, which in turn determines the solar cell’s maximum power.Despite the copper iodide’s high conductivity, the results of the current study showed that perovskite solar cells made with copper iodide hole conductors have a power conversion efficiency of 6.0%, lower than the 7.9% measured here for cells with spiro-OMeTAD hole conductors. The researchers attribute this shortcoming to the fact that spiro-OMeTAD solar cells have exceptionally high voltages. In the future, they think that the voltages of copper iodide solar cells can be increased, in particular by reducing the high recombination rate. The researchers calculated that, if they could achieve the highest parameter values observed in this study, the resulting copper iodide solar cell would have an efficiency of 8.3%.The researchers also observed that the copper iodide solar cells exhibited another surprising advantage, which is good stability. After two hours of continuous illumination, the copper iodide cells showed no decrease in current, while the current of the spiro-OMeTAD cells decreased by about 10%. The researchers plan to further improve the devices in the future.”We are currently working to understand the cause of the low voltage in copper iodide-based perovskite solar cells,” Christians said. “With further work, we aim to increase the stability and improve the efficiency of these solar cells above 10%. “The biggest challenge facing perovskite solar cells is long-term stability in a wide range of environments. The efficiency of the best perovskite solar cells is competitive with current commercial technologies, and they are potentially much cheaper. However, commercial solar cells must last 20-30 years with minimal degradation, and whether or not perovskite solar cells are capable of this type of long-term stability is currently an unanswered question.” © 2014 Phys.orglast_img read more

Scientists solve puzzle of turning graphite into diamond

first_img New diamond harder than a jeweller’s diamond, cuts through ultra-solid materials © 2017 These simulations are based on the prediction that, at these pressures, less energy is required to form the cubic diamond nucleation core, or nucleus—the starting point of diamond growth—than to form the hexagonal diamond nucleus. Since forming this nucleus is the most energy-consuming step of the entire process, it follows that cubic diamond formation should be more thermodynamically favorable than hexagonal diamond.But a major drawback of these simulations is that they do not account for the interfaces between the graphite and the diamond nuclei: a lattice mismatch between the two surfaces can induce a strain energy that can interfere with the stability of the growing diamond. Using a novel simulation called stochastic surface walking, the researchers in the new study could more thoroughly explore all of the possible interfaces and identify seven of them that correspond to the lowest-energy intermediate structures in the graphite-to-diamond transition. Overall, the results show that the interface between graphite and the hexagonal diamond nucleus is less strained and more stable than the interface with the cubic diamond nucleus. Accounting for the stability of these interfaces can finally explain why hexagonal diamond forms much more easily and quickly than cubic diamond at moderate pressures.The researchers added that, although cubic diamond may appear to be more desirable than hexagonal diamond to the average person, both materials have their advantages.”While cubic diamond is familiar in everyday life and is a highly useful material, hexagonal diamond could also be very useful,” Liu said. “For example, it was predicted by theory to be even harder than cubic diamond. While the hexagonal diamond (lonsdaleite) can be found in meteorites, the production of large hexagonal diamond crystals has not been achieved in experiment. One would therefore expect that large hexagonal diamond crystals, if produced, would be even more precious than cubic diamond.”In the future, the researchers are planning to further improve the simulations by incorporating techniques from neural networks as well as by using big data. Stochastic surface walking simulations can explain why graphite turns into hexagonal, not cubic, diamond under pressures of 5-20 gigapascals. Credit: Xie et al. ©2017 American Chemical Society Journal information: Journal of the American Chemical Society (—Researchers have finally answered a question that has eluded scientists for years: when exposed to moderately high pressures, why does graphite turn into hexagonal diamond (also called lonsdaleite) and not the more familiar cubic diamond, as predicted by theory? More information: Yao-Ping Xie et al. “Graphite to Diamond: Origin for Kinetics Selectivity.” Journal of the American Chemical Society. DOI: 10.1021/jacs.6b11193 Explore further The answer largely comes down to a matter of speed—or in chemistry terms, the reaction kinetics. Using a brand new type of simulation, the researchers identified the lowest-energy pathways in the graphite-to-diamond transition and found that the transition to hexagonal diamond is about 40 times faster than the transition to cubic diamond. Even when cubic diamond does begin to form, a large amount of hexagonal diamond is still mixed in.The researchers, Yao-Ping Xie, Xiao-Jie Zhang, and Zhi-Pan Liu at Fudan University and Shanghai University in Shanghai, China, have published their study on the new simulations of the graphite-to-diamond transition in a recent issue of the Journal of the American Chemical Society.”This work resolves the long-standing puzzle of why hexagonal diamond is preferentially produced from graphite instead of the cubic diamond at the onset of diamond formation,” Liu told “Considering that graphite-to-diamond is a prototype solid-to-solid transition, the knowledge learned from this work should greatly benefit the understanding of high-pressure solid physics and chemistry.”Graphite, hexagonal diamond, and cubic diamond are all carbon allotropes, meaning they are made of carbon atoms that are arranged in different ways. Graphite consists of stacked layers of graphene, whose atoms are arranged in a honeycomb-like lattice. Since the carbon atoms in graphene are not fully bonded, graphene is soft and flakes easily, making it ideal for use as pencil lead.Both types of diamond, on the other hand, consist of carbon atoms that all have the maximum four bonds, which explains why diamond is so hard. In cubic diamond (the kind typically found in jewelry), the layers are all oriented in the same direction. In hexagonal diamond, the layers are alternately oriented, giving it a hexagonal symmetry.Under high pressures of more than 20 gigapascals (nearly 200,000 times atmospheric pressure), theory and experiment agree that graphite turns into cubic diamond, with some hexagonal diamond mixed in. But under pressures of less than 20 gigapascals, simulations have always predicted that cubic diamond should be the favored product, in contrast with experiments. Citation: Scientists solve puzzle of turning graphite into diamond (2017, February 23) retrieved 18 August 2019 from 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

Playing it safe with royalty

Raw silks, heavy brocade, intricate thread work, linen and some striking silhouettes – Samant Chauhan’s Poshak was about the royalty of fabric and smart use of colour. The opening emsemble in a flowy fiery orange accessorised with a jacket with heavy flower work was not matched up but the rest of the collection where he played very safe and stuck to beiges and pale whites occasionally adding a hint of red and gold. Pearl, lace additions and rich golden tassles added to the splendor Chauhan wanted to portray – but compared to the other designer he was showcasing with – the collection was not sufficiently striking. Showstopper Manoj Bajpai in a brown raw silk jacket with golden medallions and linen pants was another safe bet for this collection. read more

People should be aware of live music

first_imgDelivered fresh from The Netherlands, the Spinifex Orchestra were in town recently to rock the Capital. Not adhering to your usual larger-than-life orchestra concept, the four-musician band gave the city a taste of the live music experience. We caught up with them about their India story, performing in Delhi, plans for the future and more. Here are excerpts: Tell us a bit about yourselves. A little history. Where did Spinifex Orchestra start from? Was there an idea behind the conception of a tradition that brought it about? Also Read – ‘Playing Jojo was emotionally exhausting’It all started with a band called Bhedam. A band which consisted of four musicians from The Netherlands and two percussionists from Bangalore. It was way back in 2001 and 2002 that we had collaborated with Indian musicians and it had taught us a lot. We took lessons from Jahanavi Jaiprakash, but it all changed with her sad demise in 2002. That was of the end of Bhedam. But the rest of the orchestra members felt the need of a larger band and thus in 2006, Spinifex was formed. It was a nine-piece band originally. Also Read – Leslie doing new comedy special with Netflix We were involved with different projects and that is how Spinifex grew. There were a couple of other bands namely — Tubaband, Indian Spinifex — which we had formed as a part of our crossover with Indian musicians. We finally thought we need to be flexible as a regular orchestra and finally a smaller band with five members were formed. How many members and how long have you performed together?Well it is a five-member band with Tobias Klein on the saxophone, Jasper Stadhoulders on the guitar, Goncalo Almeida on the bass, Philipp Moser on the drums and Gijs Levelt on the trumpet. But Gijs isn’t touring India with us this time and we miss him a lot. We have been playing together for three years now. How has India treated you so far? Is this your first India tour?We all like India very much. It has always been great to come here and perform. Tobias is touring India for the fifth time but it’s the first tour for the others. How has Delhi treated you?This place (India Habitat Centre) is unlike other places I have seen in India before. I had been to Khan Market the last time I toured India and that place was quite impressive. Delhi has always been warm to us and has shown tremendous support throughout. What sort of audience and feedback are you expecting from Delhi?(Laughs) Well you saw that! People who enjoy live music and want to experience it first hand.What plans for 2013 and what plans post Delhi? We are recording next week in Amsterdam. We’ll be touring Portugal in July. Various tours and events are lined up in The Netherlands after that.Do you find takers in this age of electronic dance music and pop? People are always curious to hear new things and that is always going to be the case. There are audiences who prefer to experience live music.Do people need to be made more aware about orchestra music?People should be made aware about live music. The culture is picking up fast. Experiencing live music is very important in the rapidly evolving music environment. Has there been a shift in the trend of how orchestras were perceived earlier and nowadays?Not really, if you ask me. There is no distinction between orchestra music and music with singing.last_img read more

Down the memory lane

first_imgThe works on display talk about going down memory lane, the artists have chosen to represent a phase and moment from their lives.As Priyanka speaks about her art, ‘Every painting of mine is a moment which I’ve lived at some point in my life. A series of some significant moments together made this show happen. I’m playing them as a reel of my real life. These all together has created the person who I am today.’The works on display speak of a collective consciousness rather than individual approach to life. Also Read – ‘Playing Jojo was emotionally exhausting’They are colourful threads that have been picked on the way of life, making a multi coloured ball of episodic memories. It’s about being- a child; a woman; an Indian; an artist; a philosopher and multiple roles. It talks about connection, continuity and growth. Similarly Gayatri speaks about her art works as, ‘visual shorthand for painting everyday-life’s mundane schedule. What makes them special is their directness and child-like simplicity, the works are narrative and allegorical; they tell the story not one that I wishes to narrate rather the one which the viewer or subject creates.’When: On till January18Where: India Habitat Centerlast_img read more

Lankan PM Navy has right to shoot anyone who intrudes

first_img“Sri Lanka Navy has the right to shoot in any part of the country at anyone who enters the bodies (waters), it’s nothing new,” he told NDTV.Wickeramasinghe’s remarks assume significance in the context of the visit of Modi to Sri Lanka during the weekend when he had discussed the issue of Indian fishermen–a major irritant in bilateral ties–with President Mithripala Sirisena.He said Modi’s visit to the country was “successful”.The two nations are trying to resolve the fishermen issue, he said. The Prime Minister reached out to Sri Lanka and the Sri Lankans also responded, he added. Also Read – Pro-Govt supporters rally as Hong Kong’s divisions deepenDuring the visit, Modi had made clear that this complex question–of Indian fishermen–involves livelihood and humanitarian concerns on both sides.“This complex issue involves livelihood and humanitarian concerns on both sides. We should handle it from this perspective. At the same time, we need to find a long term solution to this issue,” Modi had said.Ahead of Prime Minister Modi’s visit, Wickremasinghe had told a Tamil news channel, “If someone tries to break into my house, I can shoot. If he gets killed… Law allows me to do that,” drawing India’s ire.last_img read more

Magical 90s

first_imgDo you remember these iconic events of ‘90s? Like the Bombay serial blasts, Sushmita Sen crowned Miss Universe, Nelson Mandela became the first black president of South Africa, the shocking demise of Princess and the biggest invention of all times – Google.Following on the success of last year’s The 80s: The Decade That Made Us, National Geographic Channel is set to debut the network’s next epic mini-series – The 90s: The Unforgettable Decade on May 15, at 10 pm.   Also Read – ‘Playing Jojo was emotionally exhausting’The 90s will celebrate the people, the inventions and the decisions that shaped our current world, told from the perspective of the history makers, celebrities, politicians and musicians who created these iconic moments. Were they 10 years of exuberance, or 10 years of missed warnings?  The series will be reliving the decade through ‘inside out’ storytelling and analysis. The series includes interviews — from unsung heroes behind the decade’s most riveting stories to the biggest names in politics, tech, movies and music.  Also Read – Leslie doing new comedy special with NetflixThe series begins with The 90s Exposed:  From Nelson Mandela’s prison release and the rise of Bill Clinton to the birth of the ‘virtual world’, a star-studded cast explores the most iconic moments, people and innovations of the 1990s. The climax of the series will be a 2-part India special – The 90s- India Rediscovered and The 90s- The Great Indian Dream that dives deep to unfold India’s transformation, filled with emotion, tragedy and drama.last_img read more

Iftar nights at jamia

first_imgJamia which means ‘university’ in Arabic, is a name bestowed upon Jamia Nagar, an area in south Delhi with muslim majority. The area is in proximity to Jamia Millia Islamia, a prestigious university in the national Capital. During the month of Ramzan, this inexpensive colony is well-decorated. The area which is otherwise congested, seems deserted during the day time, as people prefer to stay at their homes while fasting. Also Read – ‘Playing Jojo was emotionally exhausting’Iftar preparation begins earlier in the evening and people break their fast after a loud siren, which marks the exact time of eating.“Ramzan brings us closer to our family. We eat, pray and shop together. It is a great feeling”, said Hammad Kamal, a Batla House resident. The male members start moving towards the nearby mosques to offer tarawee post iftar, while the women and children burst out of their homes to the nearby markets. This paradise for non-vegetarians has a lot to treat their bellies. Biryani shops are the highlight of this market. Bilal, Hammad and Salman chicken biryani are a few such names. Also Read – Leslie doing new comedy special with NetflixAs a result of the University’s proximity, a large number of students who reside in the nearby colonies in paying guests and apartments also come here to cherish the festivities. As Eid is round the corner— plenty of shops, like those at Chandini Chowk, attract people who are interested in shopping for bangles, street snacks, show pieces and clothes.Plenty of refreshments are available from sherbets to lime juice. Furthermore, small vendors of fruits, dates, kebabs and lip smacking chicken delicacies are strewn around the market.Jama Masjid Abubaqar Siddique is the Central Mosque of Jamia Nagar—it is a huge beautiful white building with green borders and square shaped windows. Heaps of  straw, bound and stacked in circles make it very difficult to spot the shopkeeper, dwarfed behind, busy doing his business. He and his neighbour Raju, a paan seller, both love this period of Ramzan. “It is the most happening period of the year, I earn the most during this time,” said Raju.By 4 am, people go back to their homes and the shopkeepers after wrapping up their accounts, shut their shops and pray.last_img read more