University of Houston researchers have reported the first explanation for how perovskite materials change during production. The team’s goal was to find a more efficient way to absorb light, a critical step toward the large-scale manufacture of better and less-expensive perovskite solar panels.
Yan Yao, assistant professor of electrical and computer engineering and lead author on the paper said the study of the mechanism was how a perovskite thin film changes its microscopic structure upon gentle heating. That information is crucial for designing a manufacturing process that can consistently produce high-efficiency solar panels.
Last year Yao and other researchers identified the crystal structure of the non-stoichiometric intermediate phase as the key element for high-efficiency perovskite solar cells. But what happened during the later thermal annealing step remained unclear. The work is fundamental science, Yao said, but critical for processing more efficient solar cells.
“Otherwise, it’s like a black box,” he said. “We know certain processing conditions are important, but we don’t know why.”
The work also yielded a surprise: the materials showed a peak efficiency – the rate at which the material converted light to electricity – before the intermediate phase transformation was complete, suggesting a new way to produce the films to ensure maximum efficiency. Yao said researchers would have expected the highest efficiency to come after the material had been converted to 100 percent perovskite film. Instead, they discovered the best-performing solar devices were those for which conversion was stopped at 18 percent of the intermediate phase, before full conversion.
“We found that the phase composition and morphology of solvent engineered perovskite films are strongly dependent on the processing conditions and can significantly influence photovoltaic performance,” the researchers wrote in the paper. “The strong dependence on processing conditions is attributed to the molecular exchange kinetics between organic halide molecules and DMSO (dimethyl sulfoxide) coordinated in the intermediate phase.”
Perovskite compounds are commonly comprised of a hybrid organic-inorganic lead or tin halide-based material and have been pursued as potential materials for solar cells for several years. Yao said their advantages include the fact that the materials can work as very thin films – about 300 nanometers, compared with between 200 and 300 micrometers for silicon wafers, the most commonly used material for solar cells. Perovskite solar cells also can be produced by solution processing at temperatures below 150º Centigrade (about 300º Fahrenheit) making them relatively inexpensive to produce.
At their best, perovskite solar cells have an efficiency rate of about 22%, slightly lower than that of silicon at 25%. But the cost of silicon solar cells is also dropping dramatically, and perovskite cells are unstable in air, quickly losing efficiency. They also usually contain lead, a toxin.
Still, Yao said, the materials hold great promise for the solar industry, even if they are unlikely to replace silicon entirely. Instead, he said, they could be used in conjunction with silicon, boosting efficiency to 30% or so.
Yao is also a principal investigator at the Texas Center for Superconductivity at UH, which provided funding for the work.
The other researchers involved with the project include first author Yaoguang Rong, previously a postdoctoral fellow at UH and now associate professor at Huazhong University of Science and Technology in China; UH postdoctoral fellows Swaminathan Venkatesan and Yanan Wang; Jiming Bao, associate professor of electrical and computer engineering at UH; Rui Guo and Wenzhi Li of Florida International University, and Zhiyong Fan of Hong Kong University of Science and Technology.
This is very encouraging news for the perovskite field. The study also shows a quite disciplined research effort working on and taking apart each step in the preparation of a solar cell. It wasn’t likely exciting work to do, but the results are quite exciting indeed. Well done.
Researchers at Harvard’s School of Engineering and Applied Sciences have identified a whole new class of high-performing organic molecules that’s inspired by vitamin B2. Your humble writer likes these posts about making new ideas from suggestions sourced in unrelated fields most of all.
The new high-performing organic molecules can safely store electricity from intermittent energy sources like solar and wind power in large batteries.
This development builds on previous work in which the team developed a high-capacity flow battery that stored energy in organic molecules called quinones and a food additive called ferrocyanide. That advance was a game-changer, delivering the first high-performance, non-flammable, non-toxic, non-corrosive, and low-cost chemicals that could enable large-scale, inexpensive electricity storage.
While the versatile quinones show great promise for flow batteries, the Harvard researchers continued to explore other organic molecules in pursuit of even better performance. But finding that same versatility in other organic systems has been challenging.
Kaixiang Lin, a Ph.D. student at Harvard and first author of the paper said, “Now, after considering about a million different quinones, we have developed a new class of battery electrolyte material that expands the possibilities of what we can do. Its simple synthesis means it should be manufacturable on a large scale at a very low cost, which is an important goal of this project.”
Flow batteries are different because they store energy in solutions in external tanks, thus the bigger the tanks, the more energy they can store.
Back in 2014, Michael J. Aziz, the Gene and Tracy Sykes Professor of Materials and Energy Technologies at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), Roy Gordon, the Thomas Dudley Cabot Professor of Chemistry and Professor of Materials Science, Alán Aspuru-Guzik, Professor of Chemistry and their team at Harvard replaced metal ions used as conventional battery electrolyte materials in acidic electrolytes with quinones, molecules that store energy in plants and animals.
The last year they developed a quinone that could work in alkaline solutions alongside a common food additive.
In this most recent research, the team found inspiration in vitamin B2, which helps to store energy from food in the body. The key difference between B2 and quinones is that nitrogen atoms, instead of oxygen atoms, are involved in picking up and giving off electrons.
Professor Aziz fills us in with, “With only a couple of tweaks to the original B2 molecule, this new group of molecules becomes a good candidate for alkaline flow batteries. They have high stability and solubility and provide high battery voltage and storage capacity. Because vitamins are remarkably easy to make, this molecule could be manufactured on a large scale at a very low cost.”
Professor Gordon, co-senior author of the paper explains the basis on how the team made the technological cross connection, “We designed these molecules to suit the needs of our battery, but really it was nature that hinted at this way to store energy. Nature came up with similar molecules that are very important in storing energy in our bodies.”
The team will continue to explore quinones, as well as this new universe of molecules, in pursuit of a high-performing, long-lasting and inexpensive flow battery.
Harvard’s Office of Technology Development is already working closely with the research team to navigate the shifting complexities of the energy storage market and build relationships with companies well positioned to commercialize the new chemistries.
Flow batteries have huge potential, not just for solar or wind storage because of the real advantage of low cost and low, if any, toxicity. The main issue is weight, and that is a matter in mind as research and development marches on. The physical characteristic that adds complexity is simply pumping the liquid electrolyte back and forth during the charge and discharge cycles.
Ultimately a battery is valued by its charge capacity vs size and weight. Applications ultimately determine the other properties that a specific battery must have. Flow batteries can have a very wide range of applications as size weight and capacity improve. Where the technology can get to in the future is really a wild guess. GO Harvard!!
July 19, 2016 | 2 Comments
Brilliant Light Power, which we knew as Blacklight Power has developed the firm’s hydrino technology up to public demonstrations with measured and third party oversight. The known oversights include both academic and industrial representatives and now including major finance people. Dr. Randell Mills is on a roll.
The firm’s website has a useful press release out last week and lots of hydrino technical data to wade through. However, Brian Wang at NextBigFuture.com has assembled an excellent post that rapidly brings a reader up to date. The page is rich with all of it – text, photos and video. Its a pretty quick read through and explains things well.
If you’ve a mind to, click right on over to Wang”s page “Super controversial Brilliant Light Power aka Blacklight Power Claims to Be Generating Bursts of Megawatt Power and Claim Independent Validation”. Otherwise, or come back later, and we’ll deal with a few issues.
First off, is Dr. Mills credible? Over the years many thought to be credible folks have offered a logjam of commentary suggesting Dr. Mills has nothing there. Meanwhile they overlook the fact that saying such doesn’t make the remarks any more credible than Dr. Mills offerings. But Mills and his team are doing the work and publicly showing the results with third persons of unquantified objectiveness commenting. We’re way passed the sham fraud snake oil sales phase. Hydrinos are a replicated phenomena. Putting power on the grid, powering a large mobile device or other “Mass Media” satisfying proof is not. Yet.
The Brilliant Light Power folks that were Blacklight – and thankfully that name is gone – are still looking for the power emitting device to go commercial. The latest one offers net power, even though the energy capture is photovoltaic, thus not particularly efficient.
So there is lots of potential there. Plasma level temperatures, intense ultraviolet light, heat and lots of it.
Hydrinos, cold fusion, low energy nuclear reactions, alternative hot fusion and others are straining the scientific establishment. Real science that isn’t fitting up with how things are understood now poses adjustment and new concepts. Its not really a problem, at least for engineering and consumers, unless they listen too intently to the establishment. They are huge opportunities awaiting the insight, innovation and inventiveness needed to get to market.
Dr. Mills is closing in. Imagine that he can get effective hydrino producing energy into homes or cars at highly efficient rates at costs at or below current energy. A gallon of water vs one hundreds gallons of gasoline, or even a quarter of that – ? Sign me up.
Sandip Das, assistant professor of electrical engineering in the Southern Polytechnic College of Engineering and Engineering Technology, along with a team of three undergraduate research assistants, has recently fabricated the delicate solar cells, which are about 100 times thinner than a human hair.
Das said the future of solar power generation is in these flexible solar cells. He and his research team are investigating various nano-materials to fabricate the third-generation solar cells. The researchers hope to develop a superior photovoltaic technology that produces cheaper and more efficient solar cells.
David Danilchuk, an electrical engineering major who is an undergraduate research assistant on the project explained, “The most fascinating part of doing this research is the enormous potential that this new technology offers, such as integrating flexible solar cells on wearable electronics, backpacks and self-charging cell phones and electricity-generating layers on windows, especially on skyscrapers, and solar power’s ability to supply a large amount of clean, renewable and cheap energy for the future.”
In the laboratory, the research team fabricated the solar cells’ multiple nano-structured layers using a unique manufacturing process. Specialty instruments, like electron microscopes, as well as X-ray spectroscopy techniques and precision electronic measurement systems, enable the research team to investigate and better understand the cells’ behavior.
Baker Nour, an electrical engineering student and member of the research team, explained that the fabrication process developed by the team can produce these solar cells on plastic substrates to create flexible solar cells – one of the most advanced ideas in solar technology today.
In practice, these flexible solar panels can be beneficial after catastrophic storms. Disaster relief personnel could transport rolled-up solar panels to produce portable power on site, Das explained. Commercial building developers also are eyeing smart building applications, like transparent solar panels for windows, so skyscrapers can generate solar power and be more energy efficient.
Das explained current commercial solar panels use first-generation silicon solar cells, which are expensive, fragile and bulky, limiting their portability. The most promising materials systems for future generation solar cells are the materials that his research team applies in their fabrication – an ultra-thin hybrid Perovskite noncrystalline film. Rather than using expensive silicon, they fabricate their solar cells on cheap glass substrates like those in windows and beverage bottles.
The team plans to explore the fabrication process so they can develop solar cells on flexible plastics or metal foils, without requiring expensive materials, million-dollar equipment or scientific-grade clean rooms.
“For the past 20 years, efficiency of silicon solar cells could not be improved much after substantial research efforts globally,” Das said. He explained that silicon is not a good light absorber, and new technologies are needed to create high-efficiency cells at a lower cost. The new bandgap-engineered Perovskite crystals, which his team is investigating, can absorb a wider spectrum of sunlight compared to silicon, on a film that is 200 times thinner than silicon cells.
The implications for their research are still months away, but the team is confident that they will soon improve solar cells to attain higher efficiency, without the latest high-tech equipment or costly raw materials.
A major goal for their research is to substantially reduce the cost of producing solar cells.
Typically, solar cells are fabricated in a clean room, a controlled environment for manufacturing electronics that is free of dust or other contaminants. Even without a clean room, Das and his team are able to fabricate this next generation of solar cells and test their newly hatched cells.
“In the past 20 to 30 years of studying solar energy, researchers worldwide have learned how to cut costs tenfold,” Das said. “The raw materials used for the third-generation solar cells are less expensive than the electronic-grade silicon.”
A cutback in both material and fabrication costs means a significant reduction in the overall cost to produce electricity, ultimately saving consumers money.
“Our long-term goal is to bring the cost down to less than 10 cents per watt,” Das said. In the U.S., silicon solar cells currently cost about 30 cents per watt.
Das predicts that by 2040 solar power will become mainstream as researchers develop technologies to more efficiently use available space for power generation and solar cells become cheaper.
Danilchuk added, “For us, it’s exciting to be able to contribute to the field by sharing the knowledge that we obtain from our research and help advance the solar industry.”
Hopefully this is the future’s path. Now at triple the going rate for grid power solar hasn’t much real market power. Ten cents is getting very close and assuming that is an all costs in number lots more people will see the grid with less confidence.
Time is on solar’s side.- at least when the green environment folks hold political sway. Grid electrical rates are on a steep upward trend from political impacts on energy taking lowest cost production off line. That might just be what triggers wide spread solar success – if there is any wealth to buy in by then.
Researchers at the Paul Scherrer Institute (PSI) and the ETH Zurich have collaborated to develop a ground-breaking process for making solar fuel. The new procedure uses the sun’s thermal energy to convert carbon dioxide and water directly into synthetic fuel.
The team has unveiled a chemical process that uses the sun’s thermal energy to convert carbon dioxide and water directly into high-energy fuels: a procedure developed on the basis of a new material combination of cerium oxide and rhodium.
The discovery marks a significant step towards the chemical storage of solar energy. The researchers published their findings in the research journal Energy and Environmental Science. (Open access at this writing.)
Ivo Alxneit, chemist at the PSI’s Solar Technology Laboratory explained, “This allows solar energy to be stored in the form of chemical bonds. It’s easier than storing electricity. The new approach is based on a similar principle to that used by solar power plants.”
Alxneit and his colleagues use heat in order to trigger certain chemical processes that only take place at very high temperatures – above 1000 °C. Advances in solar technology will soon enable such temperatures to be achieved using sun light.
Alxneit’s research is based on the principle of the thermo-chemical cycle, a term comprising both the cyclical process of chemical conversion and the heat energy required for it – referred to by experts as thermal energy. Ten years ago, researchers had already demonstrated the possibility of converting low-energy substances such as water and the waste product carbon dioxide into energy-rich materials such as hydrogen and carbon monoxide.
That process works in the presence of certain materials such as cerium oxide, a combination of the metal cerium with oxygen. When subjected to very high temperatures above 1500 °C, cerium oxide loses some oxygen atoms. At lower temperatures, this reduced material is keen to re-acquire oxygen atoms.
Thus if water and carbon dioxide molecules are directed over such a cooled and activated surface, they release oxygen atoms. Water (H2O) is converted into hydrogen (H2), and carbon dioxide (CO2) turns into carbon monoxide (CO), whilst the cerium re-oxidizes itself in the process, establishing the preconditions for the cerium oxide cycle to begin all over again.
The hydrogen and carbon monoxide created in the process can be used to produce fuel: specifically, gaseous or fluid hydrocarbons such as methane, petrol and diesel. Such fuels may be used directly but can also be stored in tanks or fed into the natural gas grid.
Here’s the breakthrough. Up to now, this type of fuel production required a second, separate process known as the Fischer-Tropsch Synthesis, developed in 1925. The European research consortium SOLAR-JET recently proposed a combination of a thermo-chemical cycle and the Fischer-Tropsch procedure.
However, as Alxneit explains, “Although this basically solves the storage problem, considerable technical effort is necessary to carry out a Fischer-Tropsch Synthesis.” In addition to a solar installation, a second industrial-scale technical plant is required.
By developing a material that allows the direct production of fuel within one process, the new approach developed by Ivo Alxneit and his colleagues dispenses with the Fischer-Tropsch procedure entirely and hence also with the second step.
This was accomplished by adding small amounts of rhodium to the cerium oxide. Rhodium is a catalyst that enables certain chemical reactions. It has been known for some time that rhodium permits reactions with hydrogen, carbon monoxide and carbon dioxide.
Alxneit said, “The catalyst is a pivotal research topic for the production of these solar fuels.”
PhD candidate at the PSI Fangjian Lin, who works with Alxneit, emphasized “It was a huge challenge to control the extreme conditions necessary for these chemical reactions and develop a catalyst material capable of withstanding an activation process at 1500° C.” During the cooling process, for example, the extremely small rhodium islands on the material surface must not be allowed to disappear or increase in size since they are essential to the anticipated catalytic process.
The resulting fuels are either used or stored and the cyclical process begins again once the cerium oxide is heated and re-activated.
Using various standard methods of structure and gas analysis, researchers working in laboratories at the PSI and the ETH in Zurich examined the cerium-rhodium compound, explored how well the reduction of the cerium oxide works and how successful was the methane production.
Alxneit concluded, “So far, our combined process only delivers small amounts of directly usable fuel. But we have shown that our idea works and it’s taken us from the realms of science fiction to reality.”
During their experiments, researchers kept things simple by using a high performance oven at the ETH in place of solar energy.
Matthäus Rothensteiner, PhD-candidate at the PSI and the ETH Zurich whose area of responsibility included these tests explained, “In the test phase, the actual source of thermal energy is immaterial.”
Jeroen van Bokhoven, head of the PSI’s Laboratory for Catalysis and Sustainable Chemistry and Professor for Heterogeneous Catalysis at the ETH Zurich summed up saying, “These tests enabled us to gain valuable insights into the catalyst’s long-term stability. Our high performance oven allowed us to carry out 59 cycles in quick succession. Our material has comfortably survived its first endurance test.”
Having shown that their procedure is feasible in principle, researchers can now devote themselves to its optimization.
One has the impression that the Europeans are very serious on getting non-fossil sourced fuels technology into business. This effort and the one posted just last week on July 5 both show highly possible processes that could scale up and make a dent into the fossil fuel market. Not that these ideas are going to upend the petroleum industry, but much like base load electrical generation these technologies could be the basic supply of storable fuels someday, offering a fuel supply with out the wild ups and downs of the oil and gas markets.