Posts belonging to Category electronics

How To Spray Solar Cells

A new study out of St. Mary’s College of Maryland puts us closer to do-it-yourself spray-on solar cell technology—promising third-generation solar cells utilizing a nanocrystal ink deposition that could make traditional expensive silicon-based solar panels a thing of the past.

In a 2014 study, published in the journal Physical Chemistry Chemical Physics, St. Mary’s College of Maryland energy expert Professor Troy Townsend introduced the first fully solution-processed all-inorganic photovoltaic technology.

spray-on solar cells
While progress on organic thin-film photovoltaics is rapidly growing, inorganic devices still hold the record for highest efficiencies which is in part due to their broad spectral absorption and excellent electronic properties. Considering the recorded higher efficiencies and lower cost per watt compared to organic devices, combined with the enhanced thermal and photo stability of bulk-scale inorganic materials, Townsend, in his 2014 study, focused on an all-inorganic based structure for fabrication of a top to bottom fully solution-based solar cell.

A major disadvantage compared to organics, however, is that inorganic materials are difficult to deposit from solution. To overcome this, Townsend synthesized materials on the nanoscale. Inorganic nanocrystals encased in an organic ligand shell are soluble in organic solvents and can be deposited from solution (i.e., spin-, dip-, spray-coat) whereas traditional inorganic materials require a high temperature vacuum chamber. The solar devices are fabricated from nanoscale particle inks of the light absorbing layers, cadmium telluride/cadmium selenide, and metallic inks above and below. This way, the entire electronic device can be built on non-conductive glass substrates using equipment you can find in your kitchen.

When you spray on these nanocrystals, you have to heat them to make them work,” explained Townsend, “but you can’t just heat the crystals by themselves, you have to add a sintering agent and that, for the last 40 years, has been cadmium chloride, a toxic salt used in commercial thin-film devices. No one has tested non-toxic alternatives for nanoscale ink devices, and we wanted to explore the mechanism of the sintering process to be able to implement safer salts.”


“Chewing gum” Material 3 Times Stronger Than Steel

Creating futuristic, next generation materials called ‘metallic glass’ that are ultra-strong and ultra-flexible will become easier and cheaper, based on UNSW Australia research that can predict for the first time which combinations of metals will best form these useful materials.

Just like something from science fiction – think of the Liquid-Metal robot assassin in the Terminator films – these materials behave more like glass or plastic than metal.

While still being metals, they become as malleable as chewing gum when heated and can be easily moulded or blown like glass. They are also three times stronger and harder than ordinary metals, on average, and are among the toughest materials known.


liquid_terminatorThe Terminator‘s Liquid Metal Man: While still being metals, they become as malleable as chewing gum when heated and can be easily moulded or blown like glass.

They have been described as the most significant development in materials science since the discovery of plastics more than 50 years ago,” says study author, UNSW’s Dr Kevin Laws.

Most metals are crystalline when solid, with their atoms arranged in a highly organised and regular manner. Metallic glass alloys, however, have a highly disordered structure, with the atoms arranged in a non-regular way.


Electronic Circuits Mimic The Human Brain

Researchers of the MESA+ Institute for Nanotechnology and the CTIT Institute for ICT Research at the University of Twente in The Netherlands have demonstrated working electronic circuits that have been produced in a radically new way, using methods that resemble Darwinian evolution. The size of these circuits is comparable to the size of their conventional counterparts, but they are much closer to natural networks like the human brain. The findings promise a new generation of powerful, energy-efficient electronics, and have been published in the journal Nature Nanotechnology. The approach of the researchers at the University of Twente is based on methods that resemble those found in Nature. They have used networks of gold nanoparticles for the execution of essential computational tasks. Contrary to conventional electronics, they have moved away from designed circuits. By using ‘designless‘ systems, costly design mistakes are avoided. The computational power of their networks is enabled by applying artificial evolution. This evolution takes less than an hour, rather than millions of years. By applying electrical signals, one and the same network can be configured into 16 different logical gates. The evolutionary approach works around – or can even take advantage of – possible material defects that can be fatal in conventional electronics.

One of the greatest successes of the 20th century has been the development of digital computers. During the last decades these computers have become more and more powerful by integrating ever smaller components on silicon chips. However, it is becoming increasingly hard and extremely expensive to continue this miniaturisation. Current transistors consist of only a handful of atoms. It is a major challenge to produce chips in which the millions of transistors have the same characteristics, and thus to make the chips operate properly. Another drawback is that their energy consumption is reaching unacceptable levels. It is obvious that one has to look for alternative directions, and it is interesting to see what we can learn from nature. Natural evolution has led to powerful ‘computers’ like the human brain, which can solve complex problems in an energy-efficient way. Nature exploits complex networks that can execute many tasks in parallel.


How To Make Objects Invisible

Scientists at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley have devised an ultra-thin invisibilityskincloak that can conform to the shape of an object and conceal it from detection with visible light. Although this cloak is only microscopic in size, the principles behind the technology should enable it to be scaled-up to conceal macroscopic items as well.

Working with brick-like blocks of gold nanoantennas, the Berkeley researchers fashioned a “skin cloak” barely 80 nanometers in thickness, that was wrapped around a three-dimensional object about the size of a few biological cells and arbitrarily shaped with multiple bumps and dents. The surface of the skin cloak was meta-engineered to reroute reflected light waves so that the object was rendered invisible to optical detection when the cloak is activated.

Invisible objectsA 3D illustration of a metasurface skin cloak made from an ultrathin layer of nanoantennas (gold blocks) covering an arbitrarily shaped object. Light reflects off the cloak (red arrows) as if it were reflecting off a flat mirror

This is the first time a 3D object of arbitrary shape has been cloaked from visible light,” said Xiang Zhang, director of Berkeley Lab’s Materials Sciences Division and a world authority on metamaterials – artificial nanostructures engineered with electromagnetic properties not found in nature. “Our ultra-thin cloak now looks like a coat. It is easy to design and implement, and is potentially scalable for hiding macroscopic objects.”


Hybrid Solar Cells 20% More Efficient

Scientists have developed a new hybrid, solar-energy system that harnesses the full spectrum of the sun’s radiation by pairing a photovoltaic cell with polymer films. The films convert the light that goes unused by the solar cell into heat and then converts the heat into electricity. The device produces a voltage more than five times higher than other hybrid systems.

Solar cells today are getting better at converting sunlight to electricity, but commercial panels still harvest only part of the radiation they’re exposed to. Scientists are working to change this using various methods. One approach is to hybridize solar cells with different materials to capture more of the sun’s energy. Professor Eunkyoung Kim, from Seoul’s Yonsei University (Korea), and colleagues turned to a clear, conductive polymer known as PEDOT to try to accomplish this.

hybrid solar cells

A display changes colors, powered solely by a new hybrid solar-energy device

The researchers layered a dye-sensitized solar cell on top of a PEDOT film, which heats up in response to light. Below that, they added a pyroelectric thin film and a thermoelectric device, both of which convert heat into electricity. The efficiency of all components working together was more than 20 percent higher than the solar cell alone. With that boost, the system could operate an LED lamp and an electrochromic display.

A report has been published in the journal ACS Nano.


Car, Boat, Airplane: Bye Bye Sickness

The misery of motion sickness could be ended within five to ten years thanks to a new treatment being developed by scientists. The cause of motion sickness is still a mystery but a popular theory among scientists says it is to do with confusing messages received by our brains from both our ears and eyes, when we are moving. It is a very common complaint and has the potential to affect all of us, meaning we get a bit queasy on boats or rollercoasters. However, around three in ten people experience hard-to-bear motion sickness symptoms, such as dizziness, severe nausea, cold sweats, and more.

Research from Imperial College London, published today (4 September) in the journal Neurology, shows that a mild electrical current applied to the scalp can dampen responses in an area of the brain that is responsible for processing motion signals. Doing this helps the brain reduce the impact of the confusing inputs it is receiving and so prevents the problem that causes the symptoms of motion sickness. This technique offers a safe and effective intervention that is likely to be available for anyone to buy, in the future.


We are confident that within five to ten years people will be able to walk into the chemist and buy an anti-seasickness device. It may be something like a tens machine that is used for back pain”, said Dr Qadeer Arshad from the Department of Medicine at Imperial College London who led the research. “We hope it might even integrate with a mobile phone, which would be able to deliver the small amount of electricity required via the headphone jack. In either case, you would temporarily attach small electrodes to your scalp before travelling – on a cross channel ferry, for example.


Solar Cells Collect 30 Times More From Sun’s Photons

By combining designer quantum dot light-emitters with spectrally matched photonic mirrors, a team of scientists with Berkeley Lab and the University of Illinois created solar cells that collect blue photons at 30 times the concentration of conventional solar cells, the highest luminescent concentration factor ever recorded. This breakthrough paves the way for the future development of low-cost solar cells that efficiently utilize the high-energy part of the solar spectrum.


 Solar (or photovoltaic) cells convert the sun’s energy into electricity. Whether they’re adorning your calculator or orbiting our planet on satellites, they rely on the the photoelectric effect: the ability of matter to emit electrons when a light is shone on it. Silicon is what is known as a semi-conductor, meaning that it shares some of the properties of metals and some of those of an electrical insulator, making it a key ingredient in solar cells. Let’s take a closer look at what happens when the sun shines onto a solar cell.
Sunlight is composed of miniscule particles called photons, which radiate from the sun. As these hit the silicon atoms of the solar cell, they transfer their energy to loose electrons, knocking them clean off the atoms. The photons could be compared to the white ball in a game of pool, which passes on its energy to the coloured balls it strikes. Freeing up electrons is however only half the work of a solar cell: it then needs to herd these stray electrons into an electric current. This involves creating an electrical imbalance within the cell, which acts a bit like a slope down which the electrons will flow in the same direction. Creating this imbalance is made possible by the internal organisation of silicon.


Nanotube-based Transistor For Nanocomputers

Individual transistors made from carbon nanotubes are faster and more energy efficient than those made from other materials. Going from a single transistor to an integrated circuit full of transistors, however, is a giant leap.

carbon nanotube integrated circuits

A single microprocessor has a billion transistors in it,” said Northwestern Engineering’s Mark Hersam. “All billion of them work. And not only do they work, but they work reliably for years or even decades.

When trying to make the leap from an individual, nanotube-based transistor to wafer-scale integrated circuits, many research teams, including Hersam’s, have met challenges. For one, the process is incredibly expensive, often requiring billion-dollar cleanrooms to keep the delicate nano-sized components safe from the potentially damaging effects of air, water, and dust. Researchers have also struggled to create a carbon nanotube-based integrated circuit in which the transistors are spatially uniform across the material, which is needed for the overall system to work.

Now Hersam and his team have found a key to solving all these issues. The secret lies in newly developed encapsulation layers that protect carbon nanotubes from environmental degradation.

Supported by the Office of Naval Research and the National Science Foundation, the research appears online in Nature Nanotechology on September 7. Tobin J. Marks,  professor of materials science and engineering in the McCormick School of Engineering, coauthored the paper. Michael Geier, a graduate student in Hersam’s lab, was first author. “One of the realities of a nanomaterial, such as a carbon nanotube, is that essentially all of its atoms are on the surface,” said Hersam, the Walter P. Murphy Professor of Materials Science and Engineering. “So anything that touches the surface of these materials can influence their properties. If we made a series of transistors and left them out in the air, water and oxygen would stick to the surface of the nanotubes, degrading them over time. We thought that adding a protective encapsulation layer could arrest this degradation process to achieve substantially longer lifetimes.

Hersam compares his solution to one currently used for organic light-emitting diodes (LEDs), which experienced similar problems after they were first realized. Many people assumed that organic LEDs would have no future because they degraded in air. After researchers developed an encapsulation layer for the material, organic LEDs are now used in many commercial applications, including displays for smartphones, car radios, televisions, and digital cameras. Made from polymers and inorganic oxides, Hersam’s encapsulation layer is based on the same idea but tailored for carbon nanotubes.

To demonstrate proof of concept, Hersam developed nanotube-based static random-access memory (SRAM) circuits. SRAM is a key component of all microprocessors, often making up as much as 85 percent of the transistors in the central-processing unit in a common computer. To create the encapsulated carbon nanotubes, the team first deposited the carbon nanotubes from a solution previously developed in Hersam’s lab. Then they coated the tubes with their encapsulation layers.

Using the encapsulated carbon nanotubes, Hersam’s team successfully designed and fabricated arrays of working SRAM circuits. Not only did the encapsulation layers protect the sensitive device from the environment, but they improved spatial uniformity among individual transistors across the wafer. While Hersam’s integrated circuits demonstrated a long lifetime, transistors that were deposited from the same solution but not coated degraded within hours.

After we’ve made the devices, we can leave them out in air with no further precautions,” Hersam said. “We don’t need to put them in a vacuum chamber or controlled environment. Other researchers have made similar devices but immediately had to put them in a vacuum chamber or inert environment to keep them stable. That’s obviously not going to work in a real-world situation.”


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.



Water-powered MotorBike

Ricardo Azevedo was frustrated with the ever increasing price of gas. So he used his skills as a mechanic and took some tips from his son’s chemistry book to build a water powered motorcycle.

hydrogen motobike

I still haven’t developed everything is it capable of, but I did some tests and in certain settings it can go 500 kilometres (310 miles) using one litre of water,” says Azevedo.
An electrical current is fed into a canister of water which breaks the liquid down into hydrogen and oxygen using the process of electrolysis. The hydrogen gas is then used to power the engine. Research into hydrogen combustion power has increased dramatically over the past decade and while the chemical process used to generate energy from water is well understood, its market potential is curbed until a way to safely contain and use the highly flammable hydrogen gas is developed. Azevedo says the environmental benefits of using his water powered bike or other hydrogen energy sources far outweigh the risks involved.  “It does not cause any damage to the environment, on the contrary as it will go on to replace fossil fuels and reduce carbon monoxide emissions,” he adds.
Azevedo is continuing to tinker and improve the efficiency of his bike. He says getting fuel from a river beats stopping at a gas station any day of the week.


After Graphene, New 2D Materials To Play With

Dozens of new two-dimensional materials similar to graphene are now available, thanks to research from the University of Manchester (U.K.) scientists. These 2D crystals are capable of delivering designer materials with revolutionary new properties. The problem has been that the vast majority of these atomically thin 2D crystals are unstable in air, so react and decompose before their properties can be determined and their potential applications investigated.  By protecting the new reactive crystals with more stable 2D materials, such as , via computer control in a specially designed inert gas chamber environments, these materials can be successfully isolated to a single atomic layer for the first time.
2D materials

The team created devices to stablise 2D materials

Combining a range of 2D materials in thin stacks give scientists the opportunity to control the properties of the materials, which can allow ‘materials-to-order’ to meet the demands of industry.  High-frequency electronics for satellite communications, and light weight batteries for mobile energy storage are just two of the application areas that could benefit from this research. The breakthrough could allow for many more atomically thin materials to be studied separately as well as serve as building blocks for multilayer devices with such tailored properties.

The team, led by Dr Roman Gorbachev, used their unique fabrication method on two particular two-dimensional crystals that have generated intense scientific interest in the past 12 months but are unstable in air: black phosphorus and niobium diselenide. The technique the team have pioneered allows the unique characteristics and excellent electronic properties of these air-sensitive 2D crystals to be revealed for the first time.

The isolation of graphene in 2004 by a University of Manchester team lead by Sir Andre Geim and Sir Kostya Novoselov led to the discovery of a range of 2D materials, each with specific properties and qualities. Dr Gorbachev said: “This is an important breakthrough in the area of 2D materials research, as it allows us to dramatically increase the variety of materials that we can experiment with using our expanding 2D crystal toolbox”. The more materials we have to play with, the greater potential there is for creating applications that could revolutionise the way we live.” Sir Andre Geim added.

Writing in NanoLetters, the University of Manchester team demonstrate how tailored fabrication methods can make these previously inaccessible materials useful.


Black Phosphorus Instead Of Silicon

Silicon Valley in Northern California got its nickname from the multitude of computer chip manufacturers that sprung up in the surrounding area in the 1980’s.  Despite its ubiquity as a chip building material, silicon may be facing some competition from a new version of an old substance.

Researchers working at the Institute for Basic Science (IBS) Center for Integrated Nanostructure Physics at Sungkyunkwan University (SKKU) in South Korea, led in part by Director Young Hee Lee, have created a high performance transistor using black phosphorus (BP) which has revealed some fascinating results.

Transistors are made up of materials with semiconducting properties, which come in two varieties: n-type (excess electrons) and p-type (excess holes). With the BP crystal, researchers have discovered that they can change its thickness and/or the contact metals and that will determine if it is high performance n-type, p-type, or ambipolar (function as both n- or p-type) material.

Atomic structure of black phosphorus monolayer

Sibplicon has to be extrinsically doped (inserting another element into its crystal structure) to make it n-type or p-type in order for it to work in a semiconductor chip.   The BP crystals can operate as both n-type and p-type or something in between, but don’t require extrinsic doping.  This means that instead of having to fabricate a silicon-arsenic crystal sandwiched between silicon-boron crystals, a transistor can have a single, lightweight, pure black phosphorus logic chip — no doping required.

Additionally, changing the metals used to connect the chip to the circuit has an influence on whether BP will be n- or p-type.  Instead of doping to make an n- and p-type material, both n- and p-type BP can be put all together on one chip just by changing its thickness and the contact metal used.