Green Solar Panels And Other Colors

Researchers from AMOLF, the University of Amsterdam (UvA) and the Energy Research Centre of the Netherlands (ECN) have developed a technology to create efficient bright green colored solar panels. Arrays of silicon nanoparticles integrated in the front module glass of a silicon heterojunction solar cell scatter a narrow band of the solar spectrum and create a green appearance for a wide range of angles. The remainder of the solar spectrum is efficiently coupled into the solar cell. The current generated by the solar panel is only  reduced by 10%. The realization of efficient colorful solar panels is an important step for the integration of solar panels into the built environment and landscape.
research has much focused on maximizing the electricity yield obtained from solar panels: nowadays, commercial panels have a maximum conversion efficiency from sunlight into electricity of around 22%. To reach such high efficiency, silicon solar cells have been equipped with a textured surface with an antireflection layer to absorb as much light as possible. This creates a dark blue or black appearance of the solar panels.

To create the colored solar panels the researchers have used the effect of Mie scattering, the resonant backscattering of light with a particular color by nanoparticles. They integrated dense arrays of silicon nanocylinders with a diameter of 100 nm in the top module cover slide of a high-efficiency silicon heterojunction solar cell. Due to the resonant nature of the light scattering effect, only the green part of the spectrum is reflected; the other colors are fully coupled into the solar cell. The current generated by the mini solar panel (0,7 x 0,7 cm2)  is only reduced by 10%. The solar panel appears green over a broad range of angles up to 75 degrees. The nanoparticles are fabricated using soft-imprint lithography, a technique that can readily be scaled up to large-area fabrication.
The light scattering effect due to Mie resonances is easily controllable: by changing the size of the nanoparticles the wavelength of the resonant light scattering can be tuned. Following this principle the researchers are now working to realize solar cells in other colors, and on a combination of different colors to create solar panels with a white appearance. For the large-scale application of solar panels, it is essential that their color can be tailored.

The new design was published online in the journal Applied Physics Letters.


Nano-LED 1000 Times More Efficient

The electronic data connections within and between microchips are increasingly becoming a bottleneck in the exponential growth of data traffic worldwide. Optical connections are the obvious successors but optical data transmission requires an adequate nanoscale light source, and this has been lacking. Scientists at Eindhoven University of Technology (TU/e) now have created a light source that has the right characteristics: a nano-LED that is 1000 times more efficient than its predecessors, and is capable of handling gigabits per second data speeds.

NANO LEDWith electrical cables reaching their limits, optical connections like fiberglass are increasingly becoming the standard for data traffic. Over longer distances almost all data transmission is optical. Within computer systems and microchips, too, the growth of data traffic is exponential, but that traffic is still electronic, and this is increasingly becoming a bottleneck. Since these connections (‘interconnects’) account for the majority of the energy consumed by chips, many scientists around the world are working on enabling optical (photonic) interconnects. Crucial to this is the light source that converts the data into light signals which must be small enough to fit into the microscopic structures of microchips. At the same time, the output capacity and efficiency have to be good. Especially the efficiency is a challenge, as small light sources, powered by nano– or microwatts, have always performed very inefficiently to date.
The researchers in Eindhoven believe that their nano-LED is a viable solution that will take the brake off the growth of data traffic on chips. However, they are cautious about the prospects. The development is not yet at the stage where it can be exploited by the industry and the production technology that is needed still has to get off the ground.
The findings are reported in the online journal Nature Communications.


How To Manipulate Light

Electrons are so 20th century. In the 21st century, photonic devices, which use light to transport large amounts of information quickly, will enhance or even replace the electronic devices that are ubiquitous in our lives today. But there’s a step needed before optical connections can be integrated into telecommunications systems and computers: researchers need to make it easier to manipulate light at the nanoscale.

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have done just that, designing the first on-chip metamaterial with a refractive index of zero, meaning that the phase of light can travel infinitely fast.

This new metamaterial was developed in the lab of Eric Mazur, the Balkanski Professor of Physics and Applied Physics and Area Dean for Applied Physics at SEAS, and is described in the journal Nature Photonics.

manipulated light

New zero-index material made of silicon pillar arrays embedded in a polymer matrix and clad in gold film creates a constant phase of light, which stretches out in infinitely long wavelengths

Light doesn’t typically like to be squeezed or manipulated but this metamaterial permits you to manipulate light from one chip to another, to squeeze, bend, twist and reduce diameter of a beam from the macroscale to the nanoscale,” said Mazur. “It’s a remarkable new way to manipulate light.”

Although this infinitely high velocity sounds like it breaks the rule of relativity, it doesn’t. Nothing in the universe travels faster than light carrying information — Einstein is still right about that. But light has another speed, measured by how fast the crests of a wavelength move, known as phase velocity. This speed of light increases or decreases depending on the material it’s moving through.

When light passes through water, for example, its phase velocity is reduced as its wavelengths get squished together. Once it exits the water, its phase velocity increases again as its wavelength elongates. How much the crests of a light wave slow down in a material is expressed as a ratio called the refraction index — the higher the index, the more the material interferes with the propagation of the wave crests of light. Water, for example, has a refraction index of about 1.3.

When the refraction index is reduced to zero, really weird and interesting things start to happen.


Super-Efficient Light-Based Nanocomputers

Stanford electrical engineer Jelena Vuckovic wants to make computers faster and more efficient by reinventing how they send data back and forth between chips, where the work is done.

In computers today, data is pushed through wires as a stream of electrons. That takes a lot of power, which helps explain why laptops get so warm.

Several years ago, my colleague David Miller carefully analyzed power consumption in computers, and the results were striking,” said Vuckovic, referring to David Miller, the W.M. Keck Foundation Professor of Electrical Engineering. “Up to 80 percent of the microprocessor power is consumed by sending data over the wires – so-called interconnects.”

In a Nature Photonics article whose lead author is Stanford graduate student Alexander Piggott, Vuckovic, a professor of electrical engineering, and her team explain a process that could revolutionize computing by making it practical to use light instead of electricity to carry data inside computers.

infrared lightIn essence, the Stanford engineers want to miniaturize the proven technology of the Internet, which moves data by beaming photons of light through fiber optic threads

Optical transport uses far less energy than sending electrons through wires,” Piggott said. “For chip-scale links, light can carry more than 20 times as much data.”

Theoretically, this is doable because silicon is transparent to infrared light – the way glass is transparent to visible light. So wires could be replaced by optical interconnects: silicon structures designed to carry infrared light.

How to “Grow” Billions Of Light Dots Directly On Chips

Researchers from the University of California, Santa Barbara (UCSB), in collaboration with the DARPA, succeeded to grow lasers directly on microchips, a breaktrhrough that will enable the mass-production of inexpensive and robust microsystems that exceed the performance capabilities of current technologies.

Defense systems for instance, such as radar, communications, imaging and sensing payloads rely on a wide variety of microsystems devices. These diverse devices typically require particular substrates or base materials and different processing technologies specific to each application, preventing the integration of such devices into a single fabrication process. Integration of these technologies, historically, has required combining one microchip with another, which introduces significant bandwidth and latency limitations as compared to microsystems integrated on a single chip. Although many photonic components can now be fabricated directly on silicon, realizing an efficient laser source on silicon has proven to be very difficult.
Now, the engineers at UCSB showed it was possible to “grow” or deposit successive layers of indium arsenide material directly on silicon wafers to form billions of light-emitting dots known as “quantum dots.” This method of integrating electronic and photonic circuits on a common silicon substrate promises to eliminate wafer bonding, and has application in numerous military and civilian electronics where size, weight, power and packaging/assembly costs are critical.
laser on chipsDARPA’s Electronic-Photonic Heterogeneous Integration (E-PHI) program has successfully integrated billions of light-emitting dots on silicon to create an efficient silicon-based laser. The Defense Advanced Research Projects Agency (DARPA) is an agency of the United States Department of Defense responsible for the development of new technologies for use by the military.
This method of integrating electronic and photonic circuits on a common silicon substrate promises to eliminate wafer bonding, and has application in numerous military and civilian electronics where size, weight, power and packaging/assembly costs are critical“.“It is anticipated that these E-PHI demonstrator microsystems will provide considerable performance improvement and size reduction versus state-of-the-art technologies,” said Josh Conway, DARPA program manager for E-PHI. “Not only can lasers be easily integrated onto silicon, but other components can as well, paving the way for advanced photonic integrated circuits with far more functionality than can be achieved today.


Computer: Nano Optical Cables To Replace Copper

Electrical engineers design nano-optical cables that could replace copper wiring on computer chips. The invention of fibre optics revolutionized the way we share information, allowing us to transmit data at volumes and speeds we’d only previously dreamed of. Now, electrical engineering researchers at the University of Alberta are breaking another barrier, designing nano-optical cables small enough to replace the copper wiring on computer chips. This could result in radical increases in computing speeds and reduced energy use by electronic devices. A new step towards the nanocomputer era.

We’re already transmitting data from continent to continent using fibre optics, but the killer application is using this inside chips for interconnect—that is the Holy Grail,” says Zubin Jacob, an electrical engineering professosr leading the research. “What we’ve done is come up with a fundamentally new way of confining light to the nano scale.
At present, the diameter of fibre optic cables is limited to about one thousandth of a millimetre. Cables designed by graduate student Saman Jahani and Jacob are 10 times smaller—small enough to replace copper wiring still used on computer chips. (To put that into perspective, a dime is about one millimetre thick.)


Cancer Detection In Its Earliest Stages

An international team of researchers led by Professor Romain Quidant from The Institute of Photonic Sciences (ICFO ) -Spain -, report on the successful development of a “lab-on-a-chip” platform capable of detecting protein cancer markers in the blood using the very latest advances in plasmonics, nano-fabrication, microfluids and surface chemistry. The device is able to detect very low concentrations of protein cancer markers, enabling diagnoses of the disease in its earliest stages. This cancer-tracking nano-device shows great promise as a tool for future cancer treatments, not only because of its reliability, sensitivity and potential low cost, but also because of its easy carry-on portable properties, which is foreseen to facilitate effective diagnosis and suitable treatment procedures in remote places with difficult access to hospitals or medical clinics.

Although very compact (only a few cm2), the lab-on-a-chip hosts various sensing sites distributed across a network of fluidic micro-channels that enables it to conduct multiple analyses. Gold nano-particles lie on the surface of the chip and are chemically programed with an antibody receptor in such a way that they are capable of specifically attracting the protein markers circulating in blood. When a drop of blood is injected into the chip, it circulates through the micro-channels and if cancer markers are present in the blood, they will stick to the nano-particles located on the micro-channels as they pass by, setting off changes in what is known as the “plasmonic resonance”. The device monitors these changes, the magnitude of which are directly related to the concentration/number of markers in the patient blood thus providing a direct assessment of the risk for the patient to develop a cancer.


How To Build A Nanocomputer Using Graphene

A team of researchers from the University of California, Riverside’s Bourns College of Engineering, led by Alexander Balandin and Roger Lake, have greatly facilitate the use of graphene in electronic devices. A transistor implemented with graphene will be very fast but will suffer from leakage currents and power dissipation while in the off state because of the absence of the energy band gap. Efforts to induce a band-gap in graphene via quantum confinement or surface functionalization have not resulted in a breakthrough. Now, thanks to the University of California Riverside team findings, graphene applications in electronic circuits for information processing are feasible.

Graphene is a single-atom thick carbon crystal with unique properties beneficial for electronics including extremely high electron mobility and phonon thermal conductivity. However, graphene does not have an energy band gap, which is a specific property of semiconductor materials that separate electrons from holes and allows a transistor implemented with a given material to be completely switched off

Most researchers have tried to change graphene to make it more like conventional semiconductors for applications in logic circuits,” Balandin said. “This usually results in degradation of graphene properties. For example, attempts to induce an energy band gap commonly result in decreasing electron mobility while still not leading to sufficiently large band gap.
We decided to take alternative approach,” Balandin said. “Instead of trying to change graphene, we changed the way the information is processed in the circuits.”


Nanowires concentrate15 Times Sun Light Intensity

Scientists from the Nano-Science Center at the Niels Bohr Institut, Denmark and the Ecole Polytechnique Fédérale de Lausanne, Switzerland, have shown that a single nanowire can concentrate the sunlight up to 15 times of the normal sun light intensity. The results are surprising and the potential for developing a new type of highly efficient solar cells is great.

Due to some unique physical light absorption properties of nanowires, the limit of how much energy we can utilize from the sun’s rays is higher than previous believed. These results demonstrate the great potential of development of nanowire-based solar cells, says PhD Peter Krogstrup on the surprising discovery that is described in the journal Nature Photonics.

3-D Nanoscale Printing

Thanks to a novel laser lithography method, Nanoscribe GmbH, a spin-off of Karlsruhe Institute of Technology (KIT) – Germany, presents the world’s fastest 3D printer of micro- and nanostructures. With this printer, smallest three-dimensional objects, often smaller than the diameter of a human hair, can be manufactured with minimum time consumption and maximum resolution.
nanoscale spacecraft
Miniature-spacecraft printed with a Photonic Professional GT system in less than one minute.

Nanoscribe systems are used to print polymer waveguides reaching data transfer rates of more than 5 terabits per second.
Biosciences produce tailored scaffolds for cell growth studies among others. In materials research, functional materials of enhanced performance are developed for lightweight construction to reduce the consumption of resources.


A Northwestern University research team has found a way to manufacture single laser devices that are the size of a virus particle and that operate at room temperature. These plasmonic nanolasers could be readily integrated into silicon-based photonic devices, all-optical circuits and nanoscale biosensors. Reducing the size of photonic and electronic elements is critical for ultra-fast data processing and ultra-dense information storage. The miniaturization of a key, workhorse instrument — the laser — is no exception. The results are published in the journal Nano Letters.

“Coherent light sources at the nanometer scale are important not only for exploring phenomena in small dimensions but also for realizing optical devices with sizes that can beat the diffraction limit of light,” said Teri Odom , a nanotechnology expert who led the research.


How To Diagnose Lung Diseases at Early Stage

Severe lung diseases are among the leading causes of death worldwide. To date they have been difficult to diagnose at an early stage. Within an international collaboration scientists from Munich- Germany – now developed an X-ray technology to do just that. Now they are working on bringing the procedure into medical practice.
X-Ray Nanotechnology.
A combination of dark-field and conventional transmission information allows for a clear distinction of healthy versus emphysematous tissue and an assessment of the regional distribution of the disease. From such images, a doctor might in future not only see if a patient is diseased but also which parts of the lung are affected and how much.
Especially in early stages of the disease, identification, precise quantification and localization of emphysema through the new technology would be very helpful”, says Professor Maximilian Reiser, head of the Institute for Clinical Radiology at Ludwig-Maximilians-University Munich.