̽��ֱ�� of Cambridge - silicon

10 quadrillionths of a second to extraction: Researchers set time limit for ultrafast perovskite solar cells

tdk25 — Thu, 21 Sep 2017 10:00:16 +0000

̽��ֱ��study, which investigated photovoltaic devices based on a type of materials called perovskites, suggests that these could achieve unprecedented levels of super-efficiency. But to do so, they will need to turn sunlight into electrons and then extract these as electrical charge within just quadrillionths of a second – a few “femtoseconds”, to give them their scientific name.

Moving electrons at this ultrafast rate would enable the creation of “hot carrier” cells. These are solar cells which can generate electricity more efficiently by making use of the added kinetic energy that electrons have for a brief moment just after they are created, while they are moving at high speed.

̽��ֱ��amount of electrical energy that can be extracted from a hot carrier cell, relative to the amount of light absorbed, could potentially match or even break an energy efficiency rate of 30%. In rough terms, this is the maximum energy efficiency that solar cells can conceivably achieve – although standard silicon cells typically have efficiencies closer to 20% in practice.

Despite the minuscule fractions of time involved, the authors of the new paper say that it is possible that perovskites could ultimately push this efficiency barrier.

̽��ֱ��study, published in the journal Nature Communications, was carried out by academics in Italy and the UK. ̽��ֱ��British team involved researchers in the Cavendish Laboratory’s Optoelectronics research group of Professor Sir Richard Friend, a Fellow of St John’s College, Cambridge. ̽��ֱ��Italian team are based at the Politecnico di Milano in the group of Professor Guilio Cerullo.

Johannes Richter, a PhD student in the Optoelectronics group and the paper’s lead author, said: “ ̽��ֱ��timescale that we calculated is now the time limit that we have to operate within if we want to create super-efficient, hot carrier solar devices. We would need to get electrons out before this tiny amount of time elapses.”

“We are talking about doing this extremely quickly, but it’s not impossible that it could happen. Perovskite cells are very thin and this gives us hope, because the distance that the electrons have to cover is therefore very short.”

Perovskites are a class of materials which could before long replace silicon as the material of choice for many photovoltaic devices. Although perovskite solar cells have only been developed within the past few years, they are already almost as energy-efficient as silicon.

Partly because they are considerably thinner, they are much cheaper to make. While silicon cells are about a millimetre thick, perovskite equivalents have a thickness of approximately one micrometre, about 100 times thinner than a human hair. They are also very flexible, meaning that in addition to being used to power buildings and machines, perovskite cells could eventually be incorporated into things like tents, or even clothing.

In the new study, the researchers wanted to know for how long the electrons produced by these cells retain their highest possible levels of energy. When sunlight hits the cell, light particles (or photons), are converted into electrons. These can be drawn out through an electrode to harvest electrical charge.

For a brief moment after they are created, the electrons are moving very quickly. However, they then start to collide, and lose energy. Electrons which retain their speed, prior to collision, are known as “hot” and their added kinetic energy means that they have the potential to produce more charge.

“Imagine if you had a pool table and each ball was moving at the same speed,” Richter explained. “After a certain amount of time, they are going to hit each other, which causes them to slow down and change direction. We wanted to know how long we have to extract the electrons before this happens.”

̽��ֱ��Cambridge team took advantage of a method developed by their colleagues in Milan called two dimensional spectroscopy. This involves pumping light from two lasers on to samples of lead iodide perovskite cell in order to simulate sunlight, and then using a third “probe” laser to measure how much light is being absorbed.

Once the electrons have collided and slowed down, and are thus starting to take up space in the cell, the amount of light being absorbed changes. ̽��ֱ��time it took for this to happen in the study effectively allowed the researchers to establish how much time is available to extract electrons while they are still “hot”.

̽��ֱ��study found that electron collision events started to happen between 10 and 100 femtoseconds after light was initially absorbed by the cell. To maximise energy efficiency, the electrons would thus need to reach the electrode in as little as 10 quadrillionths of a second.

̽��ֱ��researchers are nonetheless optimistic that this might be possible. As well as taking advantage of the intrinsic thinness of perovskite, they believe that nanostructures could be created within the cells to reduce further the distance that the electrons need to travel.

“That approach is just an idea for now, but it is the sort of thing that we would require in order to overcome the very small timescales that we have measured,” Richter added.

̽��ֱ��paper, Ultrafast carrier thermalization in lead iodide perovskite probed with two-dimensional electronic spectroscopy, is published in Nature Communications.

Researchers have quantified the astonishingly high speeds at which future solar cells would have to operate in order to stretch what are presently seen as natural limits on their energy conversion efficiency.

̽��ֱ��timescale that we calculated is now the time limit that we have to operate within if we want to create super-efficient, hot carrier solar devices.

Johannes Richter

Credit: James Cridland, via Flickr

̽��ֱ��GLA building’s solar panels. Perovskite solar cells are already challenging the energy-efficiency of silicon cells such as these.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Licence type:

Attribution

Gone in 45 nanoseconds – but a new opportunity for quantum control?

tdk25 — Mon, 22 Dec 2014 04:42:05 +0000

A new study has successfully measured the coherence of electron spin – the period of time in which the particle’s elusive quantum state can be read and manipulated – for an electron trapped in conditions that could form the basis of a future quantum internet.

̽��ֱ��study, reported in the journal Physical Review Letters, was carried out by researchers at the Universities of Cambridge and Saarbrücken. It reveals the coherence time of an electron trapped in a silicon-based colour centre within a microscopic fragment of diamond. This is a gap, manufactured inside the diamond’s lattice structure, and designed to snare an electron so that it can be manipulated.

At just 45 nanoseconds, the time period for which the electron’s spin is visible seems a miniscule fraction, but for scientists trying to bring this under control, it is, in relative terms, an age.

̽��ֱ��“spin” of a particle is its intrinsic angular momentum and can point either up or down. Physicists at numerous leading research universities, including Cambridge, are currently engaged in research which is trying to utilise spin to develop advanced quantum technologies.

In the future, electron spin could be used to represent data and move large amounts of information much faster than is currently possible. This means that better control of spin might well underpin future computing, enable the creation of an entirely new quantum network (or quantum internet), and provide the foundations for a huge range of other technologies, such as advanced sensing devices.

One problem that hinders scientists who are attempting to gain greater command over electron spin for this purpose, however, is that spins in solids cannot be seen, or manipulated, for very long. After a tiny fraction of a second has passed, the spin’s quantum state decays beyond the point of visibility. Therefore, it needs to be retained for long enough for information about the spin to be registered and manipulated.

In the new study, the researchers successfully demonstrated the extent of the coherence of an electron trapped in a “silicon-vacancy” – an impurity in the lattice of carbon atoms that make up diamond. A silicon-vacancy centre provides highly promising conditions for the manipulation of electron spin.

Building on previous research, the researchers put the electron into a “superposition” state, using a technique which involves targeting it with two lasers with carefully-tuned frequencies. In this quantum state, the spin of the electron is potentially both up and down, and it is useful because it provides a basic position from which they can then observe and measure changes using laser pulses. ̽��ֱ��vision for future spin-based technologies involves creating chains of electrons whose spin will change relative to one another based on this initial superposition concept.

When applied to the electron in the silicon vacancy centre, the method achieved a coherence period of tens of nanoseconds – a fraction of time which, for scientists trying to control spin, is actually ample.

Dr Mete Atature, a researcher at the Cavendish Laboratory and St John’s College, ̽��ֱ�� of Cambridge, who led the study with Professor Christoph Becher in Saarbrcüken, said: “This is incremental research, but it essentially deals with the elephant in the room for these colour centres, which was whether there was long-living coherence for the electron spin or not, and whether we had time to see its quantum state?”

“Arguably this is the most pressing challenge for these colour centres right now. We established that we can not only access the electron spin states, but also sustain an arbitrary superposition of them for 45 nanoseconds. When you bear in mind that it will take us picoseconds to execute laser-based operations to manipulate the spin, it becomes clear that just a fraction of this period is required. So this gives us a lot of possibilities to work with.”

̽��ֱ��vacancy centre was created by substituting a silicon atom and a gap in place of two neighbouring carbon atoms in the carbon lattice of a fragment of diamond. Research earlier this year showed that a silicon-based vacancy has the potential to be used for this purpose because the photons – or light particles – emitted by an electron trapped in such conditions are sufficiently bright, and on a sufficiently narrow bandwidth, to be attractive for various applications. ̽��ֱ��research adds to a growing realisation among scientists that silicon-vacancy centres could provide advantageous conditions for spin and photon control, simultaneously.

“Now we know that silicon vacancies provide an alternative colour centre that has spin coherence, optical detectability and superior optical qualities,” Atature added. “ ̽��ֱ��next challenge is to see if we can extend this spin coherence time by various techniques and, in parallel, see if we can entangle the spin with a single photon with sufficiently high fidelity.”

In a breakthrough study scientists have revealed the coherence, or the visibility lifespan, of the spin of an electron in an emerging colour centre in diamond. This could provide a potential component for future quantum networks.

We established that we can not only access the electron spin states, but also sustain an arbitrary superposition of them for 45 nanoseconds. When you bear in mind that it will take us picoseconds to execute laser-based operations to manipulate the spin, it becomes clear that just a fraction of this period is required.

Mete Atature

Atomic structure of the SiV- color center, consisting of an Si impurity (red) situated on an interstitial position along the bond axis and surrounded by a split-vacancy (transparent) and the next-neighbor carbon atoms (grey).

̽��ֱ��text in this work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page. For image rights, please see the credits associated with each individual image.

Yes

Bright future for British solar company

bjb42 — Thu, 16 Sep 2010 00:00:00 +0000

Cambridge Enterprise, the ̽��ֱ�� of Cambridge’s commercialisation office, and the Carbon Trust have announced the launch of Eight19 Limited, a new solar energy company which will develop and manufacture high performance, lower cost plastic solar cells for high-growth volume markets.

Spun-out from the Carbon Trust's Cambridge ̽��ֱ��-TTP Advanced Photovoltaic Research Accelerator, this latest commercial phase will focus efforts on developing product prototypes, backed by a £4.5m investment from the Carbon Trust and leading international specialty chemicals company Rhodia.

Eight19, so called as it takes 8 minutes and 19 seconds for light to travel from the sun to the earth, has been created in partnership with Professor Sir Richard Friend, Professor Henning Sirringhaus and Professor Neil Greenham of Cambridge's internationally renowned Cavendish Laboratory, and technology development company TTP.

With improvements in efficiency and lifetime, breakthroughs in organic photovoltaic technology could provide solar power at a price substantially lower than that offered by 1st and 2nd generation technologies for certain applications, which could open up new markets for solar.

Eight19's focus on the low cost potential of solar cells made with semiconducting plastics (also known as organic photovoltaics, or OPV) is built on the Cavendish Laboratory's capability to develop techniques for fabricating large scale plastic electronic devices on flexible materials using roll-to-roll processes. ̽��ֱ��company will continue to be actively engaged with the Cavendish and its innovative research output.

̽��ֱ��market for organic solar cells has the potential to reach $500 million by 2015 and to grow four fold to $2 billion by 2020 (Nanomarkets, 2009) driven by applications such as building-integrated photovoltaics, and could save up to 900 million tonnes of CO2 by 2050 - some 1.5 times the UK's current annual emissions.

̽��ֱ��Eight19 team is pursuing a design-for-manufacture strategy that focuses on the unique attributes of organic photovoltaics, combining both specific product performance characteristics and low cost of energy.

Unlike other more familiar thin film solar platforms, organic solar cells are not inherently limited by constraints around material supply and toxicity, and benefit from a number of fundamental advantages including potentially very low cost production enabled by low temperature and high throughput processing typical of plastic films. Organic solar cells potentially deliver further value throughout the supply chain, from ease of installation for construction companies to producers seeking simplified manufacturing integration.

Dr Robert Trezona, Head of R&D at the Carbon Trust said, " ̽��ֱ��launch of Eight19 and the deployment of low cost organic solar cells could help to revolutionise solar power production by opening up new markets. Cost reduction through the development of advanced technology and innovative design are key to driving forward mass production and making solar power more affordable."

"This investment is perfectly in line with our strategy to explore new promising market segments fitting with our sustainable development commitment. Furthermore, we are convinced that open innovation is key to leverage our research and development capability. We are happy to work in close partnership with prominent scientists to develop this breakthrough technology", explains Pascal Juery, Group Executive Vice-President of Rhodia.

Professor Sir Richard Friend, Co-founder of Eight19 commented, "This represents a great opportunity to transfer new technology out of the university, based on recent advances in fundamental science. Solar cells made with organic semiconductors work very differently to those made with silicon and are closer in operating principle to photosynthesis in green plants."

A world class management team underpins the technology development, with significant track record in making low cost applications using scalable roll-to-roll technology. Co-founder and Board Director Professor Sir Richard Friend is a world expert who pioneered the study of the electronic properties of a class of plastics called conjugated polymers and revolutionised the understanding of using these materials to make plastic semiconductors. He also previously co-founded Cambridge Display Technology (CDT) and Plastic Logic.

Solar energy company to develop and manufacture high performance, lower cost plastic solar cells.

Solar cells made with organic semiconductors work very differently to those made with silicon and are closer in operating principle to photosynthesis in green plants.

Professor Sir Richard Friend, Co-founder of Eight19

Clearly Ambiguous from Flickr

Solar Mosaic

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes

Plastic Logic: from innovation to impact

bjb42 — Sat, 01 Aug 2009 00:00:00 +0000

̽��ֱ��path from innovation to impact can be long and complex. Here we describe the fascinating story behind the development of a new type of electronic reader.

̽��ֱ��story of Plastic Logic started in the mid-1980s when Professor Sir Richard Friend – then a lecturer in the Department of Physics at the ̽��ֱ�� of Cambridge – began to work on organic semiconductors [see Glossary below]. ‘My interest was pure curiosity,’ says Friend, who is now the Cavendish Professor of Physics at the ̽��ֱ�� of Cambridge. He was interested, he explains, in gaining a basic understanding of how electrons might be made to move in carbon-based semiconductors, rather than being driven by the prospect that his research might be commercially useful.

Semiconductors – materials that conduct electricity under some conditions but not others – are used to make the integrated circuits that run computers and other electronic devices. Silicon is the best known semiconductor but, in the 1960s, researchers discovered that some organic molecules also behave as semiconductors. Specifically, small molecules that contain carbon atoms linked by alternating single and double bonds – so-called conjugated molecules – behave as semiconductors because some of their electrons are delocalised and ‘shared’ throughout the molecule. Friend wanted to know whether polymers made from building blocks of conjugated molecules would also behave as semiconductors. ‘We were interested in this type of molecule because we thought that, if they did behave as semiconductors, we might be able to use them to make electronic devices simply by dissolving the polymers in a solvent and then painting them onto a surface,’ says Friend.

By 1988, Friend’s research group had managed to make a transistor from the conjugated polymer polyacetylene. But, notes Professor Henning Sirringhaus, Hitachi Professor at the ̽��ֱ�� of Cambridge and Friend’s colleague since 1997, ‘the performance of this polymer or plastic transistor was very poor because the speed at which electrons and holes move through polyacetylene – a property called mobility – is much lower than in silicon. Plastic transistors were pretty much a scientific curiosity at that point, although they did provide a useful device for studying the electrical properties of new materials.’

A serendipitous discovery

Friend’s team now started to investigate whether better transistors could be made from other conjugated polymers. ‘We thought that a poorly studied compound called poly(p-phenylene vinylene), PPV, looked promising,’ says Friend, ‘and we began a collaboration with Andrew Holmes, a natural products scientist then working in the Department of Chemistry in Cambridge, to make PPV and to use it to make transistors.’

Unfortunately, PPV was not ideal for transistors – it was too good an insulator. But rather than giving up on PPV, the researchers decided to measure its insulating properties. ‘Instead of making a parallel electrode arrangement as we do for transistors, in February 1989 we made a stacked electrode arrangement as we do in diodes and sandwiched the PPV between the two electrodes to measure its insulating abilities,’ explains Friend.

By good fortune, Dr Jeremy Burroughes, who had made the first polyacetylene transistors while a PhD student in Friend’s laboratory, used a thin, semi-transparent layer of aluminium to make the top electrode in this PPV-containing device. When Burroughes (who is now the Chief Technology Officer at Cambridge Display Technology, CDT) applied a voltage to the device, he unexpectedly saw green light coming through the electrode. Friend immediately contacted Dr Richard Jennings (Director of Technology Transfer and Consultancy Services, Cambridge Enterprise Ltd) in what was then the ̽��ֱ��’s industrial liaison office to tell him about the strange, light-emitting piece of plastic and to ask for advice on patenting this discovery.

‘As soon as Richard explained what he had seen, we began to think about applications,’ says Jennings. ‘Plastic light-emitting displays, light-emitting clothing, plastic TV screens – it didn’t take much imagination to see how these polymer light-emitting diodes [P-LEDs] might be used and my advice was to patent the invention immediately.’ A particular appeal of light-emitting plastics, say both Friend and Jennings, was that these materials could be solution-processed or painted over a large area, a much simpler process than that needed to make liquid crystal displays (LCDs), the up-and-coming display technology in the late 1980s.

Patents for P-LEDs were filed in April 1989 and April 1990. Then, in October 1990, the researchers published a letter in the journalNatureentitled ‘Light-emitting diodes based on conjugated polymers’. ‘ ̽��ֱ��rest of the world simply dived in after we published. We had scores of imitators and our patent was challenged on several occasions,’ says Friend.

But, despite the academic interest in P-LEDs, Friend failed to find a UK electronics company to license and develop the invention. ‘It wasn’t that the companies weren’t willing to license the patent,’ stresses Friend. ‘It was more that they did not see organic light-emitting diodes as a core business and I was concerned that they would simply sit on our idea and not do the work needed to develop it. ̽��ֱ��quickest single way to kill a good idea is to put it into the wrong hands,’ comments Friend.

So, in 1992, Friend, with help from the ̽��ֱ�� of Cambridge and local seed venture capital, founded CDT. Although the original intention was that CDT would be a materials manufacturing company, CDT has concentrated on developing new technologies and licensing them to other companies. For example, in association with various industrial partners, CDT has developed a method to make P-LED displays using inkjet printing, thin-film transistors to stimulate the P-LED-containing pixels in displays, and polymers that emit red or blue light when stimulated instead of green light. In 2004, CDT was floated on the NASDAQ National Market and, in 2007, it was acquired by the Sumitomo Chemical Company, which maintains substantial R&D activity in and around Cambridge.

Importantly, says Friend, a strong symbiotic relationship has developed between CDT and the scientists working in the ̽��ֱ��: ‘Over the years, we have sent a lot of ideas to CDT but in return we have had access to the materials and methods that CDT has developed and this has helped us to push our fundamental research along much faster than would have been possible if we had had to do everything in the ̽��ֱ��.’

Back to transistors

While P-LEDs were being developed, some work continued in Cambridge and elsewhere on plastic transistors. Because silicon-based transistors were so good, explains Sirringhaus, ‘there wasn’t any commercial drive to work on plastic transistors and probably fewer than ten groups worldwide were working on the problem.’ Adds Friend, ‘it was really a matter of waiting for new materials to be made, waiting for the technology and science to develop to a stage where we could take the transistors forward.’

Then, in 1997, a way was found to increase the mobility of polymer semiconductors. ̽��ֱ��problem with the original polymer semiconductors had been that the long-chain molecules within these substances were disordered – ‘like a bowl of spaghetti’, says Sirringhaus. As the charge moved through this disordered mass, it encountered configurations where it didn’t know where to go and this reduced the material’s mobility. ̽��ֱ��polymer chains were disordered because, to process polymer solutions,

flexible side chains have to be attached to the polymer chains. Unfortunately, these side chains made the polymer disordered and electrically poorly conducting. ̽��ֱ��1997 breakthrough was the discovery of a way to deposit materials from polymer solutions that consist of alternating layers of conjugated polymers lying in a plane and insulating side chains. ‘ ̽��ֱ��mobility in the conjugated plane can be very high and it doesn’t matter about the mobility elsewhere in the structure,’ explains Sirringhaus.

Although the demonstration that the mobility of polymer semiconductors could rival that of inorganic semiconductors like silicon was important, before the researchers could persuade large companies or venture capitalists to invest time and/or money in their discovery, they still had to show that their new material could be used to make transistors in a practical manner.

‘At that time, we were developing methods to use inkjet printing to deposit P-LEDs onto substrates so we started to investigate whether the same process could be used to print transistors,’ says Sirringhaus. Within a few months, Sirringhaus and PhD student Takeo Kawase, on secondment from Seiko Epson, had printed a few transistors onto small substrate chips and had shown that these simple circuits performed reasonably well. ‘We now had a credible story on the materials and a credible way to make devices from them so we began to think about commercialisation,’ says Sirringhaus. Indeed, says Friend, ‘I had a strong sense that the future seminal events in the development of organic transistors were going to be engineering events, not science events, and I believed that these were most likely to happen in a well-focused industrial environment.’

Plastic Logic is founded

With this in mind, the researchers approached the entrepreneur and venture capitalist Dr Hermann Hauser, a co-founder of Amadeus Capital Partners (Cambridge) and an early investor in CDT, to see whether he would invest money in the commercial development of organic polymer transistors.

‘I remember visiting Richard and his group in the Cavendish,’ says Hauser. ‘They only had a few transistors working at this time [1998] and when they stopped working they prodded them with toothpicks!’ Luckily, Hauser, with his background in physics and interest in electronics, instantly recognised that Friend, Sirringhaus and their colleagues had made a very fundamental breakthrough and, with his help, Plastic Logic was formed in January 2000.

What is so special about plastic transistors?

When Plastic Logic started, all the electronic displays in the world were made on glass. Displays like those attached to computers contain millions of pixels, each of which is switched on and off by an individual silicon transistor. To produce these transistors, amorphous (non-crystalline) silicon is processed at high temperatures. Consequently, silicon-based transistors can only be produced on a substrate like glass that can withstand high temperatures; a plastic substrate would melt or deform. But displays that contain glass are heavy, rigid and fragile and unsuitable for use in anything but very small mobile displays. ̽��ֱ��production of plastic transistors, by contrast, does not require high temperatures so they can be laid down on plastic substrates that are much lighter, and more flexible and robust than glass. This means that large portable displays can be made by using plastic instead of silicon transistors.

Plastic transistors have a second advantage over silicon transistors when it comes to making large displays. Electronic circuits contain many layers that have to be accurately aligned with each other. In a large display, the dimensions of the substrate inevitably change slightly during the production process. Silicon-based displays are made using a lithographic process in which patterns are sequentially deposited onto substrates using metal masks. Unfortunately, any small changes in the dimensions of the substrate during the production process mean that the masks do not line up accurately and the resultant display is defective. With displays that contain plastic transistors, computers drive the inkjet printers that make the various layers of the device so it is possible to allow for changes in the substrate’s dimensions.

From single transistors to an electronic reader

‘When Plastic Logic was founded,’ says Jennings, ‘there wasn’t a clear business plan but Hermann Hauser was a very far-sighted investor who, knowing the track record of Richard Friend and Henning Sirringhaus, was willing to put money into their company to see where it would go.’ Over the next few years, Plastic Logic raised considerable sums of money to support its work and by 2006 it had developed its plastic transistor technology sufficiently to produce a display containing a million transistors. It had also developed an application for these displays – a plastic electronic reader. Since 2006, Plastic Logic has raised more than US$100 million to build a large manufacturing plant in Dresden (Germany); its research and development department still remains in Cambridge but its corporate headquarters is now based in Mountain View (California, USA). Trials of the electronic reader with key customers should be completed by the end of 2009 and commercial production will be rolled out in 2010.

̽��ֱ��electronic reader, which has an A4 screen that is about as heavy and thick as a sheet of paper, uses an ‘active matrix display’, an array of pixels in which each pixel contains minute plastic capsules filled with a liquid that contains black and white particles. These particles have different charges so that when an electric current is applied to a pixel, either the white or the black particles move to the front of the capsule and the pixel appears white or black. A plastic transistor behind each pixel applies the electric charges and the whole device is printed onto a thin, flexible sheet of plastic.

Plastic Logic’s electronic reader will enable users to read their own documents anywhere and will give them access to newspapers and books and, according to Friend, Sirringhaus and Hauser, it has several advantages over existing electronic readers such as Amazon’s Kindle. Its display is lighter and more robust than the glass-based displays in other readers and, because the display is bigger than those in other readers, it is more suitable for accessing newspapers. Also, the device uses very little energy because, unlike other readers, the display in the Plastic Logic reader does not need a back light. Consequently, once a page is set, it can remain in place without consuming any energy. Thus, users should be able to take a Plastic Logic reader away on holiday, for example, without having to take a battery charger.

Other hopes for plastic electronics – the need for continuing basic research

Plastic Logic should produce several hundred thousand electronic readers in 2010 and, in later years, it could be producing millions of units. But Hauser believes that plastic electronics will have much broader applications in the future. While Plastic Logic was developing its electronic reader, he explains, basic research was continuing in the ̽��ֱ�� of Cambridge, where Sirringhaus’ group recently made an important breakthrough by discovering how to make a CMOS plastic transistor.

‘CMOS’ stands for complementary metal oxide semiconductor, a type of semiconductor that can be used to produce a combined n-type and p-type transistor. This type of transistor is needed to build complex devices like computer processors but for many years it seemed that it would be impossible to build plastic transistors with the properties of CMOS transistors – polymer semiconductors were all p-type semiconductors because they all carried current in the form of holes. Then, in 2005, Sirringhaus and his colleagues showed that the reason why th

ere were no n-type polymer semiconductors was because the electrons were being trapped at the interface between the semiconductor and adjacent insulators. By studying this interface, the researchers were able to produce an n-type polymer semiconductor, which opened up the possibility of designing the CMOS circuits that are necessary for the development of a broad plastic electronics industry.

However, Friend, Sirringhaus and Hauser stress that relatively little is known about polymer semiconductors and, because these materials are so different from silicon, it is not possible to rely on established semiconductor physics to understand how they work. Thus, it is essential that fundamental research on polymer semiconductors continues to be funded within UK universities. This, together with improved governmental support for the companies involved in plastic electronics, should ensure that the UK’s current lead in the field of plastic electronics is retained and that the UK reaps the financial rewards of the groundbreaking, curiosity-driven basic research in which Friend, Sirringhaus and their colleagues excel.

Glossary

Conductor:a material that can carry an electric current.

Diode:an electronic component with two electrodes that conducts electric current in only one direction.

Insulator:a non-conductor of electric current.

Light-emitting diode (LED):a diode that emits light when current passes through it. LEDs are used in many electronic devices.

Liquid crystal display (LCD):a display technology in which a current passing through a liquid crystal solution makes the crystals line up so that light cannot pass through them.

Organic semiconductor:a carbon-based semiconductor.

Pixels:picture elements, the units from which images are made on televisions and computer monitors.

Plastic (or polymer) semiconductor:a semiconductor made from an organic polymer.

Plastic (or polymer) transistor:a transistor that contains a plastic semiconductor.

Semiconductor:a substance that conducts electricity only under some conditions. ̽��ֱ��conductivity of semiconductors can be increased by applying heat, light or a voltage. Ann-typesemiconductor carries current mainly in the form of negatively charged electrons. Ap-typesemiconductor carries current mainly as electron deficiencies calledholes; a hole has an equal and opposite electric charge to an electron.

Transistor:a semiconductor device used to amplify or switch electronic signals. A small current across one pair of terminals in a transistor controls the current at another pair of terminals, either amplifying the original current or turning the current on and off in a circuit.

̽��ֱ��path from innovation to impact can be long and complex. Here we describe the fascinating story behind the development of a new type of electronic reader.

‘Plastic light-emitting displays, light-emitting clothing, plastic TV screens – it didn’t take much imagination to see how these polymer light-emitting diodes might be used and my advice was to patent the invention immediately.’

Dr Richard Jennings

Plastic Logic

Electronic reader

A tale of two innovations

We are often taken aback by the sudden appearance of a new innovation that has clear economic or clinical impact. Just how did these innovations arise?

Academic scientists working in universities are driven to do their research for many reasons. Some see their research as a way to develop new drugs or to build more powerful computers, for example. Many academic scientists, however, are simply curious about the world around them. They may want to understand the intricacies of the immune system or how the physical structure of a material determines its properties at a purely intellectual level. They may never intend to make any practical use of the knowledge that they glean from their studies.

Importantly, however, even the most basic, most fundamental research can be the starting point for the development of materials and technologies that make a real difference to the everyday life of ordinary people and that bring economic benefit to the country. Indeed, said Dr Richard Jennings, Director of Technology Transfer and Consultancy Services at Cambridge Enterprise Ltd, ̽��ֱ�� of Cambridge, ‘what universities are good at is fundamental research and it is high-quality basic research that generates the really exciting ideas that are going to change the world.’

But it takes a great deal of time, money and commitment to progress from a piece of basic research to a commercial product, and the complex journey from the laboratory to the marketplace can succeed only if there is long-term governmental support for the academic scientists and their ideas as well as the involvement of committed commercial partners and well-funded technology transfer offices.

Two particular stories illustrate the long and complex path taken from the laboratory to commercial success by two very different ̽��ֱ�� of Cambridge innovations. In the case of Plastic Logic, basic research on materials called organic semiconductors that started in the 1980s and that continues today has led to the development of a new type of electronic reader that should be marketed in early 2010 and, more generally, to the development of ‘plastic electronics’, a radical innovation that could eventually parallel silicon-based electronics. For Campath, the journey started just before Christmas in 1979 in a laboratory where researchers were trying to understand an immunological concept called tolerance. Now, nearly three decades later and after a considerable amount of both basic research and commercial development, Campath-1H is in Phase 3 clinical trials for the treatment of relapsing–remitting multiple sclerosis.

‘Both innovations are likely to have profound impacts over the next two years and it is important to recognise the deep temporal roots of both,’ said Professor Ian Leslie, Pro-Vice-Chancellor for Research.

Professor Leslie highlighted that an important lesson to draw from these stories ‘is the need for universities and other recipients of public research funding to implement and develop processes to support the translation of discovery to impact or, more generally, to develop environments in which the results of discovery can be taken forward and in which external opportunities for innovation are understood.’

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes

‘Magic’ lights to slash household electricity use

bjb42 — Wed, 28 Jan 2009 00:00:00 +0000

̽��ֱ��new LEDs use Gallium Nitride (GaN), a man-made semiconductor that emits a brilliant bright light but uses very little electricity. Until now high production costs have made GaN lighting too expensive for widespread use in homes and offices.

̽��ֱ��Cambridge ̽��ֱ�� Centre for Gallium Nitride, with funding from the Engineering and Physical Sciences Research Council (EPSRC), has developed a new way of making GaN which could produce LEDs for a tenth of current prices.

̽��ֱ��new technique grows GaN on silicon wafers, which achieves a 50% improvement in cost and efficiency on previous approaches to grow GaN in labs on expensive sapphire wafers, used since the 1990s.

Based on current results, GaN LED lights in every home and office could cut the proportion of UK electricity used for lights from 20% to 5%. A reduction equivalent to the output of eight power stations.

A GaN LED can burn for 100,000 hours and therefore, on average, only needs replacing after 60 years. And, unlike currently available energy-saving bulbs, GaN LEDs do not contain mercury eliminating the environmental problems posed by their disposal. GaN LEDs also have the advantage of turning on instantly and being dimmable.

Professor Colin Humphreys, lead scientist on the project said: "This could well be the holy grail in terms of providing our lighting needs for the future. We are very close to achieving highly efficient, low cost white LEDs that can take the place of both traditional and currently available low-energy light bulbs. That won't just be good news for the environment, it will also benefit consumers by cutting their electricity bills."

GaN LEDs, used to illuminate landmarks like Buckingham Palace and the Clifton Suspension Bridge, are also appearing in camera flashes, mobile phones, torches, bicycle lights and interior bus, train and plane lighting.

Parallel research is also being carried out into how GaN lights could mimic sunlight to help 3m people in the UK with Seasonal Affective Disorder (SAD).

Ultraviolet rays made from GaN lighting could also aid water purification and disease control in developing countries, identify the spread of cancer tumours and help fight hospital 'super bugs'.

A new way of making LEDs could see household lighting bills reduced by up to 75% in five years time, thanks to research at Cambridge ̽��ֱ��.

We are very close to achieving highly efficient, low cost white LEDs that can take the place of both traditional and currently available low-energy light bulbs.

Professor Colin Humphreys

nao904 from Flickr

LED

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes

Affordable solar power on the horizon

tdk25 — Fri, 05 Oct 2007 00:00:00 +0000

Environmentally friendly solar panels may be an affordable alternative to conventional power sources within the next ten years, as a result of a new initiative launched this week.

̽��ֱ��project, funded by the Carbon Trust, will be led by the ̽��ֱ�� of Cambridge's Cavendish Laboratory in collaboration with ̽��ֱ��Technology Partnership.

Currently solar panels are made from silicon, which makes them expensive to manufacture and therefore cost prohibitive for many. However, new technology being researched at Cambridge uses plastic to create solar cells, a much more cost effective and energy efficient method.

̽��ֱ��scientists have already developed a small prototype solar panel that can power a calculator. ̽��ֱ��next step will be to advance this technology so that it can be easily applied on a much larger scale and ultimately be manufactured in large sheets of plastic. These sheets will be able to sit on a wide range of surfaces, including windows or building roofs, to capture solar energy. Simple applications could also include chargers for mobile telephones or laptop computers.

If the project succeeds in its aim to deploy more than 1 gigawatt of power using the new solar panels by 2017, it could deliver CO2 savings of more than 1 million tonnes per year.

Sir Richard Friend, Cavendish Professor of Physics in the ̽��ֱ�� of Cambridge, said:

"We are delighted to work with ̽��ֱ��Technology Partnership and the Carbon Trust on solar energy. This is a timely opportunity to build on technology developed in the ̽��ֱ��, and we will capitalise on the local Cambridge strengths in taking science to manufacturing."

Environmentally friendly solar panels may be an affordable alternative to conventional power sources within the next ten years, as a result of a new initiative launched this week.

We are delighted to work with ̽��ֱ��Technology Partnership and the Carbon Trust on solar energy. This is a timely opportunity to build on technology developed in the ̽��ֱ��, and we will capitalise on the local Cambridge strengths in taking science to manufacturing.

from flickr

̽��ֱ��Sun

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes