̽��ֱ�� of Cambridge - plastic electronics

Plastic crystals hold key to record-breaking energy transport

sc604 — Thu, 24 May 2018 18:00:00 +0000

̽��ֱ��researchers, whose work appears in the journal Science, say their findings could be a “game changer” by allowing the energy from sunlight absorbed in these materials to be captured and used more efficiently.

Lightweight semiconducting plastics are now widely used in mass market electronic displays such as those found in phones, tablets and flat-screen televisions. However, using these materials to convert sunlight into electricity to make solar cells is far more complex.

̽��ֱ��photo-excited states – when photons of light are absorbed by the semiconducting material – need to move so that they can be “harvested” before they lose their energy. These excitations typically only travel about 10 nanometres in plastic (or polymeric) semiconductors, so researchers need to build tiny structures patterned at the nanoscale to maximise the “harvest”.

Dr Xu-Hui Jin and colleagues at the ̽��ֱ�� of Bristol developed a new way to make highly ordered crystalline semiconducting structures using polymers.

Dr Michael Price of Cambridge's Cavendish Laboratory measured the distance that the photo-exited states travelled, which reached distances of 200 nanometres – 20 times further than was previously possible.

200 nanometres is especially significant because it is greater than the thickness of material needed to completely absorb ambient light, making these polymers more suitable as “light harvesters” for solar cells and photodetectors.

“ ̽��ֱ��gain in efficiency would actually be for two reasons: first, because the energetic particles travel further, they are easier to “harvest”, and second, we could now incorporate layers around 100 nanometres thick, which is the minimum thickness needed to absorb all the energy from light – the so-called optical absorption depth,” said co-author Dr George Whittell from the ̽��ֱ�� of Bristol. “Previously, in layers this thick, the particles were unable to travel far enough to reach the surfaces.”

“ ̽��ֱ��distance that energy can be moved in these materials comes as a big surprise and points to the role of unexpected quantum coherent transport processes,” said co-author Professor Sir Richard Friend from Cambridge's Cavendish Laboratory, and a Fellow of St John's College.

̽��ֱ��research team now plans to prepare structures thicker than those in the current study and greater than the optical absorption depth, with a view to building prototype solar cells based on this technology.

They are also preparing other structures capable of using light to perform chemical reactions, such as the splitting of water into hydrogen and oxygen.

Reference:
Xu-Hui Jin et al. ‘Long-range exciton transport in conjugated polymer nanofibers prepared by seeded growth.’ Science (2018). DOI: 10.1126/science.aar8104

Adapted from a ̽��ֱ�� of Bristol press release.

Scientists from the Universities of Cambridge and Bristol have found a way to create plastic semiconductor nanostructures that absorb light and transport its energy 20 times further than has been previously observed, paving the way for more flexible and more efficient solar cells and photodetectors.

̽��ֱ��distance that energy can be moved in these materials comes as a big surprise.

Richard Friend

̽��ֱ�� of Bristol

Image showing light emission from the polymeric nanostructures and schematic of a single nanostructure

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Cambridge Graphene Centre and Plastic Logic announce partnership

tdk25 — Wed, 26 Jun 2013 11:30:40 +0000

A formal collaboration between Cambridge’s Graphene Centre, and the ̽��ֱ�� spin-out company, Plastic Logic, has been announced.

Plastic Logic will work with Cambridge researchers on a specific programme which aims to exploit graphene, related two dimensional materials and hybrid systems in flexible, plastic electronics - a field in which the UK already enjoys a world-leading position.

̽��ֱ��agreement brings together two nerve-centres of technology research in Cambridge. Plastic Logic, founded in 2000, is a spin-off company from the ̽��ֱ��’s Cavendish Research Laboratory, and develops and manufactures colour and monchrome plastic, flexible displays. ̽��ֱ��market for these devices is expected to be worth $40bn by 2020.

̽��ֱ��Cambridge Graphene Centre was established earlier this year to captalise on the ̽��ֱ��’s ground-breaking research into the new material of the same name as well as a large class of related layered materials and hybrids. Graphene is a one atom-thick layer of graphite with remarkable potential to enable significant technological advances. ̽��ֱ��research of the Centre aims to find ways of manufacturing and optimising graphene and related materials so that this promise can become reality.

Plastic Logic has donated large-scale depositon equipment to the Centre to support the progression of new developments in graphene research. ̽��ֱ��research programme itself will investigate the development of graphene as a transparent, conductive layer within flexible displays, and of novel transistor structures using layered materials, which promise to significantly improve the performance of flexible electronics.

Professor Andrea Ferrari, Director of the Cambridge Graphene Centre, said: “ ̽��ֱ��mission of our centre is to investigate the science and technology of graphene, carbon allotropes, layered crystals and hybrid nanomaterials. ̽��ֱ��engineering innovation centre allows our partners to meet and effectively establish joint industrial-academic activities to promote innovative and adventurous research with an emphasis on applications.”

“We welcome Plastic Logic as one of our strategic partners. Graphene and related materials are ideally suited for applications in flexible electronics and this strong synergy with a world-leading Cambridge-based company can accelerate exploitation.”

Indro Mukerjee, CEO of Plastic Logic, said: “I am delighted that Plastic Logic is working with the world-class team at the Cambridge Graphene Centre on this transformational research programme for the application of graphene in our flexible plastic electronics process. This will enable higher levels of customisation and drive a step change in technology performance, opening up new commercial applications, such as the huge potential market for large area distributed sensors.”

̽��ֱ�� spin-out will work with the newly-established Cambridge Graphene Centre.

Graphene and related materials are ideally suited for applications in flexible electronics.

Andrea Ferrari

Wikimedia Commons.

Graphene.

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Plastic electronics: a neat solution

amb206 — Mon, 09 Apr 2012 08:43:56 +0000

̽��ֱ��sense of touch is something we take for granted. ̽��ֱ��sensitive nerves in our finger tips generate a flow of information to our brains that enables us to do things that require extraordinary precision. Reaching out for an object in the darkness, we are able to tell in a split second what we’re touching and how to respond. Artificial skin with the ability to process information – such as texture and temperature - has long been the holy grail of researchers working on the next generation of electronics. Artificial skin, which has potential in areas such as robotics, and other products are now within our grasp as the result of recent research into the exciting field of plastic electronics.

Initially discovered in the late 1970s, plastic electronics is an expanding technology that is bringing us a myriad of products incorporating flexible and transparent electronic circuits in which the active materials are deposited as printable inks onto polymer-based substrates using various printing technologies. Rather than relying on conventional, rigid and brittle silicon chips to process information, plastic technology relies on novel organic materials which can be printed, just as coloured inks can be printed on paper. Plastic electronic circuits have the potential to be printed in a small laboratory containing one or two printing tools, whereas state-of-the-art microchip factories are about the size of three football fields and require purpose-built facilities.

However, the full commercial potential of plastic electronic circuits has been hampered by their lower speed and by the requirement of high supply voltage (of the order of 100 V), which meant that they were unable to compete with conventional silicon-based electronics especially in off-the-grid applications, which are the most attractive for this technology.

A breakthrough by researchers at the ̽��ֱ�� of Cambridge’s Cavendish Laboratory lays the foundation for plastic electronic circuits that are fast, flexible and have low power consumption – as well as being cheap and relatively straightforward to produce. Physicists Dr Auke Kronemeijer and Dr Enrico Gili, working in the Cambridge team led by Professor Henning Sirringhaus, have developed a technology based on solution-processed organic semiconductors that will find a wide range of applications in everyday life – from radio frequency identification (RFID) tags on supermarket packaging to transparent displays embedded in car windscreens displaying vehicle speed or satellite navigation directions.

Put simply, the new technology provides a simpler way to fabricate plastic electronic circuits with relatively high performance. Dr Kronemeijer said: “Our research shows that it’s possible to produce electronic circuits using a new class of ambipolar organic materials that simplify considerably the fabrication process compared with more traditional materials. Typically, to fabricate high performance plastic electronic circuits you need two different active materials. Our technology obtains the same result using only one material. This is an ink that can be printed and requires little more than room temperature to reach its peak performance. Conventional silicon chips, on the other hand, typically require more than 1000degC to be fabricated. ̽��ֱ��robustness and flexibility of our new material opens up the possibility for developing all kinds of intelligent products such as clothing items that interact with their wearer.”

Countless reports have predicted a future in which we will enjoy roll-up TV screens in our homes and buy phones with rollable display screens. But so far, these products have been restricted by the reliance of plastic electronics on high voltage power supplies which makes them cumbersome and impractical. Typically such circuits would operate at a speed of a few hundred Hz and would require input voltages of several dozens of volts – while the consumer would expect the devices to have embedded printed batteries able to supply all the power needed. ̽��ֱ��new circuits developed by Drs Kronemeijer and Gili exhibited the fastest operation published to date using this class of materials (a few hundred KHz) and reduced the power supply requirements by approximately one order of magnitude so that they can already be operated using a standard 9 V battery.

̽��ֱ��physicists are confident that they will be able to reduce the power supply requirements further to make this technology suitable for ubiquitous electronic devices incorporating printed power supplies. This was achieved by using new ambipolar organic materials developed by Dr Martin Heeney’s team at Imperial College, London, exhibiting carrier mobility in excess of 1 cm²/Vs. Moreover, these materials conduct both electron and holes, making the use of two different materials (such as in complementary logic circuits) redundant.

̽��ֱ��integration potential of the new technology will open up possibilities for the production of entirely new products as well as lighter, more flexible versions of existing products. Dr Gili explained: “Take an item such as a hand held solar powered calculator. This requires several discrete components contained in a bulky casing, such as a solar cell, back-up battery, silicon chip and LCD display. Using plastic electronic technology, all these components could be integrated on a single plastic substrate by simply printing different inks in different areas. Moreover, the end result would be a transparent piece of flexible plastic performing similar operations to the original, bulky calculator. Although the circuitry may not be powerful enough to perform very complex calculations, this opens up a multitude of novel applications, such as interactive playing cards or self-powered customisable business cards.”

Forty years after the introduction of microchips which have revolutionised our life with consumer products such as computers, mobile phones and TVs, it’s hard to remember a world without them. Will this new generation of plastic electronics replace the technologies used in the day-to-day products that we have come to rely on? Dr Gili said: “ ̽��ֱ��new technology has broad applications in areas such as display technology and ubiquitous sensor networks. It is not likely to replace silicon chips in computational-hungry applications such as PCs, but is has the potential to open up a whole new range of exciting applications of plastic electronics which will be cheaper and easier to manufacture, flexible and easy to customise.”

This research was published in March 2012 in the journal Advanced Materials (Vol. 24, No. 12, pp. 1558-1565) and was funded by the Engineering and Physical Sciences Research Council (EPSRC) and by the Cambridge Integrated Knowledge Centre (CIKC).

A breakthrough in the development of a new generation of plastic electronic circuits by researchers at the Cavendish Laboratory brings flexible and transparent intelligent materials – such as artificial skin and interactive playing cards - a step closer.

Plastic electronic circuits have the potential to be printed in a small laboratory containing one or two printing tools.

Enrico Gili

Printed electronic test circuit manufactured on a flexible plastic substrate at the Cavendish Laboratory, ̽��ֱ�� of Cambridge

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