Scientists Demonstrate Pathway to Forerunner of Rugged Nanotubes That Could Lead to Widespread Industrial Fabrication


 

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Scientists have identified a chemical pathway to an innovative insulating nanomaterial that could lead to large-scale industrial production for a variety of uses – including in spacesuits and military vehicles. The nanomaterial — thousands of times thinner than a human hair, stronger than steel, and noncombustible — could block radiation to astronauts and help shore up military vehicle armor, for example.

Collaborative researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have proposed a step-by-step chemical pathway to the precursors of this nanomaterial, known as boron nitride nanotubes (BNNT), which could lead to their large-scale production. 

“Pioneering work”

The breakthrough brings together plasma physics and quantum chemistry and is part of the expansion of research at PPPL. “This is pioneering work that takes the Laboratory in new directions,” said PPPL physicist Igor Kaganovich, principal investigator of the BNNT project and co-author of the paper that details the results in the journal Nanotechnology.

Collaborators identified the key chemical pathway steps as the formation of molecular nitrogen and small clusters of boron, which can chemically react together as the temperature created by a plasma jet cools, said lead author Yuri Barsukov of the Peter the Great St. Petersburg Polytechnic University. He developed the chemical reaction pathways by performing quantum chemistry simulations with the assistance of Omesh Dwivedi, a PPPL intern from Drexel University, and Sierra Jubin, a graduate student in the Princeton Program in Plasma Physics.

The interdisciplinary team included Alexander Khrabry, a former PPPL researcher now at Lawrence Livermore National Laboratory who developed a thermodynamic code used in this research, and PPPL physicist Stephane Ethier who helped the students compile the software and set up the simulations. 

The results solved the mystery of how molecular nitrogen, which has the second strongest chemical bond among diatomic, or double-atom molecules, can nonetheless break apart through reactions with boron to form various boron-nitride molecules, Kaganovich said. “We spent considerable amount of time thinking about how to get boron – nitride compounds from a mixture of boron and nitrogen,” he said. “What we found was that small clusters of boron, as opposed to much larger boron droplets, readily interact with nitrogen molecules. That’s why we needed a quantum chemist to go through the detailed quantum chemistry calculations with us.”

BNNTs have properties similar to carbon nanotubes, which are produced by the ton and found in everything from sporting goods and sportswear to dental implants and electrodes. But the greater difficulty of producing BNNTs has limited their applications and availability. 

Chemical pathway

Demonstration of a chemical pathway to the formation of BNNT precursors could facilitate BNNT production. The process of BNNT synthesis begins when scientists use a 10,000-degree plasma jet to turn boron and nitrogen gas into plasma consisting of free electrons and atomic nuclei, or ions, embedded in a background gas. This shows how the process unfolds:

− The jet evaporates the boron while the molecular nitrogen largely stays intact;
− The boron condenses into droplets as the plasma cools;
− The droplets form small clusters as the temperature falls to a few thousand degrees;
− The critical next step is the reaction of nitrogen with small clusters of boron molecules to form boron-nitrogen chains;
− The chains grow longer by colliding with one another and fold into precursors of boron nitride nanotubes.

“During the high-temperature synthesis the density of small boron clusters is low,” Barsukov said. “This is the main impediment to large-scale production.”

The findings have opened a new chapter in BNNT nanomaterial synthesis. “After two years of work we have found the pathway,” Kaganovich said. “As boron condenses it forms big clusters that nitrogen doesn’t react with. But the process starts with small clusters that nitrogen reacts with and there is still a percentage of small clusters as the droplets grow larger,” he said.

“The beauty of this work,” he added, “is that since we had experts in plasma and fluid mechanics and quantum chemistry we could go through all these processes together in an interdisciplinary group. Now we need to compare possible BNNT output from our model with experiments. That will be the next stage of modeling.”

Read the original article on Princeton Plasma Physics Lab.

Rice-Sized Laser Powered One Electron at a Time (Through Quantum Dots): Is This a Foundation for Quantum Computing?


Princeton QD Petta-dqd_300Princeton University researchers have built a rice grain-sized laser powered by single electrons tunneling through artificial atoms known as quantum dots. The tiny microwave laser, or “maser,” is a demonstration of the fundamental interactions between light and moving electrons.

The researchers built the device — which uses about one-billionth the electric current needed to power a hair dryer — while exploring how to use quantum dots, which are bits of semiconductor material that act like single atoms, as components for quantum computers.

“It is basically as small as you can go with these single-electron devices,” said Jason Petta, an associate professor of physics at Princeton who led the study, which was published in the journal Science.

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Princeton University researchers have built a rice grain-sized microwave laser, or “maser,” powered by single electrons that demonstrates the fundamental interactions between light and moving electrons, and is a major step toward building quantum-computing systems out of semiconductor materials. A battery forces electrons to tunnel one by one through two double quantum dots located at each end of a cavity (above), moving from a higher energy level to a lower energy level and in the process giving off microwaves that build into a coherent beam of light. (Photo courtesy of Jason Petta, Department of Physics)

The device demonstrates a major step forward for efforts to build quantum-computing systems out of semiconductor materials, according to co-author and collaborator Jacob Taylor, an adjunct assistant professor at the Joint Quantum Institute, University of Maryland-National Institute of Standards and Technology. “I consider this to be a really important result for our long-term goal, which is entanglement between quantum bits in semiconductor-based devices,” Taylor said.

The original aim of the project was not to build a maser, but to explore how to use double quantum dots — which are two quantum dots joined together — as quantum bits, or qubits, the basic units of information in quantum computers.

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Yinyu Liu, first author of the study and a graduate student in Princeton’s Department of Physics, holds a prototype of the device. (Photo by Catherine Zandonella, Office of the Dean for Research)

“The goal was to get the double quantum dots to communicate with each other,” said Yinyu Liu, a physics graduate student in Petta’s lab. The team also included graduate student Jiri Stehlik and associate research scholar Christopher Eichler in Princeton’s Department of Physics, as well as postdoctoral researcher Michael Gullans of the Joint Quantum Institute.

Because quantum dots can communicate through the entanglement of light particles, or photons, the researchers designed dots that emit photons when single electrons leap from a higher energy level to a lower energy level to cross the double dot.

Each double quantum dot can only transfer one electron at a time, Petta explained. “It is like a line of people crossing a wide stream by leaping onto a rock so small that it can only hold one person,” he said. “They are forced to cross the stream one at a time. These double quantum dots are zero-dimensional as far as the electrons are concerned — they are trapped in all three spatial dimensions.”

Petta rice laser_diagram1

When the power (P) is turned on, single electrons (small arrows) begin to flow through the two double quantum dots (Left DQD and Right DQD) from the drain (D) to the source (S). As the electrons move from the higher energy level to the lower energy level, they give off particles of light in the microwave region of the spectrum. These microwaves bounce off mirrors on either side of the cavity (k-in and k-out) to produce the maser’s beam. (Photo courtesy of Science/AAAS)

The researchers fabricated the double quantum dots from extremely thin nanowires (about 50 nanometers, or a billionth of a meter, in diameter) made of a semiconductor material called indium arsenide. They patterned the indium arsenide wires over other even smaller metal wires that act as gate electrodes, which control the energy levels in the dots.

To construct the maser, they placed the two double dots about 6 millimeters apart in a cavity made of a superconducting material, niobium, which requires a temperature near absolute zero, around minus 459 degrees Fahrenheit. “This is the first time that the team at Princeton has demonstrated that there is a connection between two double quantum dots separated by nearly a centimeter, a substantial distance,” Taylor said.

When the device was switched on, electrons flowed single-file through each double quantum dot, causing them to emit photons in the microwave region of the spectrum. These photons then bounced off mirrors at each end of the cavity to build into a coherent beam of microwave light.

One advantage of the new maser is that the energy levels inside the dots can be fine-tuned to produce light at other frequencies, which cannot be done with other semiconductor lasers in which the frequency is fixed during manufacturing, Petta said. The larger the energy difference between the two levels, the higher the frequency of light emitted.

Petta rice laser_diagram2

A double quantum dot as imaged by a scanning electron microscope. Current flows one electron at a time through two quantum dots (red circles) that are formed in an indium arsenide nanowire. (Photo courtesy of Science/AAAS)

Claire Gmachl, who was not involved in the research and is Princeton’s Eugene Higgins Professor of Electrical Engineering and a pioneer in the field of semiconductor lasers, said that because lasers, masers and other forms of coherent light sources are used in communications, sensing, medicine and many other aspects of modern life, the study is an important one.

“In this paper the researchers dig down deep into the fundamental interaction between light and the moving electron,” Gmachl said. “The double quantum dot allows them full control over the motion of even a single electron, and in return they show how the coherent microwave field is created and amplified. Learning to control these fundamental light-matter interaction processes will help in the future development of light sources.”

The paper, “Semiconductor double quantum dot micromaser,” was published in the journal Science on Jan. 16, 2015. The research was supported by the David and Lucile Packard Foundation, the National Science Foundation (DMR-1409556 and DMR-1420541), the Defense Advanced Research Projects Agency QuEST (HR0011-09-1-0007), and the Army Research Office (W911NF-08-1-0189).

Contact lens merges plastics and active electronics via 3-D printing


Google develop smart contact lens to measure glucose levels in tears - 17 Jan 2014As part of a project demonstrating new 3-D printing techniques, Princeton researchers have embedded tiny light-emitting diodes into a standard contact lens, allowing the device to project beams of colored light.

Michael McAlpine, the lead researcher, cautioned that the lens is not designed for actual use—for one, it requires an external power supply. Instead, he said the team created the device to demonstrate the ability to “3-D print” electronics into complex shapes and materials.

“This shows that we can use 3-D printing to create complex electronics including semiconductors,” said McAlpine, an assistant professor of mechanical and aerospace engineering. “We were able to 3-D print an entire device, in this case an LED.”

The hard is made of plastic. The researchers used tiny crystals, called quantum dots, to create the LEDs that generated the colored light. Different size dots can be used to generate various colors.

“We used the quantum dots [also known as nanoparticles] as an ink,” McAlpine said. “We were able to generate two different colors, orange and green.”

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The contact lens is also part of an ongoing effort to use 3-D printing to assemble diverse, and often hard-to-combine, materials into functioning devices. In the recent past, a team of Princeton professors including McAlpine created a bionic ear out of living cells with an embedded antenna that could receive radio signals.

Yong Lin Kong, a researcher on both projects, said the bionic ear presented a different type of challenge.

McAlpine and Yong Lin Kong, a graduate student in mechanical and aerospace engineering, use a custom-built 3-D printer to create the electronics described in their research. Credit: Frank Wojciechowski

“The main focus of the project was to demonstrate the merger of electronics and biological materials,” said Kong, a graduate student in mechanical and aerospace engineering.

Kong, the lead author of the Oct. 31 article describing the current work in the journal Nano Letters, said that the contact lens project, on the other hand, involved the printing of active electronics using diverse materials. The materials were often mechanically, chemically or thermally incompatible—for example, using heat to shape one material could inadvertently destroy another material in close proximity. The team had to find ways to handle these incompatibilities and also had to develop new methods to print electronics, rather than use the techniques commonly used in the electronics industry.

“For example, it is not trivial to pattern a thin and uniform coating of nanoparticles and polymers without the involvement of conventional microfabrication techniques, yet the thickness and uniformity of the printed films are two of the critical parameters that determine the performance and yield of the printed active device,” Kong said.

To solve these interdisciplinary challenges, the researchers collaborated with Ian Tamargo, who graduated this year with a bachelor’s degree in chemistry; Hyoungsoo Kim, a postdoctoral research associate and fluid dynamics expert in the mechanical and aerospace engineering department; and Barry Rand, an assistant professor of electrical engineering and the Andlinger Center for Energy and the Environment.

McAlpine said that one of 3-D printing’s greatest strengths is its ability to create electronics in complex forms. Unlike traditional electronics manufacturing, which builds circuits in flat assemblies and then stacks them into three dimensions, 3-D printers can create vertical structures as easily as horizontal ones.

“In this case, we had a cube of LEDs,” he said. “Some of the wiring was vertical and some was horizontal.”

To conduct the research, the team built a new type of 3-D printer that McAlpine described as “somewhere between off-the-shelf and really fancy.” Dan Steingart, an assistant professor of mechanical and and the Andlinger Center, helped design and build the new printer, which McAlpine estimated cost in the neighborhood of $20,000.

McAlpine said that he does not envision 3-D printing replacing traditional manufacturing in electronics any time soon; instead, they are complementary technologies with very different strengths. Traditional manufacturing, which uses lithography to create electronic components, is a fast and efficient way to make multiple copies with a very high reliability. Manufacturers are using 3-D printing, which is slow but easy to change and customize, to create molds and patterns for rapid prototyping.

Prime uses for 3-D printing are situations that demand flexibility and that need to be tailored to a specific use. For example, conventional manufacturing techniques are not practical for medical devices that need to be fit to a patient’s particular shape or devices that require the blending of unusual materials in customized ways.

“Trying to print a cellphone is probably not the way to go,” McAlpine said. “It is customization that gives the power to 3-D printing.”

In this case, the researchers were able to custom 3-D print electronics on a contact lens by first scanning the lens, and feeding the geometric information back into the printer. This allowed for conformal 3-D printing of an LED on the contact lens.

Explore further: Princeton team explores 3D-printed quantum dot LEDs

More information: “3D Printed Quantum Dot Light-Emitting Diodes.” Nano Lett., 2014, 14 (12), pp 7017–7023 DOI: 10.1021/nl5033292

Fully 3D-printed quantum dot LEDs


1-3D LED Print id37985_1By Michael Berger – Nanowerk

To date, the 3D printing of electronic components has been limited to the printing of batteries, strain sensors, interdigitated-electrode capacitors and passive metallic structures such as interconnects and antennas on surfaces or within biological organs.

The ability to directly and seamlessly incorporate materials with a range of diverse functionalities with 3D printing is particularly attractive as it could allow the simultaneous, comprehensive, and direct printing of structural, biological, and electronic materials that capture the complete spectra of material properties. The free-form generation of active electronics in unique architectures which transcend the planarity inherent to conventional microfabrication techniques has been an area of increasing scientific interest. Yet, attaining seamless interweaving of electronics is challenging due to the inherent material incompatibilities and geometrical constraints of traditional micro-fabrication processing techniques.

At the fundamental level, 3D printing should be entirely capable of creating spatially heterogeneous multi-material structures by dispensing a wide range of material classes with disparate viscosities and functionalities, including semiconducting colloidal nanomaterials, elastomeric matrices, organic polymers, and liquid and solid metals. “The big push in 3D printing these days is to try to print two or more polymers at once,” Michael McAlpine, an assistant professor of mechanical and aerospace engineering at Princeton University, tells Nanowerk. “In our latest research, we go way beyond that. We show that we can print interwoven structures of quantum dots, polymers, metal nanoparticles, etc, to create the first fully 3D printed LEDs, in which every component is 3D printed.” This demonstration represents a proof of concept in combining active nanoelectronic components with the versatility of 3D printing, which enables the three-dimensional free-form fabrication of active electronics.

3D printed quantum dot light-emitting diode (QLED)

3D printed quantum dot light-emitting diode (QLED) on a 3D scanned curvilinear substrate. This CAD model shows the QD-LED components and conformal integration onto the curvilinear substrate. (Reprinted with permission by American Chemical Society)

McAlpine and his team published their findings in Nano Letters (“3D Printed Quantum Dot Light-Emitting Diodes”). “Using this approach, we can create unique structures, such as 2x2x2 arrays of LEDs, in which the electrical wiring runs horizontal and vertical, to create a multi-color 3D stack of LEDs,” notes Yong Lin Kong, a graduate student in McAlpine’s group who led this project and first author of the paper. “We also use 3D scanning to carefully scan a contact lens and store the specific topology of that lens, and then alter our 3D printing to adjust to that topology, allowing us to conformally 3D print LEDs on a contact lens.

This may have use in electronic contact lens or bionic eye applications in the future.” “This work outlines an exciting breakthrough that enables the direct printing of functional, embedded, active 3D nanoelectronics using only a 3D printer,” he adds. “Indeed, this is the first time to our knowledge that semiconducting nanoparticles have been 3D printed, and the first time that such a broad array of diverse functional materials have been fully interwoven entirely using a 3D printer.” The team’s approach consists of three key steps. First, it identifies electrodes, semiconductors, and polymers that possess desired functionalities and exist in printable formats.

Next, care is taken to ensure that these materials are dissolved in orthogonal solvents so as not to compromise the integrity of underlying layers during the layer-by-layer printing process. Finally, the interwoven patterning of these materials is achieved via direct dispensing in a CAD-designed construct. As a proof of concept of this approach, the researchers demonstrate the 3D printing of quantum dot light-emitting diodes (QLEDs), which involves the design, integration and printing of five classes of materials with distinct material properties. “Specifically, we demonstrate the seamless interweaving of 1) emissive semiconducting inorganic nanoparticles; 2) an elastomeric matrix; 3) organic polymers as charge transport layers; 4) solid and liquid metal leads; and 5) a UV-adhesive transparent substrate layer,” explains Kong. “The printed QLEDs exhibit excellent performance characteristics. The combination of 3D scanning and 3D printing allows for the direct printing of active functional electronics onto the precise topology of a non-flat object.”

3D printed quantum dot light-emitting diode (QLED)

3D printed 2×2×2 multidimensional array of embedded QD-LEDs. (A) Layout of the multi-color 3D QD-LED array design. (Image: McAlpine Group)

He points out that, most excitingly, this approach allows for the free-form fabrication of multi-dimensional nanoelectronics within a complex, interwoven architecture such as a 3D array of embedded QLEDs. The QLEDs printed by McAlpine’s team capture the unique properties of quantum dots: tunable and pure color emission. Further, combining a complementary 3D light-scanning technique with this approach allows for the fabrication of electronics topographically tailored to curvilinear surfaces. “We anticipate that this general strategy can be expanded to 3D print other classes of active devices, such as MEMS devices, transistors, solar cells, and photodiodes,” says McAlpine. “Our results suggest a number of exciting applications, including the generation of geometrically tailored devices containing LEDs and multimodal sensors to provide a new tool for optogenetics for studying neural circuitry.”

Co-printing of active electronics with biological constructs could also lead to new bionic devices, such as prosthetic implants that optically stimulate nerve cells. According to the team, future work will address a number of key challenges. These include: 1) increasing the resolution of the 3D printer such that smaller devices can be printed; 2) improving the performance and yield of the printed devices; and 3) incorporating other classes of nanoscale functional building blocks and devices, including semiconductor, plasmonic, and ferroelectric.

Nanotechnology leads to better, cheaper LEDs for phones and lighting


130807133432Princeton, NJ | Posted on September 24th, 2014

Using a new nanoscale structure, the researchers, led by electrical engineering professor Stephen Chou, increased the brightness and efficiency of LEDs made of organic materials (flexible carbon-based sheets) by 57 percent. The researchers also report their method should yield similar improvements in LEDs made in inorganic (silicon-based) materials used most commonly today.

The method also improves the picture clarity of LED displays by 400 percent, compared with conventional approaches. In an article published online August 19 in the journal Advanced Functional Materials, the researchers describe how they accomplished this by inventing a technique that manipulates light on a scale smaller than a single wavelength.

“New nanotechnology can change the rules of the ways we manipulate light,” said Chou, who has been working in the field for 30 years. “We can use this to make devices with unprecedented performance.”

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A LED, or light emitting diode, is an electronic device that emits light when electrical current moves through two terminals. LEDs offer several advantages over incandescent or fluorescent lights: they are far more efficient, compact and have a longer lifetime, all of which are important in portable displays.

Current LEDs have design challenges; foremost among them is to reduce the amount of light that gets trapped inside the LED’s structure. Although they are known for their efficiency, only a very small amount of light generated inside an LED actually escapes.

“It is exactly the same reason that lighting installed inside a swimming pool seems dim from outside – because the water traps the light,” said Chou, the Joseph C. Elgin Professor of Engineering. “The solid structure of a LED traps far more light than the pool’s water.”

In fact, a rudimentary LED emits only about 2 to 4 percent of the light it generates. The trapped light not only makes the LEDs dim and energy inefficient, it also makes them short-lived because the trapped light heats the LED, which greatly reduces its lifespan.

“A holy grail in today’s LED manufacturing is light extraction,” Chou said.

Engineers have been working on this problem. By adding metal reflectors, lenses or other structures, they can increase the light extraction of LEDs. For conventional high-end, organic LEDs, these techniques can increase light extraction to about 38 percent. But these light-extraction techniques cause the display to reflect ambient light, which reduces contrast and makes the image seem hazy.

To combat the reflection of ambient light, engineers now add light-absorbing materials to the display. But Chou said such materials also absorb the light from the LED, reducing its brightness and efficiency by as much as half.

The solution presented by Chou’s team is the invention of a nanotechnology structure called PlaCSH (plasmonic cavity with subwavelength hole-array). The researchers reported that PlaCSH increased the efficiency of light extraction to 60 percent, which is 57 percent higher than conventional high-end organic LEDs. At the same time, the researchers reported that PlaCSH increased the contrast (clarity in ambient light) by 400 percent. The higher brightness also relieves the heating problem caused by the light trapped in standard LEDs.

Chou said that PlaCSH is able to achieve these results because its nanometer-scale, metallic structures are able to manipulate light in a way that bulk material or non-metallic nanostructures cannot.

Chou first used the PlaCSH structure on solar cells, which convert light to electricity. In a 2012 paper, he described how the application of PlaCSH resulted in the absorption of as much as 96 percent of the light striking solar cells’ surface and increased the cells’ efficiency by 175 percent. Chou realized that a device that was good at absorbing light from the outside could also be good at radiating light generated inside the device – offering an efficient solution for both light extraction and the reduction of light reflection.

“From a view point of physics, a good light absorber, which we had for the solar cells, should also be a good light radiator,” he said. “We wanted to experimentally demonstrate this is true in visible light range, and then use it to solve the key challenges in LEDs and displays.”

The physics behind PlaCSH are complex, but the structure is relatively simple. PlaCSH has a layer of light-emitting material about 100 nanometers thick that is placed inside a cavity with one surface made of a thin metal film. The other cavity surface is made of a metal mesh with incredibly small dimensions: it is 15 nanometers thick; and each wire is about 20 nanometers in width and 200 nanometers apart from center to center. (A nanometer is one hundred-thousandth the width of a human hair.)

Because PlaCSH works by guiding the light out of the LED, it is able to focus more of the light toward the viewer. The system also replaces the conventional brittle transparent electrode, making it far more flexible than most current displays.

“It is so flexible and ductile that it can be weaved into a cloth,” Chou said.

Another benefit for manufacturers is cost. The PlaCSH organic LEDs were made by nanoimprint, a technology Chou invented in 1995, which creates nanostructures in a fashion similar to a printing press producing newspapers.

“It is cheap and extremely simple,” Chou said.

Princeton has filed patent applications for both organic and inorganic LEDs using PlaCSH. Chou and his team are now conducting experiments to demonstrate PLaCSH in red and blue organic LEDs, in addition the green LEDs used in the current experiments. They also are demonstrating the system in inorganic LEDs.

Besides Chou, the paper’s authors are Wei Ding, Yuxuan Wang and Hao Chen, graduate students in electrical engineering at Princeton. Support for the research was provided in part by the Defense Advanced Research Projects Agency and the Office of Naval Research. Chou recently was awarded a major grant from the U.S. Department of Energy to further advance the use of PlaCSH as a solution for energy-efficient lighting.

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Nanotechnology triples solar efficiency


By | December 11, 2012, 7:49 PM PST

Nanotechnology traps light for significantly greater solar efficiency.

Nanotechnology traps light for significantly greater solar efficiency.

Princeton University recently announced a new nanotechnology that has demonstrated the ability to triple the efficiency of solar cells by eliminating two of the primary reasons why light is reflected or lost. This breakthrough was achieved by applying a “nano-mesh” to plastics, which would make way for inexpensive, flexible devices, or even greatly improve the efficiency of standard photovoltaic panels, the researchers say.

The nano-mesh is designed to dampen reflection and trap light to be converted into electrical energy (existing technologies cannot fully capture light that enters the cell). Only 4 percent of light is reflected, and as much as 96 percent is absorbed, a press release noted. Its overall efficiency in converting light to energy is 52 percent higher than conventional cells in direct sunlight and up to 175 percent greater on cloudy days with less sun.

For reference, North Carolina’s Semprius Inc., a Siemens backed venture, revealed a prototype of what it called the world’s best solar efficiency at 33.9 percent earlier this year. Princeton didn’t reveal its overal efficiency.

Princeton’s findings were first reported in the November 2nd edition of the journal Optics Express, and exceeded the scientists’ expectations, according to project lead Dr. Stephen Chou. The research was funded by the Defense Advanced Research Projects Agency, the Office of Naval Research and the National Science Foundation. Chou said that the technology would become even more efficient with more experimentation.

Outside of the lab, U.S. PV maker ecoSolargy has already used nanotechnology to boost solar efficiency by an estimated 35 percent over a 20-year period by filling tiny holes that can accumulate dirt, dust, or water. Other approaches that are being taken to improve solar efficiency have been inspired by nature.

A team of researchers at the University of Wisconsin-Madison recently created a design that emulates how sunflowers move to maximize light exposure through an adaptation called heliotropism. One could imagine that any combination of these technologies would constitute another leap forward for solar power.

(Illustration by Dimitri Karetnikov/Chou Lab)QDOTS imagesCAKXSY1K 8