Organic electronics
Organic electronics, or plastic 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 which relies on inorganic conductors such as copper or silicon.
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.
For a history of the field, see "An Overview of the First Half-Century of Molecular Electronics" by Noel S. Hush, Ann. N.Y. Acad. Sci. 1006: 1–20 (2003).
The men principally credited for the discovery and development of highly-conductive organic polymers (at least of the rigid-backbone "polyacetylene" class) are Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa, who 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.[1]
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.
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 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 [3]
Their material also incidentally demonstrated "negative differential resistance", now a hall-mark of such materials. A contemporary news article in the journal Nature 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[2], was "too early" [4] 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.
In the news
See also
References
- ^ McGinness, J.E., Mobility gaps: a mechanism for band gaps in melanins Science. 1972 Sep 8;177(52):896-7
- ^ McGinness, J.E., Mobility gaps: a mechanism for band gaps in melanins Science. 1972 Sep 8;177(52):896-7
- ^ Science, vol 183, 853-855 (1974)
- ^ "An Overview of the First Half-Century of Molecular Electronics" by Noel S. Hush, Ann. N.Y. Acad. Sci. 1006: 1–20 (2003).
External links
- Hari Singh Nalwa (2008), Handbook of Organic Electronics and Photonics (3-Volume Set), American Scientific Publishers. ISBN 1-58883-095-0
- International Symposium on Flexible Organic Electronics, 9-11 July 2008, Halkidiki, Greece
- Lab for Thin Films Nanosystems & Nanometrology (LTFN), Thessaloniki, Greece
- Organic Electronics Group, Åbo Akademi University, Finland
- Olle Inganas research group at Linkoping university
- News on organic and printed electronics
- News on organic semiconductors, organic electronics and printed electronics
- Organic electronics group in UC Berkeley
- Organic electronics group at Linköping University, Sweden
- Organic Nano Device Laboratory at National University of Singapore
- The Organic Photonics and Electronics Group at Umea University, Sweden
- Organic Electronics Association