Organic electronics

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Organic electronics, plastic electronics or polymer electronics, is a branch of electronics that deals with conductive polymers, plastics, or small molecules. It is called 'organic' electronics because the polymers and small molecules are carbon-based, like the molecules of living things. This is as opposed to traditional electronics (or metal electronics) which relies on inorganic conductors such as copper or silicon.

Polymer electronics are laminar electronics, that also includes transparent electronic package and paper based electronics ^[1].

In addition to organic Charge transfer complexes, technically, electrically conductive polymers are mainly derivatives of polyacetylene black (the "simplest melanin"). Examples include PA (more specificially iodine-doped trans-polyacetylene); polyaniline: PANI, when doped with a protonic acid; and poly(dioctyl-bithiophene): PDOT.

Contents 1 History 2 Features 3 Organic electronic devices 4 Plastic Solar Cells 5 Makers and research 5.1 Research 6 See also 7 References 8 Further reading 9 External links

[edit] History

Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa are credited for the discovery and development of highly-conductive polymers (at least of the rigid-backbone "polyacetylene" class) and were jointly awarded the Nobel Prize in Chemistry in 2000 for the 1977 discovery and development of oxidized, iodine-doped polyacetylene.

Interestingly, this prize passed over the much earlier discovery of highly-conductive organic Charge transfer complexes, some of which are even superconductive. Similarly, the first demonstration of high-conductivity in the linear backbone polymers was a series of papers by Weiss et al. [1] in 1963. These workers reported a conductivity of 1 S/cm in a similarly iodine-"doped" and oxidized polypyrrole black.

Conduction mechanisms in such materials involve resonance stabilization and delocalization of pi electrons along entire polymer backbones, as well as mobility gaps, tunneling, and phonon-assisted hopping.^[2]

Technology for plastic electronics on thin and flexible plastic substrates was developed at Cambridge University’s Cavendish Laboratory in the 1990s. In 2000, Plastic Logic was spun out of Cavendish Laboratory to develop a broad range of products using the plastic electronics technology ^[3].

[edit] Features

Conductive polymers are lighter, more flexible, and less expensive than inorganic conductors. This makes them a desirable alternative in many applications. It also creates the possibility of new applications that would be impossible using copper or silicon.

Organic electronics not only includes organic semiconductors, but also dielectrics, conductors and light emitters.

New applications include smart windows and electronic paper. Conductive polymers are expected to play an important role in the emerging science of molecular computers.

In general organic conductive polymers have a higher resistance and therefore conduct electricity poorly and inefficiently, as compared to inorganic conductors. Researchers currently are exploring ways of "doping" organic semiconductors, like melanin, with relatively small amounts of conductive metals to boost conductivity. However, for many applications, inorganic conductors will remain the only viable option.

Organic electronics can be printed.

[edit] Organic electronic devices

A 1972 paper in the journal Science ^[2] proposed a model for electronic conduction in the melanins. Historically, melanin is another name for the various oxidized polyacetylene, polyaniline, and Polypyrrole "blacks" and their mixed copolymers, all commonly-used in present day organic electronic devices. E.g., some fungal melanins are pure polyacetylene. This model drew upon the theories of Neville Mott and others on conduction in disordered materials. Subsequently, in 1974, the same workers at the Physics Department of The University of Texas M. D. Anderson Cancer Center reported an organic electronic device, a voltage-controlled switch ^[4]

Their material also incidentally demonstrated "negative differential resistance", now a hall-mark of such materials. A contemporary news article in the journal Nature ^[5] noted this materials "strikingly high conductivity'. These researchers further patented batteries, etc. using organic semiconductive materials. Their original "gadget" is now in the Smithsonian's collection of early electronic devices.

This work, like that the decade-earlier report of high-conductivity in a polypyrrole^[6], was "too early" ^[7] and went unrecognized outside of pigment cell research until recently. At the time, few except cancer research institutes were interested in the electronic properties of such polymers, which are applicable to the treatment of melanoma.

[edit] Plastic Solar Cells

Organic solar cells could cut the cost of solar power by making use of inexpensive organic polymers rather than the expensive crystalline silicon used in most solar cells. What's more, the polymers can be processed using low-cost equipment such as ink-jet printers or coating equipment employed to make photographic film, which reduces both capital and manufacturing costs compared with conventional solar-cell manufacturing. ^[8].

Silicon thin film solar cells on flexible substrates allow a significant cost reduction of large-area photovoltaics for several reasons ^[9]:

1. The so-called 'roll-to-roll'-deposition on flexible sheets is much easier to realize in terms of technological effort than deposition on fragile and heavy glass sheets.
2. Transport and installation of lightweight flexible solar cells also saves cost as compared to cells on glass.

Inexpensive polymeric substrates like polyethylene terephtalate (PET) or polycarbonate (PC) would be a way out towards further cost reduction in photovoltaics. Protomorphous solar cells prove to be a promising concept for efficient and low-cost photovoltaics on cheap and flexible substrates for large-area production as well as small and mobile applications ^[9].

One beauty of printed electronics is that the different electrical and electronic components can be printed on top of each other, saving space and increasing reliability and sometimes they are all transparent. One ink must not damage another and low temperature annealing is vital if low-cost flexible materials such as paper and plastic film are to be used. There is much sophisticated engineering and chemistry involved here, with iTi, Pixdro, Asahi Kasei, Merck, BASF, HC Starck, Hitachi Chemical and Frontier Carbon Corporation among the leaders ^[10].

G24 Innovations, Gifu University, National Chiao University are working in printed organic photovoltaics.

[edit] Makers and research

• Printed organic transistors: University of Tokyo,Sony, EPrint, Cambridge University (zinc oxide)
• Printed ferroelectric memory: Thin Film Electronics (polymer nonvolatile memory applications).
• E-paper: Bridgestone (liquid powder display technology), E Ink
• Loudspeaker film: NXT plc
• Printed organic battery: Waseda University
• Biosensors: University of California at Berkeley

[edit] Research

• Organic semiconductors: Palo Alto Research Center
• Center for Organic Photonics and Electronics=

[edit] See also

• Annealing
• Bioplastic
• Carbon nanotube
• Circuit deposition
• Conductive ink
• Disposable electronics
• Flexible display
• FMCG
• Laminar
• Melanin
• Organic semiconductor
• Organic LED
• PETEC
• Photodetector
• Plastic Logic
• Printed electronics
• Radio frequency identification
• Radio tag
• Spin coating

[edit] References

[edit] Further reading

• An Overview of the First Half-Century of Molecular Electronics by Noel S. Hush, Ann. N.Y. Acad. Sci. 1006: 1–20 (2003).
• Hari Singh Nalwa (2008), Handbook of Organic Electronics and Photonics (3-Volume Set), American Scientific Publishers. ISBN 1-58883-095-0

[edit] External links

• Organic Electronics Association
• Center for Organic Electronics
• International Plastics Electronics Conference
• BBC News - UK firm Plastic Logic has said it will build the world's first factory to produce plastic electronic chips
• Linking electronics - George Malliaras discusses the interplay between organic electronics and biology in his interview for Chemical Technology published by the Royal Society of Chemistry