Organic electronics

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Organic electronics, plastic electronics or polymer electronics, is a branch of materials science dealing with electrically-conductive polymers and conductive small molecules. It is called 'organic' electronics because the polymers and small molecules are carbon-based. This contrasts with traditional electronics, which relies on inorganic conductors and semiconductors, such as copper and silicon, respectively. In addition to organic charge transfer complexes, examples include polyacetylene, polyaniline (PANI), and polythiophene.

Contents

History [edit]

In 1862, Henry Letheby produced a partly conductive material by anodic oxidation of aniline in sulfuric acid. The material was probably polyaniline.[1] In the 1950s, it was discovered that polycyclic aromatic compounds formed semi-conducting charge-transfer complex salts with halogens.[2] This finding indicated that organic compounds could carry current.

High conductivity of 1 S/cm was reported in 1963 for a derivative of tetraiodopyrrole.[3][4][5]

Research on conducting polymer flourished after the 1977 discovery that polyacetylene can be oxidised ("doped") with halogens to produce materials from insulating or semiconducting to highly conducting.[6] For this work, Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa were jointly awarded the Nobel Prize in Chemistry in 2000.[1]

Ching W. Tang who built the first organic light-emitting diode (OLED) and organic photovoltaic cell is widely considered the father of organic electronics.[7]

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.[8]

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.

Features [edit]

Main article: Printed electronics

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 organic 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. An example is ThinFilm's roll-to-roll printed organic memory.[9][10][11][12]

Organic electronic devices [edit]

Main articles: Organic photovoltaics, Photovoltaics, and Low cost solar cell
Organics-based flexible display

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.[13]

Silicon thin film solar cells on flexible substrates allow a significant cost reduction of large-area photovoltaics for several reasons:[14]

  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) have the potential for 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.[14]

One advantage of printed electronics is that 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.[15]

See also [edit]

References [edit]

  1. ^ a b The Nobel Prize in Chemistry, 2000: Conductive polymers, nobelprize.org
  2. ^ Herbert Naarmann “Polymers, Electrically Conducting” in Ullmann's Encyclopedia of Industrial Chemistry 2002 Wiley-VCH, Weinheim. doi:10.1002/14356007.a21_429
  3. ^ McNeill, R.; Siudak, R.; Wardlaw, J. H.; Weiss, D. E. (1963). "Electronic Conduction in Polymers. I. The Chemical Structure of Polypyrrole". Aust. J. Chem. 16 (6): 1056–1075. doi:10.1071/CH9631056. 
  4. ^ Baracus, B. A.; Weiss, D. E. (1963). "Electronic Conduction in Polymers. II. The Electrochemical Reduction of Polypyrrole at Controlled Potential". Aust. J. Chem. 16 (6): 1076–1089. doi:10.1071/CH9631076. 
  5. ^ Bolto, B. A.; McNeill, R.; Weiss, D. E. (1963). "Electronic Conduction in Polymers. III. Electronic Properties of Polypyrrole". Aust. J. Chem. 16 (6): 1090–1103. doi:10.1071/CH9631090. 
  6. ^ Inzelt, György (2008). "Chapter 1: Introduction". In Scholz, F. Conducting Polymers: A New Era in Electrochemistry. Monographs in Electrochemistry. Springer. pp. 1–6. ISBN 978-3-540-75929-4. 
  7. ^ Forrest, Stephen (June 2012). "Energy efficiency with organic electronics: Ching W. Tang revisits his days at Kodak". Cambridge Journals Online MRS Bulletin. 
  8. ^ McGinness, J.E. (1972). "Mobility gaps: a mechanism for band gaps in melanins". Science 177 (4052): 896–7. Bibcode:1972Sci...177..896M. doi:10.1126/science.177.4052.896. PMID 5054646. 
  9. ^ Thinfilm and InkTec awarded IDTechEx' Technical Development Manufacturing Award IDTechEx, April 15th 2009
  10. ^ PolyIC, ThinFilm announce pilot of volume printed plastic memories EETimes, September 22nd 2009
  11. ^ All set for high-volume production of printed memories Printed Electronics World, April 12th 2010
  12. ^ Thin Film Electronics Plans to Provide ‘Memory Everywhere’ Printed Electronics Now, May 2010
  13. ^ "Mass Production of Plastic Solar Cells". Technology Review. Retrieved 2010-02-14. 
  14. ^ a b Niedertemperaturabscheidung von Dünnschicht-Silicium für Solarzellen auf Kunststofffolien, Doctoral Thesis by Koch, Christian 2002
  15. ^ Raghu Das, IDTechEx. "Printed electronics, is it a niche? - 25 September 2008". Electronics Weekly. Retrieved 2010-02-14. 

External links [edit]

Further reading [edit]

  • An Overview of the First Half-Century of Molecular Electronics by Noel S. Hush, Ann. N.Y. Acad. Sci. 1006: 1–20 (2003).
  • Electronic Processes in Organic Crystals and Polymers, 2 ed. by Martin Pope and Charles E. Swenberg, Oxford University Press (1999), ISBN 0-19-512963-6
  • Handbook of Organic Electronics and Photonics (3-Volume Set) by Hari Singh Nalwa, American Scientific Publishers. (2008), ISBN 1-58883-095-0
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