Organic electronics - AbsoluteAstronomy.com

Organic electronics, plastic electronics or polymer electronics, is a branch of electronics

Electronics

Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

dealing with conductive polymers, plastics, or small molecules

Molecule

A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...

. It is called 'organic

Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

' electronics because the polymers and small molecules are carbon

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

-based. This contrasts with traditional electronics (or metal electronics), which relies on inorganic

Inorganic chemistry

Inorganic chemistry is the branch of chemistry concerned with the properties and behavior of inorganic compounds. This field covers all chemical compounds except the myriad organic compounds , which are the subjects of organic chemistry...

conductor

Electrical conductor

In physics and electrical engineering, a conductor is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons...

s such as copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

or silicon

Silicon

Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

.

Most polymer electronics are laminar electronics, a category that also includes transparent electronic package and paper based electronics.

In addition to organic charge transfer complexes, technically, electrically conductive polymer

Polymer

A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...

s are mostly derivatives of polyacetylene

Polyacetylene

Polyacetylene is an organic polymer with the repeat unit n. The high electrical conductivity discovered for these polymers beginning in the 1960's accelerated interest in the use of organic compounds in microelectronics...

black (the "simplest melanin

Melanin

Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...

"). Examples include polyacetylene

Polyacetylene

(PA; more specificially iodine

Iodine

Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....

-doped trans-polyacetylene); polyaniline

Polyaniline

Polyaniline is a conducting polymer of the semi-flexible rod polymer family. Although the compound itself was discovered over 150 years ago, only since the early 1980s has polyaniline captured the intense attention of the scientific community. This is due to the rediscovery of its high electrical...

(PANI), when doped with a protonic acid; and poly(dioctyl-bithiophene) (PDOT).

History

In 1862, Henry Letheby

Henry Letheby

Henry Letheby , analytical chemist and public health officer, was born at Plymouth in 1816, and studied chemistry at the Royal Cornwall Polytechnic Society. In 1837 he commenced the study of medicine, and became the assistant of Jonathan Pereira. He graduated M.B...

obtained a partly conductive material by anodic oxidation of aniline

Aniline

Aniline, phenylamine or aminobenzene is an organic compound with the formula C6H5NH2. Consisting of a phenyl group attached to an amino group, aniline is the prototypical aromatic amine. Being a precursor to many industrial chemicals, its main use is in the manufacture of precursors to polyurethane...

in sulfuric acid. The material was probably polyaniline. In the 1950s, it was discovered that polycyclic aromatic compounds formed semi-conducting charge-transfer complex salts with halogens. This finding indicated that organic compounds could carry current.
High conductivity of 1 S/cm in linear backbone polymers (in an iodine-"doped" and oxidized polypyrrole

Polypyrrole

Polypyrrole is a chemical compound formed from a number of connected pyrrole ring structures. For example a tetrapyrrole is a compound with four pyrrole rings connected. Methine-bridged cyclic tetrapyrroles are called porphyrins. Polypyrroles are conducting polymers of the rigid-rod polymer host...

black) was reported in 1963. Likewise, an actual organic-polymer electronic device was reported in the journal Science

Science (journal)

Science is the academic journal of the American Association for the Advancement of Science and is one of the world's top scientific journals....

in 1974. This device is now in the "Smithsonian Chips" collection of the American Museum of History (see figure).

However, these early discoveries were forgotten. Thus, Alan J. Heeger

Alan J. Heeger

Alan Jay Heeger is an American physicist, academic and Nobel Prize laureate in chemistry.Heeger was born in Sioux City, Iowa to a Jewish family. He earned a B.S. in physics and mathematics from the University of Nebraska-Lincoln in 1957, and a Ph.D in physics from the University of California,...

, Alan G. MacDiarmid, and Hideki Shirakawa

Hideki Shirakawa

Hideki Shirakawa is a Japanese chemist and winner of the 2000 Nobel Prize in Chemistry for his discovery of conductive polymers together with physics professor Alan J. Heeger and chemistry professor Alan G...

are often credited for the "discovery and development" of conductive polymer

Conductive polymer

Conductive polymers or, more precisely, intrinsically conducting polymers are organic polymers that conduct electricity. Such compounds may have metallic conductivity or can be semiconductors. The biggest advantage of conductive polymers is their processability, mainly by dispersion. Conductive...

s and were jointly awarded the Nobel Prize in Chemistry

Nobel Prize in Chemistry

The Nobel Prize in Chemistry is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895, awarded for outstanding contributions in chemistry, physics, literature,...

in 2000 for their 1977 report of similarly-oxidized and iodine-doped polyacetylene. Because of the numerous earlier reports of similar compounds, reviewers have questioned the Nobel citation's discovery assignment. Thus, Inzelt notes that, while the Nobelists deserve credit for publicising and popularizing the field, conductive polymers were " ..produced, studied and even applied " well before their work.

Conduction mechanisms in such materials involve resonance stabilization and delocalization of pi electrons along entire polymer backbones, as well as mobility gaps, tunneling

Tunneling

Tunneling may refer to:* Digging tunnels * Quantum tunneling, the quantum-mechanical effect where a particle crosses through a classically-forbidden potential energy barrier...

, and phonon

Phonon

In physics, a phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, such as solids and some liquids...

-assisted hopping.

Technology for plastic electronics on thin and flexible plastic substrates was developed at Cambridge University’s Cavendish Laboratory

Cavendish Laboratory

The Cavendish Laboratory is the Department of Physics at the University of Cambridge, and is part of the university's School of Physical Sciences. It was opened in 1874 as a teaching laboratory....

in the 1990s. In 2000, Plastic Logic

Plastic Logic

Plastic Logic is a spin-off company from Cambridge University's Cavendish Laboratory and specializes in polymer transistors and electronics.The firm was founded in 2000....

was spun out of Cavendish Laboratory to develop a broad range of products using the plastic electronics technology.

Features

Conductive polymers are lighter, more flexible

Flexible

Flexible may refer to:* Flexible electrical cable, also known as a power cord* Flexible electronics* Flexible response* Flexible mold* Flextime* Flexible-fuel vehicle* Flexible rake receiver* Flexible spending account, a tax-advantaged savings account...

, 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 semiconductor

Organic semiconductor

An organic semiconductor is an organic material with semiconductor properties. Single molecules, short chain and organic polymers can be semiconductive. Semiconducting small molecules include the polycyclic aromatic compounds pentacene, anthracene, and rubrene...

s, but also organic dielectrics, conductors

Electrical conductor

and light emitters.

New applications include smart windows

Smart windows

Smart glass, EGlass, or switchable glass, also called smart windows or switchable windows in its application to windows or skylights, refers to electrically switchable glass or glazing which changes light transmission properties when voltage is applied.Certain types of smart glass can allow users...

and electronic paper

Electronic paper

Electronic paper, e-paper and electronic ink are a range of display technology which are designed to mimic the appearance of ordinary ink on paper. Unlike conventional backlit flat panel displays, electronic paper displays reflect light like ordinary 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

Resistor

A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...

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.

Organic electronic devices

A 1972 paper in the journal Science proposed a model for electronic conduction in the melanin

Melanin

s. Historically, melanin is another name for the various oxidized polyacetylene

Polyacetylene

, polyaniline

Polyaniline

, and Polypyrrole

Polypyrrole

"blacks" and their mixed copolymers, all commonly-used in present day organic electronic devices. For example, 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

The University of Texas M. D. Anderson Cancer Center

The University of Texas MD Anderson Cancer Center is one of the nation's original three comprehensive cancer centers established by the National Cancer Act of 1971. It is both a degree-granting academic institution and a cancer treatment and research center located at the Texas Medical Center in...

reported an organic electronic device, a voltage-controlled switch.

Their material also incidentally demonstrated "negative differential resistance", now a hall-mark of such materials. A contemporary news article in the journal Nature

Nature (journal)

Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...

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 of the decade-earlier report of high-conductivity in a polypyrrole

Polypyrrole

, was "too early" and went unrecognized outside of pigment cell research until recently. At the time, few except cancer researchers were interested in the electronic properties of conductive polymers, in theory applicable to the treatment of melanoma

Melanoma

Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...

Plastic solar cells

Organic solar cell

An organic photovoltaic cell is a photovoltaic cell that uses organic electronics--a branch of electronics that deals with conductive organic polymers or small organic molecules for light absorption and charge transport....

s 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

Coating

Coating is a covering that is applied to the surface of an object, usually referred to as the substrate. In many cases coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wetability, corrosion resistance, wear resistance, and scratch resistance...

equipment employed to make photographic film

Photographic film

Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...

, which reduces both capital and manufacturing costs compared with conventional solar-cell manufacturing.

Silicon thin film solar cell

Thin film solar cell

A thin-film solar cell , also called a thin-film photovoltaic cell , is a solar cell that is made by depositing one or more thin layers of photovoltaic material on a substrate...

s on flexible substrates allow a significant cost reduction of large-area photovoltaics for several reasons :

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.
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

Polycarbonate

PolycarbonatePhysical PropertiesDensity 1.20–1.22 g/cm3Abbe number 34.0Refractive index 1.584–1.586FlammabilityV0-V2Limiting oxygen index25–27%Water absorption – Equilibrium0.16–0.35%Water absorption – over 24 hours0.1%...

(PC) have the potential for further cost reduction in photovoltaics. Protomorphous

Protocrystalline

A protocrystalline phase is a distinct phase occurring during crystal growth which evolves into a microcrystalline form. The term is typically associated with silicon films in optical applications such as solar cells.-Silicon solar cells:...

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.

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

ITI

Different meanings of ITI include:* Indian Telephone Industries Limited* The Institute of Translation & Interpreting, which is a professional association representing translators and interpreters in the United Kingdom....

, Pixdro, Asahi Kasei

Asahi Kasei

is a Japanese company. The main products are chemicals and materials science. The company has around 25,000 employees and had consolidated sales of ¥ 1.7 trillion in 2008. It was founded in May 1931, using the paid in capital of Nobeoka Ammonia Fiber Co., Ltd, a Nobeoka, Miyazaki based producer of...

, Merck

Merck & Co.

Merck & Co., Inc. , also known as Merck Sharp & Dohme or MSD outside the United States and Canada, is one of the largest pharmaceutical companies in the world. The Merck headquarters is located in Whitehouse Station, New Jersey, an unincorporated area in Readington Township...

, BASF

BASF

BASF SE is the largest chemical company in the world and is headquartered in Germany. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...

, HC Starck, Hitachi Chemical and Frontier Carbon Corporation among the leaders.

External links

oeindex - an index for subfields of Organic Electronics
orgworld - Organic Semiconductor World homepage

History

Features

Organic electronic devices

Plastic solar cells

See also

External links

Further reading