Cheap, Non-Toxic, Super Efficient Solar Cell

In the future, solar cells can become twice as efficient by employing a few smart little nano-tricks. Researchers are currently developing the environment-friendly solar cells of the future, which will capture twice as much energy as the cells of today. The trick is to combine two different types of solar cells in order to utilize a much greater portion of the sunlight.


These are going to be the world’s most efficient and environment-friendly solar cells. There are currently solar cells that are certainly just as efficient, but they are both expensive and toxic. Furthermore, the materials in our solar cells are readily available in large quantities on Earth. That is an important point,” says Professor Bengt Svensson of the Department of Physics at the University of Oslo (UiO) and Centre for Materials Science and Nanotechnology (SMN) in Norway.

Using nanotechnology, atoms and molecules can be combined into new materials with very special properties. The goal is to utilize even more of the spectrum of sunlight than is possible at present. Ninety-nine per cent of today’s solar cells are made from silicon, which is one of the most common elements on Earth. Unfortunately, silicon solar cells only utilize 20 per cent of the sunlight. The world record is 25 per cent, but these solar cells are laced with rare materials that are also toxic. The theoretical limit is 30 per cent. The explanation for this limit is that silicon cells primarily capture the light waves from the red spectrum of sunlight. That means that most of the light waves remain unutilized.

The new solar cells will be composed of two energy-capturing layers. The first layer will still be composed of silicon cells. “The red wavelengths of sunlight generate electricity in the silicon cells in a highly efficient manner. We’ve done a great deal of work with silicon, so there is only a little more to gain.” The new trick is to add another layer on top of the silicon cells. This layer is composed of copper oxide and is supposed to capture the light waves from the blue spectrum of sunlight.


How To Recycle Carbon Dioxide

An international team of scientists led by Liang-shi Li at Indiana University (IU) has achieved a new milestone in the quest to recycle carbon dioxide in the Earth’s atmosphere into carbon-neutral fuels and others materials.


The chemists have engineered a molecule that uses light or electricity to convert the greenhouse gas carbon dioxide into carbon monoxide — a carbon-neutral fuel source — more efficiently than any other method of “carbon reduction.”

molecular leaf

If you can create an efficient enough molecule for this reaction, it will produce energy that is free and storable in the form of fuels,” said Li, associate professor in the IU Bloomington College of Arts and Sciences‘ Department of Chemistry. “This study is a major leap in that direction.”

Burning fuel — such as carbon monoxide — produces carbon dioxide and releases energy. Turning carbon dioxide back into fuel requires at least the same amount of energy. A major goal among scientists has been decreasing the excess energy needed.

This is exactly what Li’s molecule achieves: requiring the least amount of energy reported thus far to drive the formation of carbon monoxide. The molecule — a nanographene-rhenium complex connected via an organic compound known as bipyridine — triggers a highly efficient reaction that converts carbon dioxide to carbon monoxide. The ability to efficiently and exclusively create carbon monoxide is significant due to the molecule’s versatility.

Carbon monoxide is an important raw material in a lot of industrial processes,” Li said. “It’s also a way to store energy as a carbon-neutral fuel since you’re not putting any more carbon back into the atmosphere than you already removed. You’re simply re-releasing the solar power you used to make it.

The secret to the molecule’s efficiency is nanographene — a nanometer-scale piece of graphite, a common form of carbon (i.e. the black “lead” in pencils) — because the material’s dark color absorbs a large amount of sunlight.

Li said that bipyridine-metal complexes have long been studied to reduce carbon dioxide to carbon monoxide with sunlight. But these molecules can use only a tiny sliver of the light in sunlight, primarily in the ultraviolet range, which is invisible to the naked eye. In contrast, the molecule developed at IU takes advantage of the light-absorbing power of nanographene to create a reaction that uses sunlight in the wavelength up to 600 nanometers — a large portion of the visible light spectrum.

Essentially, Li said, the molecule acts as a two-part system: a nanographeneenergy collector” that absorbs energy from sunlight and an atomic rheniumengine” that produces carbon monoxide. The energy collector drives a flow of electrons to the rhenium atom, which repeatedly binds and converts the normally stable carbon dioxide to carbon monoxide.

The idea to link nanographene to the metal arose from Li’s earlier efforts to create a more efficient solar cell with the carbon-based material. “We asked ourselves: Could we cut out the middle man — solar cells — and use the light-absorbing quality of nanographene alone to drive the reaction?” he said.

Next, Li plans to make the molecule more powerful, including making it last longer and survive in a non-liquid form, since solid catalysts are easier to use in the real world.

The process is reported in the Journal of the American Chemical Society.


How To Turn Sunlight, Heat and Movement Into Electricity — All at Once

Many forms of energy surround you: sunlight, the heat in your room and even your own movements. All that energy — normally wasted — can potentially help power your portable and wearable gadgets, from biometric sensors to smart watches. Now, researchers from the University of Oulu in Finland have found that a mineral with the perovskite crystal structure has the right properties to extract energy from multiple sources at the same time.

perovskite solar panel

Perovskites are a family of minerals, many of which have shown promise for harvesting one or two types of energy at a time — but not simultaneously. One family member may be good for solar cells, with the right properties for efficiently converting solar energy into electricity. Meanwhile, another is adept at harnessing energy from changes in temperature and pressure, which can arise from motion, making them so-called pyroelectric and piezoelectric materials, respectively.

Sometimes, however, just one type of energy isn’t enough. A given form of energy isn’t always available — maybe it’s cloudy or you’re in a meeting and can’t get up to move around. Other researchers have developed devices that can harness multiple forms of energy, but they require multiple materials, adding bulk to what’s supposed to be a small and portable device.

This week in Applied Physics Letters, Yang Bai and his colleagues at the University of Oulu explain their research on a specific type of perovskite called KBNNO, which may be able to harness many forms of energy. Like all perovskites, KBNNO is a ferroelectric material, filled with tiny electric dipoles analogous to tiny compass needles in a magnet. Within the next year, Bai said, he hopes to build a prototype multi-energy-harvesting device. The fabrication process is straightforward, so commercialization could come in just a few years once researchers identify the best material. “This will push the development of the Internet of Things and smart cities, where power-consuming sensors and devices can be energy sustainable,” he said.

This kind of material would likely supplement the batteries on your devices, improving energy efficiency and reducing how often you need to recharge. One day, Bai said, multi-energy harvesting may mean you won’t have to plug in your gadgets anymore. Batteries for small devices may even become obsolete.


Paracetamol On Mars

How to produce medicine sustainably and cheaply, anywhere you want, whether in the middle of the jungle or even on Mars? Looking for a ‘mini-factory’ whereby sunlight can be captured to make chemical products? Inspired by the art of nature where leaves are able to collect enough sunlight to produce food, chemical engineers at Eindhoven University of Technology (TU/e) in Netherlands have presented such a scenario. 
Using sunlight to make chemical products has long been a dream of many a chemical engineer. The problem is that the available sunlight generates too little energy to kick off reactions. However, nature is able to do this. Antenna molecules in leaves capture energy from sunlight and collect it in the reaction centers of the leaf where enough solar energy is present for the chemical reactions that give the plant its food (photosynthesis).

Luminescent Solar Concentrator-based Photomicroreactor (LSC-PM, artificial leaf for organic synthesis), research by PhD Dario Cambie & Timothy Noël, group Micro Flow Chemistry and Process Technology, Chemical Engineering and Chemistry, TU Eindhoven. photo: TU/e, Bart van Overbeeke

Luminescent Solar Concentrator-based Photomicroreactor (LSC-PM, artificial leaf for organic synthesis), research by PhD Dario Cambie & Timothy Noël

The researchers came across relatively new materials, known as luminescent solar concentrators (LSC’s), which are able to capture sunlight in a similar way. Special light-sensitive molecules in these materials capture a large amount of the incoming light that they then convert into a specific color that is conducted to the edges via light conductivity. These LSC’s are often used in practice in combination with solar cells to boost the yield.


The results surpassed all their expectations, and not only in the lab. “Even an experiment on a cloudy day demonstrated that the chemical production was 40 percent higher than in a similar experiment without LSC material”, says research leader Noël. “We still see plenty of possibilities for improvement. We now have a powerful tool at our disposal that enables the sustainable, sunlight-based production of valuable chemical products like drugs or crop protection agents.”

For the production of drugs there is certainly a lot of potential. The chemical reactions for producing drugs currently require toxic chemicals and a lot of energy in the form of fossil fuels. By using visible light the same reactions become sustainable, cheap and, in theory, countless times faster. But Noël believes it should not have to stop there. “Using a reactor like this means you can make drugs anywhere, in principle, whether malaria drugs in the jungle or paracetamol on Mars. All you need is sunlight and this mini-factory.

The findings are described in the journal Angewandte Chemie.


Nano Device Cleans Germs from Water In 20 Minutes

In many parts of the world, the only way to make germy water safe is by boiling, which consumes precious fuel, or by putting it out in the sun in a plastic bottle so ultraviolet rays will kill the microbes. But because UV rays carry only 4 percent of the sun’s total energy, the UV method takes six to 48 hours, limiting the amount of water people can disinfect this way.

Now researchers at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have created a nanostructured device, about half the size of a postage stamp, that disinfects water much faster than the UV method by also making use of the visible part of the solar spectrum, which contains 50 percent of the sun’s energy.

clean waterA researcher holds a small, nanostructured device that uses sunlight to disinfect water. By harnessing a broad spectrum of sunlight, it works faster than devices that use only ultraviolet rays

In experiments reported today in Nature Nanotechnology, sunlight falling on the little device triggered the formation of hydrogen peroxide and other disinfecting chemicals that killed more than 99.999 percent of bacteria in just 20 minutes. When their work was done the killer chemicals quickly dissipated, leaving pure water behind.

Our device looks like a little rectangle of black glass. We just dropped it into the water and put everything under the sun, and the sun did all the work,” said Chong Liu, lead author of the report. She is a postdoctoral researcher in the laboratory of Yi Cui, a SLAC/Stanford associate professor and investigator with SIMES, the Stanford Institute for Materials and Energy Sciences at SLAC.

Under an electron microscope the surface of the device looks like a fingerprint, with many closely spaced lines. Those lines are very thin films – the researchers call them “nanoflakes” – of molybdenum disulfide that are stacked on edge, like the walls of a labyrinth, atop a rectangle of glass. In ordinary life, molybdenum disulfide is an industrial lubricant. But like many materials, it takes on entirely different properties when made in layers just a few atoms thick. In this case it becomes a photocatalyst.

By making their molybdenum disulfide walls in just the right thickness, the scientists got them to absorb the full range of visible sunlight. And by topping each tiny wall with a thin layer of copper, which also acts as a catalyst, they were able to use that sunlight to trigger exactly the reactions they wanted – reactions that produce “reactive oxygen species” like hydrogen peroxide, a commonly used disinfectant, which kill bacteria in the surrounding water.


Could Nanotechnology End Hunger?

Each year, farmers around the globe apply more than 100 million tons of fertilizer to crops, along with more than 800,000 tons of glyphosate, the most commonly used agricultural chemical and the active ingredient in Monsanto’s herbicide Roundup. It’s a quick-and-dirty approach: Plants take up less than half the phosphorus in fertilizer, leaving the rest to flow into waterways, seeding algae blooms that can release toxins and suffocate fish. An estimated 90 percent of the pesticides used on crops dissipates into the air or leaches into groundwater.

child starving

With the global population on pace to swell to more than nine billion by 2050 amid the disruptions of climate change, scientists are racing to boost food production while minimizing collateral damage to the environment. To tackle this huge problem, they’re thinking small — very small, as in nanoparticles a fraction of the diameter of a human hair. Three of the most promising developments deploy nanoparticles that boost the ability of plants to absorb nutrients in the soil, nanocapsules that release a steady supply of pesticides and nanosensors that measure and adjust moisture levels in the soil via automated irrigation systems.

It’s all part of a rise in precision agriculture, which seeks a targeted approach to the use of fertilizer, water and other resources. Recognizing the potential impact of nanotechnology, the U.S. Department of Agriculture’s National Institute of Food and Agriculture (NIFA) beefed up funding between 2011 and 2015, from $10 million to $13.5 million. India, China and Brazil are also joining the latest green revolution. Scientists led by Pratim Biswas and Ramesh Raliya at Washington University in St. Louis have harnessed fungi to synthesize nanofertilizer. When sprayed on mung bean leaves, the zinc oxide nanoparticles increase the activity of three enzymes in the plant that convert phosphorus into a more readily absorbable form. Compared to untreated plants, nanofertilized mung beans absorbed nearly 11 percent more phosphorus and showed 27 percent more growth with a 6 percent increase in yield.

Raliya and his colleagues are also developing nanoparticles that enhance plants’ absorption of sunlight and investigating how nanofertilizers fortify crops with nutrients. In a study earlier this year, they found that zinc oxide and titanium dioxide nanoparticles increased levels of the antioxidant lycopene in tomatoes by up to 113 percent. Next, they want to design nanoparticles that enhance the protein content in peanuts. Along with mung beans, peanuts are a major source of protein in many developing countries.

Others are exploring nanoparticles that protect plants against insects, fungi and weeds. The Connecticut Agricultural Experiment Station and other institutions recently began field trials that use several types of metal oxide nanoparticles on tomato, eggplant, corn, squash and sorghum plants in areas infected with fungi known to threaten crops. Researchers led by Leonardo Fernandes Fraceto, of the Institute of Science and Technology, São Paulo State University, Campus Sorocaba, are designing slow-release nanocapsules that contain two types of fungicides or herbicides to reduce the likelihood of targeted fungi and weeds developing resistance. Scientists at the University of Tehran are conducting similar research. Still others are working on nanocapsules that release plant growth hormones. Existing technology could increase average yields up to threefold in many parts of Africa.

Perovskite Solar Cells Surpass 20% Efficiency

Researchers from the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland are pushing the limits of perovskite solar cell performance by exploring the best way to grow these crystals.
Michael Graetzel and his team found that, by briefly reducing the pressure while fabricating perovskite crystals, they were able to achieve the highest performance ever measured for larger-size perovskite solar cells, reaching over 20% efficiency and matching the performance of conventional thin-film solar cells of similar sizes. This is promising news for perovskite technology that is already low cost and under industrial development. However, high performance in pervoskites does not necessarily herald the doom of silicon-based solar technology. Safety issues still need to be addressed regarding the lead content of current perovskite solar-cell prototypes in addition to determining the stability of actual devices.

peroskite solar cell

Layering perovskites on top of silicon to make hybrid solar panels may actually boost the silicon solar-cell industry. Efficiency could exceed 30%, with the theoretical limit being around 44%. The improved performance would come from harnessing more solar energy: the higher energy light would be absorbed by the perovskite top layer, while lower energy sunlight passing through the perovskite would be absorbed by the silicon layer. Graetzel is known for his transparent dye-sensitized solar cells. It turns out that the first perovskite solar cells were dye-sensitized cells where the dye was replaced by small perovskite particles. His lab’s latest perovskite prototype, roughly the size of an SD card, looks like a piece of glass that is darkened on one side by a thin film of perovskite. Unlike the transparent dye-sensitized cells, the perovskite solar cell is opaque.

The results are published in Science.


New Efficient Materials For Solar Fuel Cells

University of Texas at Arlington (UTA) chemists have developed new high-performing materials for cells that harness sunlight to split carbon dioxide and water into useable fuels like methanol and hydrogen gas. These “green fuels” can be used to power cars, home appliances or even to store energy in batteries.

solar fuel cells

Technologies that simultaneously permit us to remove greenhouse gases like carbon dioxide while harnessing and storing the energy of sunlight as fuel are at the forefront of current research,” said Krishnan Rajeshwar, UTA distinguished professor of chemistry and biochemistry and co-founder of the University’s Center of Renewable Energy, Science and Technology. “Our new material could improve the safety, efficiency and cost-effectiveness of solar fuel generation, which is not yet economically viable,” he added.

The new hybrid platform uses ultra-long carbon nanotube networks with a homogeneous coating of copper oxide nanocrystals. It demonstrates both the high electrical conductivity of carbon nanotubes and the photocathode qualities of copper oxide, efficiently converting light into the photocurrents needed for the photoelectrochemical reduction process. Morteza Khaledi, dean of the UTA College of Science, said Rajeshwar’s work is representative of the University’s commitment to addressing critical issues with global environmental impact under the Strategic Plan 2020.


Green: How To Clean Oil Sands Water Waste

Researchers have developed a process to remove contaminants from oil sands wastewater using only sunlight and nanoparticles that is more effective and inexpensive than conventional treatment methods.

Frank Gu, a professor in the Faculty of Engineering at the University of Waterloo and Canada Research Chair in Nanotechnology Engineering, is the senior researcher on the team that was the first to find that photocatalysis — a chemical reaction that involves the absorption of light by nanoparticles — can completely eliminate naphthenic acids in oil sands wastewater, and within hours. Naphthenic acids pose a threat to ecology and human health. Water in tailing ponds left to biodegrade naturally in the environment still contains these contaminants decades later.

oil sands pond

With about a billion tonnes of water stored in ponds in Alberta, removing naphthenic acids is one of the largest environmental challenges in Canada,” said Tim Leshuk, a PhD candidate in chemical engineering at Waterloo and the leader of the study . “Conventional treatments people have tried either haven’t worked, or if they have worked, they’ve been far too impractical or expensive to solve the size of the problem.  Waterloo’s technology is the first step of what looks like a very practical and green treatment method.


Electric Power: How To Increase Solar Cells Efficiency

Rice University researchers have demonstrated an efficient new way to capture the energy from sunlight and convert it into clean, renewable energy by splitting water molecules.

Hot elsplitting water Riceectrons have the potential to drive very useful chemical reactions, but they decay very rapidly, and people have struggled to harness their energy,” said lead researcher Isabell Thomann, assistant professor of nanoengineering at Rice. “For example, most of the energy losses in today’s best photovoltaic solar panels are the result of hot electrons that cool within a few trillionths of a second and release their energy as wasted heat.” Capturing these high-energy electrons before they cool could allow solar-energy providers to significantly increase their solar-to-electric power-conversion efficiencies  and reduce  the cost of solar electricity.

In the light-activated nanoparticles studied by Thomann and colleagues at Rice’s Laboratory for Nanophotonics (LANP), light is captured and converted into plasmons, waves of electrons that flow like a fluid across the metal surface of the nanoparticles. Plasmons are high-energy states that are short-lived, but researchers at Rice and elsewhere have found ways to capture plasmonic energy and convert it into useful heat or light. Plasmonic nanoparticles also offer one of the most promising means of harnessing the power of hot electrons, and LANP researchers have made progress toward that goal in several recent studies.

Thomann and her team created a system that uses the energy from hot electrons to split molecules of water into oxygen and hydrogen. That’s important because oxygen and hydrogen are the feedstocks for fuel cells, electrochemical devices that produce electricity cleanly and efficiently.

Because of the inherent inefficiencies, we wanted to find a new approach to the problem,” Thomann said. “We took an unconventional approach: Rather than driving off the hot electrons, we designed a system to carry away the electron holes. In effect, our setup acts like a sieve or a membrane. The holes can pass through, but the hot electrons cannot, so they are left available on the surface of the plasmonic nanoparticles.”

The technology, is described online in the American Chemical Society journal Nano Letters.



How To Beat Winter Blues, Jet Lag

According to the U.S. Centers for Disease Control, around one third of Americans aren’t getting enough shuteye. Jet lag, night shifts and seasonal mood disorder can disrupt sleep patterns. But psychologist Leon Lack at Australia’s Flinders University believes he has the answer. It’s called Re-Timer and uses light therapy to regulate our circadian rhythm, which tells the body when to sleep and when to wake. And though light therapy is not new, Lack says the Re-Timer‘s innovation is its portability. The breakthrough in the research was the small, light-emitting diode.
It just occurred to us that light-emitting diodes (LED), that are very small devices, very efficiently convert electricity into light and if they were mounted closer to the eyes, they would get enough light into the eyes and serve the purpose of the light therapy device.” , says Leon Lack, Co-developer of the RE-TIMER, from Flinders University.
Worn like a regular pair of spectacles, Re-Timer is adjustable and mimics the effects of sunlight using a UV-free, green light. Lack says the color choice was based on decade-long research.
That’s shown that the blue and blue/green and green area of the spectrum, those colors, are the most effective at changing the body clock timing.” Re-Timer has been a life changer for Michael Sakuma, a professor from Long Island in New York. For years Sakuma typically didn’t fall asleep until around 3 a.m. and would wake around 11 a.m. He says this late-to-bed and late-to-rise cycle severely impacted his choices. “It affected the professions I chose, because I could not choose a profession that would require me to get up at seven, 6 o’clock, the way the rest of the world seems to work. My life has been trying to move around this sleep problem and I think that the Re-Timer has really helped me in that“, he reports. Sakuma has been using his Re-Timer for about two years and says it has become part of his life: “I would like to see a day when I didn’t have to use the Re-Timer. I guess it’s because I’ve had this problem now for about 30 years, that it feels like it’s part of me and so I can’t imagine a time when I wouldn’t use it.The Re-Timer retails for around 300 U.S. dollars and with regular use of his pair, Sakuma gets to bed at a more conventional hour and catches some much-needed slumber.

Carbon NanoTubes Solar Cells Twice More Efficient

Lighter, more flexible, and cheaper than conventional solar-cell materials, carbon nanotubes (CNTs) have long shown promise for photovoltaics. But research stalled when CNTs proved to be inefficient, converting far less sunlight into power than other methods.

Now a research team led by Mark Hersam, professor of materials science and engineering at the McCormick School of Engineering, Northwestern University, has created a new type of CNT solar cell that is twice as efficient as its predecessors. It is also the first CNT solar cell to have its performance certified by the National Renewable Energy Laboratory.

solar cells
The field had been hovering around 1 percent efficiency for about a decade; it had really plateaued,.” Hersam said. “But we’ve been able to increase it to over 3 percent. It’s a significant jump
The problem is that each nanotube chirality only absorbs a narrow range of optical wavelengths,” Hersam said. “If you make a solar cell out of a single chirality carbon nanotube, you basically throw away most of the solar light.”

Hersam’s team made a mixture of polychiral, or multiple chirality, semiconducting nanotubes. This maximized the amount of photocurrent produced by absorbing a broader range of solar-spectrum wavelengths. The cells significantly absorbed near-infrared wavelengths, a range that has been inaccessible to many leading thin-film technologies.
The research is described in the article “Polychiral Semiconducting Carbon Nanotube-Fullerene Solar Cells” in the August 7 issue of Nano Letters.