Solar Cells Integrated With TriboElectric NanoGenerator Work When It Rains

Solar cells, as promising devices for converting light into electricity, have a dramatically reduced performance on rainy days Researchers from University of California  Los Angeles (UCLA) have built  an energy harvesting structure that integrates a solar cell and a triboelectric nanogenerator (TENG) device. Objective: to realize power generation from both sunlight and raindrops.

A heterojunction silicon (Si) solar cell is integrated with a TENG by a mutual electrode. Regarding the solar cell, imprinted PEDOT:PSS is used to reduce light reflection, which leads to an enhanced short-circuit current density. A single-electrode-mode water-drop TENG on the solar cell is built by combining imprinted polydimethylsiloxane (PDMS) as a triboelectric material combined with a PEDOT:PSS layer as an electrode. The increasing contact area between the imprinted PDMS and water drops greatly improves the output of the TENG.

The hybrid energy harvesting system integrated electrode configuration can combine the advantages of high current level of a solar cell and high voltage of a TENG device, promising an efficient approach to collect energy from the environment in different weather conditions.



Light-Powered Wires To Modulate Brain’s Electrical Signals

The human brain largely remains a black box: How the network of fast-moving electrical signals turns into thought, movement and disease remains poorly understood. But it is electrical, so it can be hacked—the question is finding a precise, easy way to manipulate electrical signaling between neurons.

A new University of Chicago study shows how tiny, light-powered wires could be fashioned out of silicon to provide these electrical signals. Published Feb. 19 in Nature Nanotechnology, the study offers a new avenue to shed light on—and perhaps someday treat—brain disorders.

Ten years ago, the science world was alive with speculation about a recently discovered technique called optogenetics, which would manipulate neural activity with light. The problem is that it has to be done with genetics: inserting a gene into a target cell that would make it respond to light. Other ways of modulating neurons have since been suggested, but a perfect alternative remains elusive.

A team led by Asst. Prof. Bozhi Tian built minuscule wires previously designed for solar cells. These nanowires are so small that hundreds of them could sit side by side on the edge of a sheet of paper—putting them on the same scale as the parts of cells they’re trying to communicate with.

These nanowires combine two types of silicon to create a small electrical current when struck by light. Gold, diffused by a special process onto the surface of the wire, acts as a catalyst to promote electrochemical reactions.

The rod at top right is positioned to modify electrical signaling between the neurons. The entire image is smaller than the diameter of a single human hair.

When the wire is in place and illuminated, the voltage difference between the inside and outside of the cell is slightly reduced. This lowers the barrier for the neuron to fire an electrical signal to its neighboring cells,” Tian said.


Photovoltaics: Light Absorption Enhanced by Up to 200 Percent

Sunlight reflected by solar cells is lost as unused energy. The wings of the butterfly Pachliopta aristolochiae are drilled by nanostructures (nanoholes) that help absorbing light over a wide spectrum far better than smooth surfaces. Researchers of Karlsruhe Institute of Technology (KIT) in Germany, have now succeeded in transferring these nanostructures to solar cells and, thus, enhancing their light absorption rate by up to 200 percent.

 “The butterfly studied by us is very dark black. This signifies that it perfectly absorbs sunlight for optimum heat management. Even more fascinating than its appearance are the mechanisms that help reaching the high absorption. The optimization potential when transferring these structures to photovoltaics (PV) systems was found to be much higher than expected,” says Dr. Hendrik Hölscher of KIT’s Institute of Microstructure Technology (IMT).


The scientists of the team of Hendrik Hölscher and Radwanul H. Siddique (formerly KIT, now Caltech) reproduced the butterfly’s nanostructures in the silicon absorbing layer of a thin-film solar cell. Subsequent analysis of light absorption yielded promising results: Compared to a smooth surface, the absorption rate of perpendicular incident light increases by 97% and rises continuously until it reaches 207% at an angle of incidence of 50 degrees. “This is particularly interesting under European conditions. Frequently, we have diffuse light that hardly falls on solar cells at a vertical angle,” Hendrik Hölscher says. However, this does not automatically imply that efficiency of the complete PV system is enhanced by the same factor, says Guillaume Gomard of IMT. “Also other components play a role. Hence, the 200 percent are to be considered a theoretical limit for efficiency enhancement.

The scientists have reported their results in the journal Science Advances. (DOI: 10.1126/sciadv.1700232.)


New Solar System Produces 50 Percent More Energy

A concentrating photovoltaic system (CPV) with embedded microtracking can produce over 50 percent more energy per day than standard silicon solar cells in a head-to-head competition, according to a team of engineers who field tested a prototype unit over two sunny days last fall.

Solar cells used to be expensive, but now they’re getting really cheap,” said Chris Giebink, Charles K. Etner Assistant Professor of Electrical Engineering, Penn State. “As a result, the solar cell is no longer the dominant cost of the energy it produces. The majority of the cost increasingly lies in everything else — the inverter, installation labor, permitting fees, etc. — all the stuff we used to neglect.

This changing economic landscape has put a premium on high efficiency. In contrast to silicon solar panels, which currently dominate the market at 15 to 20 percent efficiency, concentrating photovoltaics focus sunlight onto smaller, but much more efficient solar cells like those used on satellites, to enable overall efficiencies of 35 to 40 percent. Current CPV systems are large — the size of billboards — and have to rotate to track the sun during the day. These systems work well in open fields with abundant space and lots of direct sun.

What we’re trying to do is create a high-efficiency CPV system in the form factor of a traditional silicon solar panel,” said Giebink.


SuperPowerful Tiny Device Converts Light Into Electricity

In today’s increasingly powerful electronics, tiny materials are a must as manufacturers seek to increase performance without adding bulk. Smaller also is better for optoelectronic devices — like camera sensors or solar cells —which collect light and convert it to electrical energy. Think, for example, about reducing the size and weight of a series of solar panels, producing a higher-quality photo in low lighting conditions, or even transmitting data more quickly.

However, two major challenges have stood in the way: First, shrinking the size of conventionally used “amorphousthin-film materials also reduces their quality. And second, when ultrathin materials become too thin, they are almost transparent — and actually lose some ability to gather or absorb light.

Now, in a nanoscale photodetector that combines both a unique fabrication method and light-trapping structures, a team of engineers from the University at Buffalo (UB) and the University of Wisconsin-Madison (UW-Madison) has overcome both of those obstacles. The researchers — electrical engineers Qiaoqiang Gan at UB, and Zhenqiang (Jack) Ma and Zongfu Yu at UW-Madison — described their device, a single-crystalline germanium nanomembrane photodetector on a nanocavity substrate, in the July 7, 2017, issue of the journal Science Advances.

This image shows the different layers of the nanoscale photodetector, including germanium (red) in between layers of gold or aluminum (yellow) and aluminum oxide (purple). The bottom layer is a silver substrate

We’ve created an exceptionally small and extraordinarily powerful device that converts light into energy,” says Gan, associate professor of electrical engineering in UB’s School of Engineering and Applied Sciences, and one of the paper’s lead authors. “The potential applications are exciting because it could be used to produce everything from more efficient solar panels to more powerful optical fibers.”

The idea, basically, is you want to use a very thin material to realize the same function of devices in which you need to use a very thick material,” says Ma, the Lynn H. Matthias Professor and Vilas Distinguished Achievement Professor in electrical and computer engineering at UW-Madison, also a lead author. Nanocavities are made up of an orderly series of tiny, interconnected molecules that essentially reflect, or circulate, light.

The new device is an advancement of Gan’s work developing nanocavities that increase the amount of light that thin semiconducting materials like germanium can absorb. It consists of nanocavities sandwiched between a top layer of ultrathin single-crystal germanium and a bottom, reflecting layer of silver.


Sion, The Solar-Powered Car

What has room for 6 passengers, an all-electric range of up to 155 miles (250 kilometers), and a body covered in solar panels that can add as many as 18 miles (30 kilometers) of driving a day from sunlight? That would be the Sono Motors Sion, an innovative solar-powered car from a team of German entrepreneurs that is scheduled to have its world debut on July 27 (2017).

The Sion project was able to move forward thanks to an Indiegogo crowdfunding campaign last year that raised over a half million dollars. More than 1,000 people have participated so far.

The car will have two versions. The Urban comes with a 14.4 kilowatt-hour battery pack. It has a range of about 75 miles (121 kilometers) and will cost $13,200. The Extender version has a 30 kilowatt-hour battery and a range of 155 miles (250 kilometers). Its target price is $17,600. Neither price includes the battery. Like the Renault Zoe, customers will either buy the battery separately or lease it. The leasing option gives owners the flexibility to upgrade the battery later as improvements in battery technology become available.

The hood, roof, and rear hatch of the Sion are covered with monocrystalline silicon cells that are 21% efficient. On a sunny day, they can generate enough electricity to add 18 miles of range. The solar cells are 8 millimeters thick and embedded in a polycarbonate layer that is shatterproof, weather resistant, and light in weight. The Sion can also be 80% charged using an AC outlet in about 30 minutes, according to company claims. No DC charging option is available. The car also comes with an outlet that can power electronic devices.

Inside, all the seats of the 5 door hatchback fold flat, offering multiple configurations for carrying passengers and cargo. There is a 10 inch center display and smartphone connectivity via WiFi or Bluetooth. The ventilation system is called breSono and incorporates a dollop of moss, which is said to act as a natural filter when an electrical charge is applied.

The company will offer an online maintenance and repair system it calls reSono. It allows owners to order parts online and comes with a video that shows them how to install the parts when they arrive.  Or they can take the car and the parts to any local auto repair shop facility to get them installed.


Perovskite Solar Cells Conversion Efficiency Rises Up To 20%

A new low-temperature solution printing technique allows fabrication of high-efficiency perovskite solar cells with large crystals intended to minimize current-robbing grain boundaries. The meniscus-assisted solution printing (MASP) technique boosts power conversion efficiencies to nearly 20 percent by controlling crystal size and orientation.

The process, which uses parallel plates to create a meniscus of ink containing the metal halide perovskite precursors, could be scaled up to rapidly generate large areas of dense crystalline film on a variety of substrates, including flexible polymers. Operating parameters for the fabrication process were chosen by using a detailed kinetics study of perovskite crystals observed throughout their formation and growth cycle.

We used a meniscus-assisted solution printing technique at low temperature to craft high quality perovskite films with much improved optoelectronic performance,” said Zhiqun Lin, a professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. “We began by developing a detailed understanding of crystal growth kinetics that allowed us to know how the preparative parameters should be tuned to optimize fabrication of the films.”

The new technique is reported in the journal Nature Communications.


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.


Printable solar cells

A University of Toronto (U of T) Engineering innovation could make building printing cells as easy and inexpensive as printing a newspaper. Dr. Hairen Tan and his team have cleared a critical manufacturing hurdle in the development of a relatively new class of solar devices called perovskite solar cells. This alternative solar technology could lead to low-cost, printable solar panels capable of turning nearly any surface into a power generator.

Printable Perovskite SolarCell

Economies of scale have greatly reduced the cost of silicon manufacturing,” says University Professor Ted Sargent (ECE), an expert in emerging solar technologies and the Canada Research Chair in Nanotechnology and senior author on the paper. “Perovskite solar cells can enable us to use techniques already established in the printing industry to produce solar cells at very low cost. Potentially, perovskites and silicon cells can be married to improve efficiency further, but only with advances in low-temperature processes.”

Today, virtually all commercial solar cells are made from thin slices of crystalline silicon which must be processed to a very high purity. It’s an energy-intensive process, requiring temperatures higher than 1,000 degrees Celsius and large amounts of hazardous solvents.

In contrast, perovskite solar cells depend on a layer of tiny crystals — each about 1,000 times smaller than the width of a human hair — made of low-cost, light-sensitive materials. Because the perovskite raw materials can be mixed into a liquid to form a kind of ‘solar ink’, they could be printed onto glass, plastic or other materials using a simple inkjet process.


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.


Solar Panels Reach 36.4 Percent Efficiency

Swiss start-up Insolight says its solar panels double the yield achieved by other sun-powered technology. In independent tests the panels reached an efficiency of 36.4 percent.


Traditionally the market sits at around 18 percent and we can double this. Therefore we can double the return on investment for the final client….Our key innovation is that you do not need to rotate the panel in order to follow the sun. We can follow the sun in a flat manner, like any other solar panel, which makes it that our panel can be installed on standard rooftops, with standard mounting technology,” says Florian Gerlich Co-Founder of Insolight company.

Tiny square super cells capture all of the sun’s rays, underneath round lenses, using a patented microtracking system. “Why micro? Why tracking? Micro is a really really small movement that is encapsulated into the solar panel and tracking is to track the sun to concentrate the light into our really tiny solar cell,” comments Noe Bory from Insolight.  An injection-moulded transparent plate moves one centimetre throughout the day, a small sensor detecting the sun’s position.

“As you see here the small squares spread out over the whole surface and under each of these lenses there is a small solar cell. It’s a bit like the lenses that you’re using in your reading lenses or your reading glasses. It’s the same technology, it’s just a particular shape in order to be able to follow the sun from morning to the evening,” adds Florian Gerlich.

The panels may be more expensive to buy than current technology. But Insolight says energy prices will be slashed from 14 US cents per kilowatt hour to 9 cents. A large bed of panels will be tested in Lausanne this summer. Insolight says the system could be market-ready next year.

Breakthrough In The BioMedical Industry

Polyhedral boranes, or clusters of boron atoms bound to hydrogen atoms, are transforming the biomedical industry. These manmade materials have become the basis for the creation of cancer therapies, enhanced drug delivery and new contrast agents needed for radioimaging and diagnosis. Now, a researcher at the University of Missouri has discovered an entirely new class of materials based on boranes that might have widespread potential applications, including improved diagnostic tools for cancer and other diseases as well as low-cost solar energy cells.

Mark Lee Jr., an assistant professor of chemistry in the MU College of Arts and Science, discovered the new class of hybrid nanomolecules by combining boranes with carbon and hydrogen. Boranes are chemically stable and have been tested at extreme heat of up to 900 degrees Celsius or 1,652 degrees Fahrenheit. It is the thermodynamic stability these molecules exhibit that make them non-toxic and attractive to the biomedical, personal computer and alternative energy industries.
Polyhedral boranes

Despite their stability, we discovered that boranes react with aromatic hydrocarbons at mildly elevated temperatures, replacing many of the hydrogen atoms with rings of carbon,” Lee said. “Polyhedral boranes are incredibly inert, and it is their reaction with aromatic hydrocarbons like benzene that will make them more useful.”

Lee also showed that the attached hydrocarbons communicate with the borane core. “The result is that these new materials are highly fluorescent in solution,” Lee said. “Fluorescence can be used in applications such as bio-imaging agents and organic light-emitting diodes like those in phones or television screens. Solar cells and other alternative energy sources also use fluorescence, so there are many practical uses for these new materials.
The findings have been recently published in the international journal Angewandte Chemie.