Category Archives: Applications

Scientists from the Semenov Institute of Chemical Physics of the Russian Academy of Sciences (ICP RAS) and the Moscow Institute of Physics and Technology (MIPT) have demonstrated that sensors based on binary metal oxide nanocomposites are sensitive enough to identify terrorist threats and detect environmental pollutants. The results of their study have been published in Sensors and Actuators B: Chemical.

This is a schematic representation of a binary sensor based on two metal oxides, with the nanoparticles of the catalytically active component (1) in yellow and the nanoparticles of the electron donor component (2) represented by the unshaded circles. Credit: the MIPT press office

This is a schematic representation of a binary sensor based on two metal oxides, with the nanoparticles of the catalytically active component (1) in yellow and the nanoparticles of the electron donor component (2) represented by the unshaded circles. Credit: the MIPT press office

Due to rapid industrial growth and the degradation of the environment, there is a growing need for the development of highly effective and selective sensors for pollutant detection. In addition, gas sensors could also be used to monitor potential terrorist threats.

“Choosing the right sensor composition can make a device at least ten times more effective and enable an exceptionally fast response, which is crucial for preventing terrorist attacks,” says Prof. Leonid Trakhtenberg of the Department of Molecular and Chemical Physics at MIPT, who is the leader of the research team and the head of the Laboratory of Functional Nanocomposites at ICP RAS.

According to the research findings, the most promising detection systems are binary metal oxide sensors, in which one component provides a high density of conductive electrons and another is a strong catalyst.

A mixed system of that kind has the two necessary components for effective gas detection, viz., an electron donor and a substance “accommodating” the reaction. An additional factor contributing to faster sensor response is the formation of chemisorption centers, i.e., the chemically active spots on the nanocrystals that facilitate gas molecule adsorption.

“We are planning further research into the possibilities for sensor design presented by the multicomponent metal oxide nanocomposites incorporating nanofibers. The development of new effective sensor compositions will be based on a reasonably balanced approach involving both the experimental tests and the advancement of our theoretical understanding of the sensing mechanisms,” comments Prof. Trakhtenberg.

A rather promising approach to the development of new gas detection systems is the use of “core-shell type” composite metal oxide nanofibers, where the “core” and the “shell” are composed of two different oxides.

At the Annual Conference on Magnetism and Magnetic Materials, imec, a research and innovation center in nano-electronics and digital technologies, presented breakthrough results supporting the building of technology-relevant majority gates based on spin waves. Reporting two industry-first achievements that are crucial for ultralow-power beyond-CMOS technology, imec demonstrated the generation and detection of spin waves in sub-micron-sized magnetic waveguides with wavelengths smaller than 350nm traveling over 10 micrometer in a 500nm wide waveguide, and proposed models for majority operation in nanoscale spin-wave structures.

Spintronic majority gate devices are promising alternatives to CMOS technology for certain applications, for example for arithmetic circuits. Majority gates are devices where the state of the output is determined by the majority of the inputs: if for example more than 50 percent of the inputs are true, the output has to return true. The output of the spin-wave majority gate is then based on the interference of multiple spin waves that propagate in a so-called spin-wave bus, or waveguide. When miniaturized down to the nanoscale, spin-wave majority gates could enable arithmetic circuits that are much more compact and energy-efficient than CMOS-based circuits.

Imec, in collaboration with the University of Kaiserslautern and Paris-Sud University, studied spin-wave propagation in a 10nm thick magnetic waveguide. Importantly, they found that spin waves, excited by an RF-driven antenna, can travel more than 10 micrometers in a 500nm wide waveguide. In a second experiment, they developed an all-electrical detection method for characterizing propagating spin waves in a magnetic bus. Spin waves with wavelengths as miniscule as 340nm could be detected—more than two times smaller than previously achieved industry results—paving the way towards scaled spin-wave conduits.

Through micromagnetic simulations, the operation of a nanoscaled fork-like spin-wave majority structure was successfully demonstrated. At these small dimensions, magneto-electric cells are used instead of antennas to excite and detect the spin waves. The proposed detection scheme allowed imec to capture the majority phase result of the spin-wave interference in a very short time frame, which was less than three nanoseconds.

“Spin-wave majority gates with micro-sized dimensions have previously been reported, however, for them to be CMOS-competitive, they must be scaled and handle waves with nanometer-sized wavelengths,” stated Iuliana Radu, distinguished member of technical staff coordinating Beyond CMOS at imec. “We propose here a method to scale these spin-wave devices into nanometer dimensions. Today’s exceptional results will open routes towards building spin-wave majority gates that promise to outperform CMOS-based logic technology in terms of power and area reduction.”

A tiny machine


October 31, 2016

In 1959 renowned physicist Richard Feynman, in his talk “Plenty of Room at the Bottom,” spoke of a future in which tiny machines could perform huge feats. Like many forward-looking concepts, his molecule and atom-sized world remained for years in the realm of science fiction.

And then, scientists and other creative thinkers began to realize Feynman’s nanotechnological visions.

In the spirit of Feynman’s insight, and in response to the challenges he issued as a way to inspire scientific and engineering creativity, electrical and computer engineers at UC Santa Barbara have developed a design for a functional nanoscale computing device. The concept involves a dense, three-dimensional circuit operating on an unconventional type of logic that could, theoretically, be packed into a block no bigger than 50 nanometers on any side.

“Novel computing paradigms are needed to keep up with the demand for faster, smaller and more energy-efficient devices,” said Gina Adam, postdoctoral researcher at UCSB’s Department of Computer Science and lead author of the paper “Optimized stateful material implication logic for three dimensional data manipulation,” published in the journal Nano Research. “In a regular computer, data processing and memory storage are separated, which slows down computation. Processing data directly inside a three-dimensional memory structure would allow more data to be stored and processed much faster.”

While efforts to shrink computing devices have been ongoing for decades — in fact, Feynman’s challenges as he presented them in his 1959 talk have been met — scientists and engineers continue to carve out room at the bottom for even more advanced nanotechnology. A nanoscale 8-bit adder operating in 50-by-50-by-50 nanometer dimension, put forth as part of the current Feynman Grand Prize challenge by the Foresight Institute, has not yet been achieved. However, the continuing development and fabrication of progressively smaller components is bringing this virus-sized computing device closer to reality, said Dmitri Strukov, a UCSB professor of computer science.

“Our contribution is that we improved the specific features of that logic and designed it so it could be built in three dimensions,” he said.

Key to this development is the use of a logic system called material implication logic combined with memristors — circuit elements whose resistance depends on the most recent charges and the directions of those currents that have flowed through them. Unlike the conventional computing logic and circuitry found in our present computers and other devices, in this form of computing, logic operation and information storage happen simultaneously and locally. This greatly reduces the need for components and space typically used to perform logic operations and to move data back and forth between operation and memory storage. The result of the computation is immediately stored in a memory element, which prevents data loss in the event of power outages — a critical function in autonomous systems such as robotics.

In addition, the researchers reconfigured the traditionally two-dimensional architecture of the memristor into a three-dimensional block, which could then be stacked and packed into the space required to meet the Feynman Grand Prize Challenge.

“Previous groups show that individual blocks can be scaled to very small dimensions, let’s say 10-by-10 nanometers,” said Strukov, who worked at technology company Hewlett-Packard’s labs when they ramped up development of memristors and material implication logic. By applying those results to his group’s developments, he said, the challenge could easily be met.

The tiny memristors are being heavily researched in academia and in industry for their promising uses in memory storage and neuromorphic computing. While implementations of material implication logic are rather exotic and not yet mainstream, uses for it could pop up any time, particularly in energy scarce systems such as robotics and medical implants.

“Since this technology is still new, more research is needed to increase its reliability and lifetime and to demonstrate large scale three-dimensional circuits tightly packed in tens or hundreds of layers,” Adam said.

Robert Wolkow is no stranger to mastering the ultra-small and the ultra-fast. A pioneer in atomic-scale science with a Guinness World Record to boot (for a needle with a single atom at the point), Wolkow’s team, together with collaborators at the Max Plank Institute in Hamburg, have just released findings that detail how to create atomic switches for electricity, many times smaller than what is currently used.

Robert Wolkow, University of Alberta physics professor and the Principal Research Officer at Canada's National Institute for Nanotechnology, has developed a technique to switch a single-atom channel. Credit: John Ulan

Robert Wolkow, University of Alberta physics professor and the Principal Research Officer at Canada’s National Institute for Nanotechnology, has developed a technique to switch a single-atom channel. Credit: John Ulan

What does it all mean? With applications for practical systems like silicon semi-conductor electronics, it means smaller, more efficient, more energy-conserving computers, as just one example of the technology revolution that is unfolding right before our very eyes (if you can squint that hard).

“This is the first time anyone’s seen a switching of a single-atom channel,” explains Wolkow, a physics professor at the University of Alberta and the Principal Research Officer at Canada’s National Institute for Nanotechnology. “You’ve heard of a transistor–a switch for electricity–well, our switches are almost a hundred times smaller than the smallest on the market today.”

Today’s tiniest transistors operate at the 14 nanometer level, which still represents thousands of atoms. Wolkow’s and his team at the University of Alberta, NINT, and his spinoff QSi, have worked the technology down to just a few atoms. Since computers are simply a composition of many on/off switches, the findings point the way not only to ultra-efficient general purpose computing but also to a new path to quantum computing.

“We’re using this technology to make ultra-green, energy-conserving general purpose computers but also to further the development of quantum computers. We are building the most energy conserving electronics ever, consuming about a thousand times less power than today’s electronics.”

While the new tech is small, the potential societal, economic, and environmental impact of Wolkow’s discovery is very large. Today, our electronics consume several percent of the world’s electricity. As the size of the energy footprint of the digital economy increases, material and energy conservation is becoming increasingly important.

Wolkow says there are surprising benefits to being smaller, both for normal computers, and, for quantum computers too. “Quantum systems are characterized by their delicate hold on information. They’re ever so easily perturbed. Interestingly though, the smaller the system gets, the fewer upsets.” Therefore, Wolkow explains, you can create a system that is simultaneously amazingly small, using less material and churning through less energy, while holding onto information just right.

When the new technology is fully developed, it will lead to not only a smaller energy footprint but also more affordable systems for consumers. “It’s kind of amazing when everything comes together,” says Wolkow.

Wolkow is one of the few people in the world talking about atom-scale manufacturing and believes we are witnessing the beginning of the revolution to come. He and his team have been working with large-scale industry leader Lockheed Martin as the entry point to the market.

“It’s something you don’t even hear about yet, but atom-scale manufacturing is going to be world-changing. People think it’s not quite doable but, but we’re already making things out of atoms routinely. We aren’t doing it just because. We are doing it because the things we can make have ever more desirable properties. They’re not just smaller. They’re different and better. This is just the beginning of what will be at least a century of developments in atom-scale manufacturing, and it will be transformational.”

“Time Resolved Single Dopant Charge Dynamics in Silicon” appeared in the October 26 edition of Nature Communications, an open-access journal in the group of Nature, world-leading scientific publications.

Researchers have developed a prototype of a next-generation lithium-sulphur battery which takes its inspiration in part from the cells lining the human intestine. The batteries, if commercially developed, would have five times the energy density of the lithium-ion batteries used in smartphones and other electronics.

This is a computer visualization of villi-like battery material. Credit: Teng Zhao

This is a computer visualization of villi-like battery material. Credit: Teng Zhao

The new design, by researchers from the University of Cambridge, overcomes one of the key technical problems hindering the commercial development of lithium-sulphur batteries, by preventing the degradation of the battery caused by the loss of material within it. The results are reported in the journal Advanced Functional Materials.

Working with collaborators at the Beijing Institute of Technology, the Cambridge researchers based in Dr Vasant Kumar’s team in the Department of Materials Science and Metallurgy developed and tested a lightweight nanostructured material which resembles villi, the finger-like protrusions which line the small intestine. In the human body, villi are used to absorb the products of digestion and increase the surface area over which this process can take place.

In the new lithium-sulphur battery, a layer of material with a villi-like structure, made from tiny zinc oxide wires, is placed on the surface of one of the battery’s electrodes. This can trap fragments of the active material when they break off, keeping them electrochemically accessible and allowing the material to be reused.

“It’s a tiny thing, this layer, but it’s important,” said study co-author Dr Paul Coxon from Cambridge’s Department of Materials Science and Metallurgy. “This gets us a long way through the bottleneck which is preventing the development of better batteries.”

A typical lithium-ion battery is made of three separate components: an anode (negative electrode), a cathode (positive electrode) and an electrolyte in the middle. The most common materials for the anode and cathode are graphite and lithium cobalt oxide respectively, which both have layered structures. Positively-charged lithium ions move back and forth from the cathode, through the electrolyte and into the anode.

The crystal structure of the electrode materials determines how much energy can be squeezed into the battery. For example, due to the atomic structure of carbon, each carbon atom can take on six lithium ions, limiting the maximum capacity of the battery.

Sulphur and lithium react differently, via a multi-electron transfer mechanism meaning that elemental sulphur can offer a much higher theoretical capacity, resulting in a lithium-sulphur battery with much higher energy density. However, when the battery discharges, the lithium and sulphur interact and the ring-like sulphur molecules transform into chain-like structures, known as a poly-sulphides. As the battery undergoes several charge-discharge cycles, bits of the poly-sulphide can go into the electrolyte, so that over time the battery gradually loses active material.

The Cambridge researchers have created a functional layer which lies on top of the cathode and fixes the active material to a conductive framework so the active material can be reused. The layer is made up of tiny, one-dimensional zinc oxide nanowires grown on a scaffold. The concept was trialled using commercially-available nickel foam for support. After successful results, the foam was replaced by a lightweight carbon fibre mat to reduce the battery’s overall weight.

“Changing from stiff nickel foam to flexible carbon fibre mat makes the layer mimic the way small intestine works even further,” said study co-author Dr Yingjun Liu.

This functional layer, like the intestinal villi it resembles, has a very high surface area. The material has a very strong chemical bond with the poly-sulphides, allowing the active material to be used for longer, greatly increasing the lifespan of the battery.

“This is the first time a chemically functional layer with a well-organised nano-architecture has been proposed to trap and reuse the dissolved active materials during battery charging and discharging,” said the study’s lead author Teng Zhao, a PhD student from the Department of Materials Science & Metallurgy. “By taking our inspiration from the natural world, we were able to come up with a solution that we hope will accelerate the development of next-generation batteries.”

For the time being, the device is a proof of principle, so commercially-available lithium-sulphur batteries are still some years away. Additionally, while the number of times the battery can be charged and discharged has been improved, it is still not able to go through as many charge cycles as a lithium-ion battery. However, since a lithium-sulphur battery does not need to be charged as often as a lithium-ion battery, it may be the case that the increase in energy density cancels out the lower total number of charge-discharge cycles.

“This is a way of getting around one of those awkward little problems that affects all of us,” said Coxon. “We’re all tied in to our electronic devices – ultimately, we’re just trying to make those devices work better, hopefully making our lives a little bit nicer.”

Harvard University researchers have made the first entirely 3D-printed organ-on-a-chip with integrated sensing. Built by a fully automated, digital manufacturing procedure, the 3D-printed heart-on-a-chip can be quickly fabricated in customized form factors allowing researchers to easily collect reliable data for short-term and long-term studies.

This new approach to manufacturing may one day allow researchers to rapidly design organs-on-chips, also known as microphysiological systems, that match the properties of a specific disease or even an individual patient’s cells.

The research is published in Nature Materials.

“This new programmable approach to building organs-on-chips not only allows us to easily change and customize the design of the system by integrating sensing but also drastically simplifies data acquisition,” said Johan Ulrik Lind, first author of the paper and postdoctoral fellow at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS). Lind is also a researcher at the Wyss Institute for Biologically Inspired Engineering at Harvard University.

“Our microfabrication approach opens new avenues for in vitro tissue engineering, toxicology and drug screening research,” said Kit Parker, Tarr Family Professor of Bioengineering and Applied Physics at SEAS, who coauthored the study. Parker is also a Core Faculty Member of the Wyss Institute.

Organs-on-chips mimic the structure and function of native tissue and have emerged as a promising alternative to traditional animal testing. Harvard researchers have developed microphysiological systems that mimic the microarchitecture and functions of lungs, hearts, tongues and intestines.

However, the fabrication and data collection process for organs-on-chips is expensive and laborious. Currently, these devices are built in clean rooms using a complex, multi-step lithographic process and collecting data requires microscopy or high-speed cameras.

“Our approach was to address these two challenges simultaneously via digital manufacturing,” said Travis Busbee, coauthor of the paper and graduate student in the Lewis Lab. “By developing new printable inks for multi-material 3D printing, we were able to automate the fabrication process while increasing the complexity of the devices.”

The researchers developed six different inks that integrated soft strain sensors within the micro-architecture of the tissue. In a single, continuous procedure, the team 3D printed those materials into a cardiac microphysiological device — a heart on a chip — with integrated sensors.

“We are pushing the boundaries of three-dimensional printing by developing and integrating multiple functional materials within printed devices,” said Jennifer Lewis, Hansjorg Wyss Professor of Biologically Inspired Engineering, and coauthor of the study. “This study is a powerful demonstration of how our platform can be used to create fully functional, instrumented chips for drug screening and disease modeling.”

Lewis is also a Core Faculty Member of the Wyss Institute.

The chip contains multiple wells, each with separate tissues and integrated sensors, allowing researchers to study many engineered cardiac tissues at once. To demonstrate the efficacy of the device, the team performed drug studies and longer-term studies of gradual changes in the contractile stress of engineered cardiac tissues, which can occur over the course of several weeks.

“Researchers are often left working in the dark when it comes to gradual changes that occur during cardiac tissue development and maturation because there has been a lack of easy, non-invasive ways to measure the tissue functional performance,” said Lind. “These integrated sensors allow researchers to continuously collect data while tissues mature and improve their contractility. Similarly, they will enable studies of gradual effects of chronic exposure to toxins.”

“Translating microphysiological devices into truly valuable platforms for studying human health and disease requires that we address both data acquisition and manufacturing of our devices,” said Parker. “This work offers new potential solutions to both of these central challenges.”

SEMI and Messe München today announced that SEMICON Europa will co-locate with productronica and electronica (alternating years) in Munich, Germany. For the first time, the co-located events (productronica and SEMICON Europa) will be held next year (14-17 November 2017), creating the strongest single event for electronics manufacturing in Europe, and broadening the range of attendees across the electronics supply chain.

productronica, the world’s leading trade fair for electronics development and production, and electronica, the world’s leading trade fair for electronic components, systems and applications, will now offer attendees an extended platform. With the inclusion of SEMICON Europa, which is focused on the electronics manufacturing supply chain and largely the semiconductor manufacturing, the co-located events will expand attendee opportunities to exchange ideas and promote technological progress.

Falk Senger, managing director of Messe München, says: “The co-location of these events strengthens the global orientation of electronica and productronica, in addition to reinforcing the importance of Munich as one of the epicenters of the international electronics industry.”

SEMICON Europa features the most advanced and innovative electronics manufacturing platform in Europe. Key segments include: semiconductor front-end and back-end manufacturing, MEMS/sensors, secondary equipment, advanced packaging, and applications such as the Internet of Things (IoT).

“The co-location of SEMICON Europa with productronica and electronica is an excellent fit with SEMI’s global trade association strategy to connect the breadth of the global electronics manufacturing supply chain. SEMICON Europa brings a wide range of focused programs that address Europe’s electronics manufacturing issues and opportunities,” says Denny McGuirk, president and CEO of SEMI.

Munich is a convenient central location in Europe with easy access for international visitors. The co-located events will brings tens of thousands of visitors together to connect for electronics business.

To learn more about SEMI (and SEMICON Europa) and Messe München  (and electronica and productronica), please visit the websites.

Knowles, Goertek and AAC ranked as the top three global suppliers of packaged MEMS microphones for 2015, according to the latest analysis from IHS Markit (NASDAQ: INFO), a world leader in critical information, analytics and solutions.

MEMS (micro-electromechanical systems) technology is utilized to produce microphones used in laptops, hearing aids, wearables and smartphones among many other products. Last year, MEMS microphones remained the healthiest sensors segment for suppliers, in terms of unit volume and revenue, said Marwan Boustany, senior analyst for IHS Technology.

“Our updated analysis of 2015 MEMS microphone supplier market share, shows that Knowles remained the dominant supplier with more than two times the units and revenue of the second-place supplier, Goertek,” Boustany said. “In addition to offering a wide range of analog and digital output microphones for many applications, Knowles has also started shipping its VoiceIQ ‘intelligent’ microphones with local processing as it seeks to address both mobile and IOT applications.”

2016 mems mic growth

Strong growth for MEMS’ runner-ups

Goertek MEMS microphone units grew by an impressive 104 percent CAGR between 2011 and 2015, thanks in large part to its design wins in Apple, the IHS Markit analysis shows. Apple accounts for approximately 70 percent (in units) of Goertek’s MEMS microphone business in 2015. Goertek entered in large volume in the iPhone in 2014 and has since continued to increase its share; this has had the impact of reducing the share of AAC and Knowles in subsequent years.

While still solidly in third position among packaged MEMS suppliers after Goertek, AAC has faced challenges from Goertek in both Apple and in Chinese OEMs. This has resulted in a reduction in unit volume shipped by AAC in 2015 of almost 9 percent, IHS Markit says. However, AAC invested in a new technology for MEMS microphones in 2016 when it officially partnered with Vesper MEMS, a piezoelectric MEMS microphone start-up.

Boosting audio performance in handsets

The general adoption trend for microphones in smartphones has been towards higher performance, IHS Markit says. Driving this trend: OEMs want better quality audio for calls and hand-free communication, noise cancellation, voice recognition such as Siri and Google Now, as well as the availability of lower-cost microphones due to the erosion of ASP (average selling price).

“These types of use cases also drive high-performance microphone adoption in smart watches, tablets, noise cancelling earphones, hearing aids and increasingly in automotive cabins,” Boustany said.

Beyond performance, the average number of microphones per handset increased in 2015 due to Apple adopting four microphones in its iPhone 6S, with most other OEMs using two or three microphones in their mid- to high-end smartphones, the IHS Markit analysis shows. In tablets, smart watches and hearing aids, the number of microphones is between one and two. Adoption of microphones in automotive cabins can potentially exceed eight, depending on use cases and implementation choices in the future.

Knowles tops list for die makers, too

According to the IHS Technology analysis, Knowles – which produces its own microphone dies – holds the number one spot for market share in MEMS microphone production, with a dominant 43 percent market share.

Infineon acts as the major supplier of MEMS microphone dies to Goertek, AAC and BSE among others and stands solidly in second place with a 31 percent market share. In third place is Omron, which has supplied into STMicroelectronics, ACC and Goertek among others and has a 13 percent market share, the analysis shows. Neither Infineon nor Omron supply fully packaged MEMS microphone die.

A new design for solar cells that uses inexpensive, commonly available materials could rival and even outperform conventional cells made of silicon.

A tandem perovskite solar cell boosts efficiency by absorbing high- and low-energy photons from the sun. Credit: Rongrong Cheacharoen/Stanford University

A tandem perovskite solar cell boosts efficiency by absorbing high- and low-energy photons from the sun. Credit: Rongrong Cheacharoen/Stanford University

Writing in the Oct. 21 edition of Science, researchers from Stanford and Oxford describe using tin and other abundant elements to create novel forms of perovskite – a photovoltaic crystalline material that’s thinner, more flexible and easier to manufacture than silicon crystals.

“Perovskite semiconductors have shown great promise for making high-efficiency solar cells at low cost,” said study co-author Michael McGehee, a professor of materials science and engineering at Stanford. “We have designed a robust, all-perovskite device that converts sunlight into electricity with an efficiency of 20.3 percent, a rate comparable to silicon solar cells on the market today.”

The new device consists of two perovskite solar cells stacked in tandem. Each cell is printed on glass, but the same technology could be used to print the cells on plastic, McGehee added.

“The all-perovskite tandem cells we have demonstrated clearly outline a roadmap for thin-film solar cells to deliver over 30 percent efficiency,” said co-author Henry Snaith, a professor of physics at Oxford. “This is just the beginning.”

Tandem technology

Previous studies showed that adding a layer of perovskite can improve the efficiency of silicon solar cells. But a tandem device consisting of two all-perovskite cells would be cheaper and less energy-intensive to build, the authors said.

“A silicon solar panel begins by converting silica rock into silicon crystals through a process that involves temperatures above 3,000 degrees Fahrenheit (1,600 degrees Celsius),” said co-lead author Tomas Leijtens, a postdoctoral scholar at Stanford. “Perovskite cells can be processed in a laboratory from common materials like lead, tin and bromine, then printed on glass at room temperature.”

But building an all-perovskite tandem device has been a difficult challenge. The main problem is creating stable perovskite materials capable of capturing enough energy from the sun to produce a decent voltage.

A typical perovskite cell harvests photons from the visible part of the solar spectrum. Higher-energy photons can cause electrons in the perovskite crystal to jump across an “energy gap” and create an electric current.

A solar cell with a small energy gap can absorb most photons but produces a very low voltage. A cell with a larger energy gap generates a higher voltage, but lower-energy photons pass right through it.

An efficient tandem device would consist of two ideally matched cells, said co-lead author Giles Eperon, an Oxford postdoctoral scholar currently at the University of Washington.

“The cell with the larger energy gap would absorb higher-energy photons and generate an additional voltage,” Eperon said. “The cell with the smaller energy gap can harvest photons that aren’t collected by the first cell and still produce a voltage.”

The smaller gap has proven to be the bigger challenge for scientists. Working together, Eperon and Leijtens used a unique combination of tin, lead, cesium, iodine and organic materials to create an efficient cell with a small energy gap.

“We developed a novel perovskite that absorbs lower-energy infrared light and delivers a 14.8 percent conversion efficiency,” Eperon said. “We then combined it with a perovskite cell composed of similar materials but with a larger energy gap.”

The result: A tandem device consisting of two perovskite cells with a combined efficiency of 20.3 percent.

“There are thousands of possible compounds for perovskites,” Leijtens added, “but this one works very well, quite a bit better than anything before it.”

Seeking stability

One concern with perovskites is stability. Rooftop solar panels made of silicon typically last 25 years or more. But some perovskites degrade quickly when exposed to moisture or light. In previous experiments, perovskites made with tin were found to be particularly unstable.

To assess stability, the research team subjected both experimental cells to temperatures of 212 degrees Fahrenheit (100 degrees Celsius) for four days.

“Crucially, we found that our cells exhibit excellent thermal and atmospheric stability, unprecedented for tin-based perovskites,” the authors wrote.

“The efficiency of our tandem device is already far in excess of the best tandem solar cells made with other low-cost semiconductors, such as organic small molecules and microcrystalline silicon,” McGehee said. “Those who see the potential realize that these results are amazing.”

The next step is to optimize the composition of the materials to absorb more light and generate an even higher current, Snaith said.

“The versatility of perovskites, the low cost of materials and manufacturing, now coupled with the potential to achieve very high efficiencies, will be transformative to the photovoltaic industry once manufacturability and acceptable stability are also proven,” he said.

STMicroelectronics (NYSE: STM) today announced that its LSM6DSM 6-axis Inertial Measurement Unit (IMU) has earned certification for use in next-generation mobile devices running Google Daydream, a high-performance virtual-reality platform, and Tango, a platform that maps 3D space and enables it to be overlaid with virtual objects.

Announced at the Google I/O Developer Conference 2016, Daydream is being built into the newest generation of smartphones and other mobile devices and will operate along with a controller and a viewer to provide an amazing immersive virtual reality experience for exploring new worlds, enjoying entertainment with your own personal cinema and gaming.

Well suited to Daydream, Tango, and other mobile applications, ST’s 6-axis IMU, which integrates a 3-axis gyroscope and a 3-axis accelerometer, enables “always-on” sensing that maximizes battery life to stay on. The IMU’s efficient power-management techniques include an enhanced gyroscope design, energy-efficient data batching, and ST’s ultra-low-power process technology.

“Certification of ST’s 6-axis motion-sensing device for operation with Daydream and Tango for amazing virtual- and augmented-reality experiences demonstrates our abilities to design and deliver an exceptionally accurate and power-efficient IMU,” said Aymeric Gisselbrecht, Vice President Global Key Accounts Sales, STMicroelectronics. “Our long-term developments in sensing and actuation, along with our work with Google, are contributing to making mobile applications incredibly immersive and even more fun.”

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