Plastic electronics or organic electronics is a branch of electronics that deals with device made from
organic polymer or conductive polymer. Plastics or small molecule, as opposed to Silicon.
Organic electronic because the polymers and small molecules are carbon based, like the molecules of
living things. This is as oppose to traditional electronics which relies on inorganic conductors such as silicon
Conduction mechanisms involve resonance stabilization and delocalization of pi-electrons along entire
polymers backbones as well as mobility gaps, tunneling and phonon –assisted hopping 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 application includes small windows and electronic paper. Conductive polymers are expected to
play an important role in the emerging science of molecular computing. In general, organic conductive
polymers have a higher resistance hence therefore conduct electricity poorly and inefficiently, as compared to
inorganic conductors. Researchers currently are exploring way of doping, organic semiconductors like
melanin, with relatively small amount of conductive metals to boost conductivity. However, for many
applications, inorganic conductors will remain the only viable option.
6. GENERAL OUTLOOK-
October 10, 2000
We are used to the great impact scientific discoveries have on our ways of thinking. This year's Nobel
Prize in Chemistry is no exception. What we have been taught about plastic is that it is a good
insulator - otherwise we should not use it as insulation in electric wires. But now the time has come
when we have to change our views. Plastic can indeed, under certain circumstances, be made to
behave very like a metal - a discovery for which Alan J. Heeger, Alan G. MacDiarmid and Hideki
Shirakawa are to receive the Nobel Prize in Chemistry 2000.
The men principally credited for the discovery and development of highly-conductive
polymers(at least of the rigid backbone “polyacetelene”)class are Alan J. Heeger, Alan G. macDiramid
and Hideki Shirakawa, who were jointly awarded the noble prize in chemistry in 2000 for
development of oxidized, iodine- doped polyacetelene.
We know that the electrical resistance R defined as the ratio of the voltage (V) across a conductor to
the current (I) flowing through it (i.e. R=V/I)
But, the resistance of a conductor depends upon its size and so is not a material property. It is
therefore necessary to use a parameter the resistivity which is a material property and is defined as the
resistance of a conductor of unit length with unit cross-sectional area. Resistivity has unit of ohm
meters (Ωm) in the S.I. system. To compare the properties of conductors it is more convenient to use
conductivity S which is simply the reciprocal of the resistivity i.e.
This is preferred because S is higher for better conductors its S.I. units are reciprocal
ohm meters or siemens per meter (S/M).
Electrically conductive polymers are mainly derivative of poly acetylene black (the simplest melanin)
7. Examples include:
PA (more specifically iodine doped Tran’s polyacetylene)
Polyaniline: PANI, when doped with a protonic acid,
Poly (dioctylbi thiophene): PDOT
CHEMICAL BONDING AND CONDUCTIVITY-
The higher no. of free electrons in metals such as copper and iron leafs to higher levels of
conductivity compared with covalently-bonded insulators such as Diamonds where there are none.
The effect of chemical bonding upon conductivity can be seen in fig.1
It is produced in two isomeric forms, cis and Trans polyacetelenes. The particular isomer
obtained depends upon the temperatures at which the polymerization was performed. Reactions at
78۠0C produce mainly the cis-confirmation where as none of the trans-form is also be converted to the
thermodynamically more stable trans-form by heating typically at 170۠0C for 20 minutes.
The properties of the polymer are also affected by this isomerisation. Films of the cis material
are red in transmitted light and the smooth surface has a coppery appearance where as the trans
material is blue in transmission and silvery in reflection. More important the conductivity of the
polymer increase with the cis to Tran’s isomerisation from about 10 -9 S/cm to up to 10-4 S/cm. Hence
pure PA is never more than a semiconductor this is because unlike other unsaturated molecules.
In spite of the lack of intrinsic conductivity in PA the conductivity is greatly increased to
metallic levels by “doping” with certain types of molecules and ions.
Substantial increases are obtained using either electron accepting molecules (oxidizing agent)
such as iodine, bromine and arsenic penta fluoride or electrons doners (reducing agent) such as alkali
metals. It is pointed out however that the term doping in thix context refers to the inclusion of
substantial quantities of dopant in the polymer. This is to be contrasted with convential
semiconductors technology where dopant concentrate are measure in ppm.
9. There is a rapid rise more slowly with further addition of dopant. The measured conductivity
for PA treated with different dopant are listed in table-1 with the highest value(S) 1000(S/cm) being
obtained for strong electrons acceptors such as AsF and oriented PA films.
It is possible to tailor the level of conductivity and types of carriers by treating with donor-
doped (n-type) or acceptors doped (p-type) PA.
WHAT EXACTLY HAPPENED IN THE POLYACETYLENE
When we compare some common compounds with regard to conductivity, we see that the
conductivities of the polymers vary considerably. Doped polyacetylene is, e.g., comparable to good
conductors such as copper and silver, whereas in its original form it is a semiconductor.
Polypyrrole (ppy) is made by electron polymerization of pyrrole. Blue black, acceptors doped
conducting polymers is produced at the anode when the monomer solution is electrolyst in the
presence of Et4N+BF4. The films have the conductivity of the order of 100 S/cm and for stabilities.
The films are essentially amorphous and it is readily shown by chemical analysis that they are not pure
polymer but contain one BF4 ion for every four pyrrole rings.
10. HOW CAN PLASTIC BECOME CONDUCTIVE?
Plastics are polymers, molecules that form long chains, repeating themselves like pearls in a
necklace. In becoming electrically conductive, a polymer has to imitate a metal, that is, its electrons
need to be free to move and not bound to the atoms. The first condition for this is that the polymer
consists of alternating single and double bonds, called conjugated double bonds. Polyacetylene,
prepared through polymerization of the hydrocarbon acetylene, has such a structure:
However, it is not enough to have conjugated double bonds. To become electrically
conductive, the plastic has to be disturbed - either by removing electrons from (oxidation), or inserting
them into (reduction), the material. The process is known as doping.
11. The game in the illustration to the right offers a simple model of a doped polymer. The pieces
cannot move unless there is at least one empty "hole". In the polymer each piece is an electron that
jumps to a hole vacated by another one. This creates a movement along the molecule - an electric
current. This model is greatly over-simplified, and we shall consider a more "chemical" model later.
Heeger, MacDiarmid and Shirakawa found was that a thin film of polyacetylene could be
oxidised with iodine vapour, increasing its electrical conductivity a billion times. This sensational
finding was the result of their impressive work, but also of coincidences and accidental circumstances.
Let us, shortly, tell the story of one of the great chemical discoveries of our time.
MANUFACTURING PLASTIC ELECTRONICS-
The heart of modern electronics are micro chips circuits and wiring diagrams are designed and
micro miniaturized to the point that thousands or even millions of circuits are contained in a one inch
square chip which is burned on to ultra thin inorganic materials life refined silicon using very high
12. Plastic electronics, on the other hand, follow a different manufacturing process. The process
starts with the manufacturing of large sheets of PET plastics. The flexible but tough material used in
the production of plastic bottles. Circuits are then printed on these sheets using ink-jet printers or using
techniques much like those used to print magazines and news papers- resulting in a process that is
cheap, easy to do and faster to produce.
The plastic circuit will be used as the active matrix back panes for large but flexible electronic
displays. In an active matrix display, every dot on displays managed by a switching element such as
thin film transistors (TFTs) and the signals on the array of intersecting row and column electrodes.
Prior to plastic electronics, these TFTs have been produced using amorphous silicon deposited on a
rigid glass substrate at high temperature through a complex series of production procedures.
It is the collection of switching elements and row-column electrodes which are put together on
a substrate to for the active matrix back pane, which is then combined with different front plate
technologies (LCD screens) to form display.
For many electronic readers the best front plane technology e-paper which looks like paper and
only uses unit’s power when the image shifts or changes.
E-paper however loses its thinness and flexibility when combine with a glass based silicon
back pane. The flexible back pane technology of plastic electronic allows the reader device to become
flexible, light thin and robust enough for a wide range of uses no paper has gone before and to include
large data storage capacities.
14. INORGANIC Vs ORGANIC-
Organic electronic or plastic electronic is the branch of electronic that deals with conductive
polymers which are carbon based.
Inorganic electronic, on the other hand, relies on inorganic conductors like copper and silicon.
• Organic electronics are lighter, more flexible and less expensive than there inorganic
• They are also biodegradable (being made from carbon e.g. melanin).
• This opens the doors to many exciting and advanced new applications that would be
impossible using copper or silicon.
• However conductive polymers have high resistance and therefore are not good conductor of
• In many cases they also have shorter life time.
• Much more dependent on stable environment conditions than inorganic electronics would be.
Low capital $1-$10 billion
Flexible plastic substrate rigid glass or metal
Ambient processing Ultra clean room
Continuous direct printing Multistep photolithography
15. Conjugated Polymers: Electronic Conductors
The most important aspect of conjugated polymers from an electrochemical perspective is their
ability to act as electronic conductors. Not surprisingly -electron polymers have been the focus of
extensive research, ranging from applications of ``conventional'' polymers (e.g., polythiophene,
polyaniline, polypyrrole) in charge storage devices such as batteries and super capacitors, to new
polymers with specialized conductivity properties such as low band gap and intrinsically conducting
polymers. Indeed, many successful commercial applications of these polymers have been available for
more than fifteen years, including electrolytic capacitors, "coin'' batteries, magnetic storage media,
electrostatic loudspeakers, and anti-static bags. It has been estimated that the annual global sales of
conducting polymers in the year 2000 will surpass one billion US dollars. Clearly these materials have
considerable commercial potential both from the continued development of well established
technologies and from the generation of new concepts such as those to be presented in this thesis.
Shirakawa can trace the genesis of the field back to the mid 1970s when the first polymer
capable of conducting electricity polyacetylene was reportedly prepared by accident. The subsequent
discovery by Heeger and MacDiarmid that the polymer would undergo an increase in conductivity of
12 orders of magnitude by oxidative doping quickly reverberated around the polymer and
electrochemistry communities, and an intensive search for other conducting polymers soon followed.
The target was (and continues to be) a material, which could combine the processibility,
environmental stability, and weight advantages of a fully organic polymer with the useful electrical
properties of a metal.
The essential structural characteristic of all conjugated polymers is their quasi-infinite
system extending over a large number of recurring monomer units. This feature results in materials
with directional conductivity, strongest along the axis of the chain. The simplest possible form is of
course the archetype polyacetylene (CH) x shown in Figure While polyacetylene itself is too unstable
to be of any practical value, its structure constitutes the core of all conjugated polymers. Owing to its
structural and electronic simplicity, polyacetylene is well suited to ab initio and semi-empirical
calculations and has therefore played a critical role in the elucidation of the theoretical aspects of
Figure 1.2: Conjugated polymer structure: (a) trans- and (b) cis-polyacetylene, and (c) polythiophene
Electronically conducting polymers are extensively conjugated molecules, and it is believed
that they possess a spatially delocalized band-like electronic structure. These bands stem from the
splitting of interacting molecular orbital of the constituent monomer units in a manner reminiscent of
the band structure of solid-state semiconductors.
17. Figure 1.3: Band structure in an electronically conducting polymer
It is generally agreed that the mechanism of conductivity in these polymers is based on the
motion of charged defects within the conjugated framework. The charge carriers, either positive p-type
or negative n-type, are the products of oxidizing or reducing the polymer respectively. The following
overview describes these processes in the context of p-type carriers although the concepts are equally
applicable to n-type carriers.
Figure 1.4: Positively charged defects on poly (p-phenylene). A: polaron B: bipolaron
Oxidation of the polymer initially generates a radical cation with both spin and charge.
Borrowing from solid state physics terminology, this species is referred to as a polaron and comprises
both the hole site and the structural distortion which accompanies it. This condition is depicted in
Figure 1.4A. The cation and radical form a bound species, since any increase in the distance between
them would necessitate the creation of additional higher energy quinoid units. Theoretical treatments
have demonstrated that two nearby polarons combine to form the lower energy bipolaron shown in
Figure 1.4 B. One bipolaron is more stable than two polarons despite the coulombic repulsion of the
18. two ions. Since the defect is simply a boundary between two moieties of equal energy -- the infinite
conjugation chain on either side -- it can migrate in either direction without affecting the energy of the
backbone, provided that there is no significant energy barrier to the process. It is this charge carrier
mobility that leads to the high conductivity of these polymers.
The conductivity of a conducting polymer is related to the number of charge carriers n and
their mobility :
σ α µn
Because the band gap of conjugated polymers is usually fairly large, n is very small under
ambient conditions. Consequently, conjugated polymers are insulators in their neutral state and no
intrinsically conducting organic polymer is known at this time. A polymer can be made conductive by
oxidation (p-doping) and/or, less frequently, reduction (n-doping) of the polymer either by chemical or
electrochemical means, generating the mobile charge carriers described earlier. The cyclic
voltammetry of electronically conducting polymers is characterized by broad non-Nernstian waves. A
typical example is shown in Figure for an N-substituted pyrrole based conducting polymer.
Figure 1.5: Cyclic voltammogram of a substituted polypyrrole.
19. SPECIFYING PLASTICS FOR ELECTRONICS DESIGN
Although not always an easy task, selecting the right plastics can help ensure the safety and
reliability of today's electronics.
Most electronic equipment uses some type of thermoplastic. It is important to understand the
characteristics of plastics used in electronics equipment to determine which plastic is appropriate for a
given application. These characteristics often affect the safety and reliability of the final product. This
article examines many factors surrounding plastics selection that engineers should consider during a
product's design stages.
Underwriters Laboratories (UL) has one of the most comprehensive materials databases
available, and UL 94 ratings are widely accepted flammability performance standards for plastic
materials. The UL 94 standard explains various flammability categories and describes the test methods
used for each rating.
Each material tested can receive several ratings based on color and thickness. The amount and
type of color additive can vary the flammability rating of a plastic. The UL plastic component
directory normally specifies four colors: black, white, red, and natural. When specifying a material for
an application, the UL rating should be applicable for the thickness used in the wall section of the
plastic part. It is very important to remember that the thickness must always be reported with the UL
rating to provide meaningful information about the material's characteristics. Ratings are categorized
Ratings are differentiated primarily by the testing method. The classification depends on the following
• Sample orientation (horizontal or vertical).
• Burn rate.
• Time to extinguish.
• Resistance to dripping.
20. • Drip flammability.
These parameters affect the end results, and hence the classification. With this in mind, each
material tested could receive several ratings, depending on its color and thickness. Some ratings apply
to specific product types. VTM, for example, refers to very thin material. HBF, HF-1, and HF-2 refer
to foamed materials. These ratings, therefore, should not be compared to those in other categories. In
other words, a vertically rated plastic material is better than a plastic that simply meets the HB
requirements. In addition, a material accepted for a 5V rating must first comply with the vertical test
requirements for V-0, V-1, or V-2. Depending on the end-product application, a designer could specify
one or more ratings for a product.
Some engineers make the erroneous assumption that there is a direct correlation between a
material's UL rating and its operating temperature. UL ratings relate only to a material's behavior when
introduced to a flame source. How a material reacts when the flames come in direct contact with it
determines its UL rating. For example, for a rating of 94V-0, a material must be self-extinguishing and
must not drip or run while burning.
In the test, a sample of the material is held over a Bunsen burner, ignited, and allowed to burn.
When the sample is removed from the flame, the fire must go out within 10 seconds, and the material
must not have dripped from the burning sample. If the material continues to burn or if it drips and
runs, it cannot be rated 94V-0. For this rating, operating temperature never comes into play.
Component Flammability Requirements
Enclosure 94V-1 or better
Printed circuit board 94V-1 or better
Integrated circuit, 94HB or better
package, capacitor, and
21. other small parts
Cord anchorage bushing 94HB or better
Operating temperature is determined by establishing the point at which temperature causes an
end product to cease to perform as it was intended. This premise applies to minimum as well as
maximum temperatures. Most nylon materials, for example, have a maximum operating temperature
of 250°F (120°C). However, the actual operating temperatures of finished goods vary depending on
the mass (volume of material), temperature variations over time, and mold factor. A 94V-0 rating for a
material does not necessarily mean that a finished product can withstand a high temperature.
SAFETY STANDARDS AND PLASTICS
Almost all product safety standards have clauses concerning flammability requirements for
plastics in electronics. Requirements normally cover plastics that support live parts, such as a
transformer's bobbin; enclosure of live parts, such as a monitor cover; and decorative parts, such as a
lamp cover. EN 60950, for example, has guidelines specifying minimum requirements for plastic
Most electrical and electronic equipment has some type of enclosure. Enclosures are normally
evaluated to meet one or more of the following requirements:
• A fire enclosure must prevent the spread of fire and flames.
• An electrical enclosure must prevent access to hazardous voltages or parts that carry hazardous
• A mechanical enclosure must prevent injury from physical or mechanical hazards.
A product can have one or more enclosure types. Section 4 of EN 60950 requires that fire and
electrical enclosures meet certain parameters in order to be considered effective. A summary of these
requirements is presented here, but it is essential that designers refer to the standard for complete
22. The top and side openings of the enclosure must satisfy one of the following conditions: do not
exceed 5 mm in any dimension; do not exceed 1 mm in width regardless of length; are constructed
with louvers shaped so that they deflect external, vertically falling objects outward; are located so that
objects, upon entering the enclosure, are unlikely to fall on bare parts at hazardous voltages.
If the end product is a stationary or movable equipment with a mass of 18 kg or greater, fire
enclosures are considered to comply without test if, in the smallest thickness used, the material is of
flammability class 5V.
The bottom of a fire enclosure—or individual barriers—must provide protection underneath all
internal parts, including partially enclosed components or assemblies that could emit, under fault
conditions, material likely to ignite the supporting surface.
If a hole is cut to fit a plastic window or a screen in a fire enclosure, then the window or screen
must have a flammability rating of 5V. However, if a hole is cut to accommodate a fuse holder, a
switch, or similar components, then there is no need for these components to meet 5V flammability
requirements, provided that such components have appropriate approvals.
One source of valuable information is the UL Recognized Component Directory, also known
as the UL Yellow Book. This directory provides names of companies authorized by UL to provide
plastic components bearing a UL mark. It also provides technical information about various plastics.
The book uses some important abbreviations and terms (see sidebar below).
The UL Directory: Key Terms and Abbreviations
23. ALL: All Color.
Any possible color has been recognized.
This indicates the specific color of the plastic material onto which the recognition (UL mark) is
CTI: Comparative Tracking Index.
CTI is expressed as the voltage that causes tracking after 50 drops of 0.1% ammonium chloride
solution have fallen on the material. The results of testing the nominal 3-mm thickness are considered
representative of the material's performance in any thickness.
D-495: Arc Resistance.
Measured in accordance with ASTM D-495, arc resistance is expressed as the number of seconds that
a material resists the formation of a surface conducting path when subjected to an intermittently
occurring arc of high-voltage, low-current characteristics. The results of testing the nominal 3-mm
thickness are considered representative of the material's performance in any thickness.
HAI: High Amp Arc Ignition.
Ignition performance is expressed as the number of arc rupture exposures (standardized as to
electrode type and shape, and electric circuit) necessary to ignite a material when applied at a standard
rate on the materials surface.
HVTR: High Voltage Arc Tracking Rate.
Measured in mm/min, HVTR is denoted as the rate that a tracking path can be produced on the
surface of the material under standardized test conditions. A note is made if the material ignites. The
24. results of testing the nominal 3-mm thickness are considered representative of the material's
performance in any thickness.
HWI: Hot Wire Ignition.
Ignition performance is also expressed as the mean number of seconds needed to either ignite
standard specimens or to burn through specimens without ignition. Specimens are wrapped with
resistance wire that dissipates a specified level of electrical energy to determine the ignition rate.
Min Thk mm: Minimum Thickness (mm).
This represents the thickness of the specimen subjected to tests. This designation is important because
a number of properties are strictly dependent on the specimen thickness.
NC: Natural Color.
NC indicates that only the unpigmented material is covered by the recognition.
RTI: Relative Temperature Index.
RTI is an investigation of a material with respect to its retention of certain critical properties (e.g.,
dielectric, tensile, impact) as part of a long-term thermal-aging program, conducted according to UL
746B. The temperature index indicates the temperature (°C) above which the material is likely to
degrade prematurely. The printed value refers to the extrapolation to approximately 100,000 hours
with the retention of at least 50% of its original value after the aging test. Depending on the property
requirements for a given application, three different RTI expressions are possible: electrical (Elec),
mechanical with impact (Mech with imp), or mechanical without impact (Mech w/o imp).
UL 94: Flame Class.
This classification of the material is based on burning tests conducted in accordance with UL 94 (a
gas-burner test on a small-scale specimen).
Selecting the appropriate plastic material for a particular design is often the most difficult task
a designer must face. Many factors-
1. Such as ability to mold or machine, weight, cost, thermal behavior,
2. Flammability rating- affects the final decision.
Because no plastic is likely to meet all of a designer's requirements for a particular application,
some degree of compromise is almost always necessary in designing plastic parts for electronics.
Selecting a material cannot be based simply on a comparison of numbers from published data
sheets. Values from data sheets often represent laboratory tests that may not duplicate real-life
molding conditions. For example, it is a mistake to choose the most economical material for a part by
comparing the cost per pound of various plastics. Some plastics weigh twice as much per cubic inch as
others, and so it would then require twice as much material to fill a given cavity-and cost twice as
much to ship.
The choice of any material should be based on the best combination of required properties. An
ideal material will have a value for each required property just sufficient to perform properly and
safely in a given application. A molded plastic part is significantly affected by processing factors such
as direction of flow, pressure during molding, melting temperature, thermal degradation, cooling rate,
and stress concentrations. A high value provided in a data sheet could be reduced considerably by
There is no simple procedure for selecting the best plastic for a new application. Understanding
the behavior of a plastic under real-life conditions is critical to determining how the material will
perform after it is molded. Successfully designing plastic parts that demonstrate optimal cost and
performance characteristics requires learning as much as possible about many different plastics, and
understanding the peculiarities of their processing.
26. One of the first design considerations to establish is whether thermosetting materials or
thermoplastics are appropriate. Thermosetting materials are initially soft but change irreversibly hard
upon heating. Thermoplastics can be repeatedly softened by heating and hardened again by cooling.
Designers must study the generic properties of different compounds to become familiar with their
To make this determination, it is often helpful to consult molders and plastics manufacturers.
However, such advice should be taken cautiously because these sources do not have access to internal
factors such as production, engineering, purchasing, and marketing considerations. Molders can often
detect and correct visible problems or readily measured factors such as color, surface condition, and
dimensions. However, without extensive testing and quality control, less-apparent property changes
may not show up until the molded parts are in service. Properties such as impact strength, toughness,
and chemical resistance can be diminished by improper control of processing parameters. Molding
processes can alter the published data-sheet properties, reducing strength as well as creating areas of
HOW POLYMER CONDUCTIVITY WAS REAVEALED?
The leading actor in this story is the hydrocarbon polyacetylene, a flat molecule with an angle
of 120° between the bonds and hence existing in two different forms, the isomers cis-polyacetylene
and trans-polyacetylene. At the beginning of the 1970s, the Japanese chemist Shirakawa found that it
was possible to synthetisize polyacetylene in a new way, in which he could control the proportions of
cis- and trans-isomers in the black polyacetylene film that appeared on the inside of the reaction
vessel. Once - by mistake - a thousand-fold too much catalyst was added. To Shirakawa's surprise, this
time a beautiful silvery film appeared.
Shirakawa was stimulated by this discovery. The silvery film was trans-polyacetylene, and the
corresponding reaction at another temperature gave a copper-coloured film instead. The latter film
appeared to consist of almost pure cis-polyacetylene. This way of varying temperature and
concentration of catalyst was to become decisive for the development ahead.
In another part of the world, chemist MacDiarmid and physicist Heeger were experimenting with a
27. metallic-looking film of the inorganic polymer sulphur nitride, (SN)x. MacDiarmid referred to this at a
seminar in Tokyo. Here the story could have come to a sudden end, had not Shirakawa and
MacDiarmid happened to meet, accidentally, during a coffee-break.
When MacDiarmid heard about Shirakawa's discovery of an organic polymer that also gleamed like
silver, he invited Shirakawa to the University of Pennsylvania in Philadelphia. They set about
modifying polyacetylene by oxidation with iodine vapour. Shirakawa knew that the optical properties
changed in the oxidation process and MacDiarmid suggested that they ask Heeger to have a look at the
films. One of Heeger's students measured the conductivity of the iodine-doped trans-polyacetylene and
- eureka! The conductivity had increased ten million times!
In the summer of 1977, Heeger, MacDiarmid, Shirakawa, and co-workers, published their discovery in
the article "Synthesis of electrically conducting organic polymers: Halogen derivatives of
polyacetylene (CH)n" in The Journal of Chemical Society, Chemical Communications. The discovery
was considered a major breakthrough. Since then the field has grown immensely, and also given rise
to many new and exciting applications. We shall return to some of them.
DOPING- FOR BETTER MOLECULE PERFORMANCE
A metal wire conducts electric current because the electrons in the metal are free to move.
28. The higher no. of free electrons in metals such as copper and iron leafs to higher levels of
conductivity compared with covalently-bonded insulators such as Diamonds where there are none.
When describing polymer molecules we distinguish between (sigma) bonds and (pi) bonds. The
bonds are fixed and immobile. They form the covalent bonds between the carbon atoms. The
electrons in a conjugated double bond system are also relatively localised, though not as strongly
bound as the electrons. Before a current can flow along the molecule one or more electrons have to
be removed or inserted. If an electrical field is then applied, the electrons constituting the bonds can
move rapidly along the molecule chain. The conductivity of the plastic material, which consists of
many polymer chains, will be limited by the fact that the electrons have to "jump" from one molecule
to the next. Hence, the chains have to be well packed in ordered rows.
As mentioned earlier, there are two types of doping, oxidation or reduction. In the case of
polyacetylene the reactions are written like this:
Oxidation with halogen (p-doping): [CH]n + 3x/2 I2 --> [CH]nx+ + x I3-
Reduction with alkali metal (n-doping): [CH]n + x Na --> [CH]nx- + x Na+
The doped polymer is a salt. However, it is not the iodide or sodium ions that move to create the
current, but the electrons from the conjugated double bonds. Furthermore, if a strong enough electrical
field is applied, the iodide and sodium ions can move either towards or away from the polymer. This
means that the direction of the doping reaction can be controlled and the conductive polymer can
easily be switched on or off.
POLARONS- DOPED CARBON CHAINS
In the first of the above reactions, oxidation, the iodine molecule attracts an electron from the
polyacetylene chain and becomes I3- . The polyacetylene molecule, now positively charged, is termed a
radical cation, or polaron (fig. b below).
29. The lonely electron of the double bond, from which an electron was removed, can move easily. As a
consequence, the double bond successively moves along the molecule. The positive charge, on the
other hand, is fixed by electrostatic attraction to the iodide ion, which does not move so readily. If the
polyacetylene chain is heavily oxidised, polarons condense pair-wise into so-called solitons. These
solitons are then responsible, in complicated ways, for the transport of charges along the polymer
chains, as well as from chain to chain on a macroscopic scale.
We have only touched upon the complex theory that explains how polymers can be made electrically
30. APPLICATION OF PLASTIC ELECTRONICS-
ORGANIC LIGHT EMITTING DIODES (OLEDs)-
• An electron and hole pair is generated inside the emissive layer.
• When the electron and hole combine, a photon is produced, this will show up as a dot of light
on the screen.
• Many OLEDs together on a screen make up a picture.
WHAT IS OLED-
An OLED or Organic Light-Emitting Diode is a light emitting device based on the principle of
electrophosphorescence. Several types of organic material that will glow red, green and blue are
placed between two layers of conductive material and covered with glass or another translucent
protective material. When electric current is applied, the conductive layers act as anode (positively
charged) and cathode (negatively charged), enabling the flow of energy from the negative layer to the
31. positive layer and stimulating the organic material to emit a bright light. The two most common types
The two most common types of OLED:
SMOLED or Small Molecular OLED:
Layers of organic material with very small molecular structures are assembled using vacuum vapor
Poly-OLED or Polymer OLED:
Layers are prepared by spin coating a surface with large molecular structure organic polymers
For the deposition of organic thin film, our group investiagates evaporation techniques such as Vapour
Thermal Evaporation (VTE) and Organic Vapur Phase Deposition (OVPD). In combination with our
experimental lineup, comprising x-ray-diffraction and -reflectometry, atomic-force microscopy,
ellipsometry and electrical characterization methods, we are able to produce multi-layer samples (e.g.
OTFTs as shown in fig. 3) and characterize them with respect to their optical, structural,
morphological and electrical properties.
32. OLED vs. LCD
A non-organic LCD display does not emit light; a backlight sits behind the LCD panel and to create
the image you see on screen, individual liquid crystals allow light to pass or block it. OLED computer
displays do not require a backlight since the organic material self-generates light, so they require very
little external power.
1. Active OLED
2. Passive OLED
FIGURE OF PASSIVE OLED
33. ORGANIC THIN FILM
Fig. 1: Surface of an organic thin film detected with an AFM (Atomic Force Microscope).
Thin organic films (10-1000nm), that serve as active layers in both electrical (e.g. transistors) and
optical (e.g. light emitting diodes) devices.
In the field of organic transistors (OTFT – Organic Thin-Film Transistors), especially crystalline
materials such as Pentacene and Perylene are of importance. They grow as polycrystalline islands (fig.
1). Such transistors can be employed as control elements for organic displays. The important
advantages of organic over inorganic transistors (e.g. based on silicon or germanium) are the ability of
low-cost production and the prospect of using flexible substrates. This facilitates the development of
In contrast to the crystalline materials employed for OTFTs, amorphous organic films are used for
organic light emitting diodes (OLEDs). Already today, OLEDs can be found in many products such as
cell phones and digital cameras due to the high level of efficiency and the brilliant colors. Moreover,
organic displays do not exhibt color shifting upon variation of the angel of vision. In addition to
displays also their use as illuminants is of interest (fig. 2). Some of our investigated materials, e.g.
ALq3 and alpha-NPD, are suitable candidates for these applications.
34. ORGANIC THIN FILM TRANSISTORS (OTFTs)
Organic transistors are transistors that use organic molecules rather than silicon for their active
DIFFRENCE BETWEEN TFT AND OTFT-
1. Silicon deposited on glass.
2. The deposited silicon must be crystallized using laser pulses at high temperatures.
Active layers can be thermally evaporated and deposited on any organic substrate a flexible
piece of plastic at much lower temperatures.
ADVANTAGE OF ORGANIC TRANSISTORS
– Compatibility with plastic substances
– Lower temperature is used while manufacturing (60-120°C)
– Lower cost and deposition processes such as spin-coating, printing and evaporation
DISADVANTAGE OF ORGANIC TRANSISTORS
– Lower mobility and switching speeds compared to Si wafers
– Usually does not operate under invasion mode.
35. CHALLENGES INVOLVED
– Workarounds for complications with photo resists.
– To find organic semiconductors with high enough mobility and switching times.
FEATURES OF OTFTs-
• Mobility greater than 0.1 cm2/Vs
• On/off ratio greater than 106
ORGANIC NANO RADIO FREQUENCY IDENTIFICATION
• Quicker Checkout
• Inventory Control
• Reduced Waste
• Efficient flow of goods from
PRODUCTION SPECIFICATIONS OF MANUFACTURING A
• > 96 bits
• Four main communication Bands: 135 KHz, 13.56 MHz, 900 MHz, 2.4 GHz
• Vacuum Sublimation
•Integrates electronic devices into textiles, like clothing
•Made possible because of low fabrication temperatures
•Has many potential uses, including: Monitoring heart-rate and other vital sign controlling embedded
devices (mp3 players), keep the time…
36. LAB ON CHIP
•A device that incorporates multiple laboratory functions in a single chip
•Organic is replacing some Si fabrication methods:
1. Lower cost
2. Easier to manufacture
3. More flexible Portable, Compact Screens
•Screens that can roll up into small devices
Metal wires that conduct electricity can be made to light up when a strong enough current is
passing - as we are reminded of every time we switch on a light bulb. Polymers can also be made to
light up, but by another principle, namely electroluminescence, which is used in photodiodes. These
photodiodes are, in principal, more energy saving and generate less heat than light bulbs.
In electroluminescence, light is emitted from a thin layer of the polymer when excited by an electrical
field. In photodiodes inorganic semiconductors such as gallium phosphide are traditionally used, but
now one can also use semiconductive polymers.
Electroluminescence from semiconductive polymers has been known for about ten years. Today there
is extensive commercial interest in photodiodes and in light-emitting diodes (LEDs). A LED can
consist of a conductive polymer as an electrode on one side, then a semiconductive polymer in the
middle and, at the other end, a thin metal foil as electrode. When a voltage is applied between the
electrodes, the semiconductive polymer will start emitting light.
37. High resolution
There are many applications of this brilliant plastic. In a few years, for example, flat television
screens based on LED film will become reality, as will luminous traffic signs and information signs.
Since it is relatively simple to produce large, thin layers of plastic, one can also imagine light-emitting
wallpaper in our homes, and other spectacular things.
Some applications of conductive polymers that have come onto the market, or are undergoing trials,
• Polythiophene derivates, those are of great commercial use in antistatic treatment of
photographic film. They can also be used in devices in supermarkets for marking products. The
checkouts will then automatically register what the customer has in the trolley.
• Doped polyaniline in antistatic material, e.g. in plastic carpets for offices and operating
theatres, where it is important to avoid static electricity. It is also used on computer screens,
protecting the user from electromagnetic radiation, and as a corrosion inhibitor.
• Materials such as polyphenylenevinylene may soon be used in mobile phone displays.
• Polydialkylfluorenes are used in the development of new colour screens for video and TV.
38. OTHERS APPLICATIONS
The Powerstrip that could save your life
Wednesday, December 19th, 2007
Every now and then an invention comes along that looks or sounds silly. The Smoke Shutoff power
strip, from Exact Products, is the exact opposite. Ingenuity at its best, this product is one of those
things you wish you thought of. It’s a power strip which shuts off electricity to attached devices when
smoke is detected. On top of that, an alarm sounds until the smoke hazard is gone. And on top of that,
the strip won’t restore power until you hit a reset button! That’s 3 levels of safety craziness!!! This
product could be used anywhere, but I really see it working well in businesses that use a lot of
machines. The Smoke Shutoff has completed testing and now just needs a distributor, so someone
contact Exact Products and get going!
39. Batteries of the Future!!!
Monday, March 26th, 2007
They say that plastic is good for us. Three scientists in Japan decided that it was great for us. They
created an organic polymer film that can be used as a rechargeable battery. They claim it could retain
a charge over longer periods of time and have a life lasting over 1,000 recharging. The craziest thing
is that it can recharge fully in only one minute. This would definitely be useful in any of the
emergency fields in all sorts of electronics and emergency response gear, but it seems like they could
easily get lost. My slogan pitch- ‘This radio is charged by the minute-man.’ Careful, it might develop
Wireless Digital Pen and Mouse
Sunday, March 4th, 2007
EPOS had the right idea with the new digital pen they came out with. Users can capture and display
handwritten notes on a computer, use it as a mouse, and or draw those fun Waldo pictures we all love,
all without the need for paper or tablets. The best part is that the pen is wireless, so you don’t have to
worry about it getting in the way, but you do have to worry about losing it in between the seat of your
car. For all those agencies stuck in the Stone Age, this would be great for digitizing your reports, and
for everyone else in the technological ‘know’, this would be useful in a plethora of situations.
40. Digital Cameras with printers
Monday, February 5th, 2007
A new company called Zink, with Polaroids help, is working on a digital Polaroid camera. The sweet
camera will have a built in printer. Zink is developing the miniaturized printers that will be small
enough to fit into the cameras. Instead of using ink the company is testing paper that is capable of
turning any color and the printer would just tell every ‘pixel’ what color to turn. Sounds cool and
creepy at the same time. Either way this would be awesome out in the field for photo support for
accidents, parking disputes, or anything else. Now you won’t be able to blame the camera on deleting
your photos. -
41. Self-Energizing Medical Gadgets
Thursday, December 21st, 2006
Energy is something that all medical gadgets and products need to run. Pacemakers and the like all
use some type of power to function. A consortium in the UK consisting of Zarlink Semiconductor,
InVivo Technology, Finsbury Orthopedics and others are being commissioned by the UK Department
of Trade and Industry to create a power source for any and all medgadgets by using our own kinetic
energy. This prototype that is pictured works by the motion of a moving coil through a static magnetic
field to induce a voltage across the coil, which creates the energy. This could definitely help in not
just the medical fields, but in any emergency related fields.
42. Release the Wild Charger in you!!
Thursday, December 14th, 2006
We are still a few years off from complete wireless charging of every device in the world, but for now
Wild charger has the idea. The Wild charger charges your electronic devices through the metal
contacts on your devices. The only cord in the whole ordeal is the AC Cord for the charger. This
thing could definitely tidy up the work area of cords as well as charge all 5 billion of your devices.
They hope to release it early next year with a price tag between $40 and $100. I’m guessing it will go
for the latter amount. This kind of technology would be great for charging cell phones, radios, AED’s,
43. Mini Display for Designer Glasses
Wednesday, December 13th, 2006
Lumus-Optical out of Isreal decided that the horrible LCD Goggles that are out on the market aren’t
fashionable enough. They say they have a working prototype of LCD Glasses. The glasses come with
two micro displays that are capable of displaying a projected image of 60 inches from 10 feet. The
best part is that they use Light-guide Optical Element that displays this image on your regular lenses
so you can still see through the glasses. This would make watching a movie way easier while driving.
The image quality boasts a 640×480 resolution and will even come with a tiny projector on the arm.
This would be awesome for Police Officers out in the field. They would be able to watch movies
during down timer see the returns of pictures of bad guys from dispatch. There could be a multitude
of ways to use this in the Emergency field.
44. Gamma Radiation Watch
Saturday, December 9th, 2006
No, this doesn’t shoot lasers at bad guys. The Gamma Watch from Environmental Instruments
Canada Inc. actually detects radiation. It displays dose rate as well as cumulative dose. You do need
to make sure you set the radiation level that you want the alarm to go off before you deteriorate. This
thing is so popular (in the UK I’m guessing) that it is actually sold out and a newer model is being
made. It will go for $250 and will be especially helpful when you’re diving up to 50 meters. By
Acoustic Sensitive to the touch
Thursday, November 30th, 2006
Researchers in Europe have come up with Tai-Chi or the Tangible Acoustic Interfaces for Computer-
Human Interaction that is a series of acoustic sensors that turn any surface into a touch-sensitive
computer interface. The system uses sonar tracking that senses surface vibrations and can track up to
two things at once. This could be very useful in the work place like hospitals who are concerned about
hygiene, because the clean up is non-existent. This could also clear the bulk of wires and hardware
used in the Police and Fire fields when typing up reports or using your Mobile Date Computer to
respond to calls. There is no release date for any products yet, but I’m sure once its perfected there
will be a product. Soon, we could all have the holographic touch screens just like in the futuristic
45. Gamma-Scout- Life Saving Tool
Thursday, November 30th, 2006
Eurami got it right when they created the Gamma-Scout Radiation detector. The control panel lets you
display alpha, beta, gamma, and x-rays in pulse or rate mode on the LCD. You can punch in time,
date, and logging intervals; and check the battery level. The set-and-forget device sounds an alert
when radiation exceeds a specified limit, and bundled software lets you shoot data to your PC for
analysis via USB 2.0. The unit is packaged in high impact Novodur molding so you can bang it all
over the place without ruining it and the V-Max battery, also included, is good for a decade of always-
on monitoring. That’s a damn good long time for measuring radiation during the nuclear holocaust
years to come. All this at only 6oz., I would have to say for any Police/Fire/Medical agency needing a
gieger counter to go out and spend the $399, which isn’t a bad price for the use and longevity.
46. Snapalarm: Like legos
Wednesday, November 29th, 2006
Everyone has had to replace their smoke detector batteries a billion times in their homes. You have to
get a chair and try and pry the whole thing off the ceiling to shut it up. Now with the Snapalarm
smoke detector it makes it much easier to simplify these menial tasks. The Snapalarm is a clam shell
design that will snap onto any wire, chain, or wire/chain size cord. The best part is that it won’t lock
close unless it has a working battery. It sells for $50, which is not too bad for the stylish bulb that may
just save your life some day.
COPS all the time
Wednesday, November 22nd, 2006
It was only a matter of time, but British Police in London will now be wearing helmets that
have a camera the size of a AA battery on them that will be recording in the direction that the officers
are looking. They record to a utility belt (Batman?), and are said to be high digital quality. The main
reasons for these cameras are for aggressive deterance of anti-social behavior. Mind you, London is
already the camera capital of the world, with the most cameras recording everything ever. These will
also be great for court and evidence, unless more of the LAPD style of arrests keep happening.
Radiation detecting watch
Wednesday, November 15th, 2006
I know what you’re all thinking. When the hell would I ever need this thing? Well, you never know
when the 3rd World War will start, unless you work for the CIA, or maybe you live near a nuclear
reactor, or work for Hazmat, well that’s where you’ll need this thing, so there!!!! Sorry. Along with
47. the regular watch functions this thing just comes with a radiation meter. It will set you back $250 so
start saving. Now it would be cool if it made that white noise sound you hear in the movies when they
are detecting radiation.
Viewsonic Ruggedized Handheld
Wednesday, November 15th, 2006
Viewsonic the makers of all things monitor goodness have decided to come out with not one, but
seven, ah ah ah, Ruggedized handhelds. You know? Count from Sesame…ah forgets it. Here are the
deets and there are a lot of them. The units run on older Windows Mobile 2003 so they can run all
programs created when the PDA boom took off and are powered by Intel XScale processors. The
devices meet IP54 design standards for sealing against dust, moisture and extreme environmental
conditions. The features include 3.5-inch 240 x 320 (QVGA) LCD display, 416MHZ-520MHZ Intel
Xscale processor, Jog dial, SD card slot and swappable Lithium Ion batteries which allow battery
changes without shutdown or loss of data. They also come with 802.11b/g wireless, Bluetooth, bar
code scanner, 1.3 megapixel camera (With most models), fingerprint sensor (with most models) and
GPS (Global Positioning System) support with one model. This thing is loaded and it only weighs 12
oz so it fits in the Christmas stocking very nice like.
48. Fujufilm Face Recognizer
Thursday, November 9th, 2006
FujiFillm just released a new camera that has a facial recognizer in it. It will actually find up to 10
faces in the picture focus on them as a whole and take the best picture possible. It includes 3x Optical
zoom, 6.3 megapixel, intelligent flash, and an image generator that will take pictures adjusted for
uploading to places like My Space that have a lower image size. It also has a 2.5 inch scratch resistant
LCD screen. It comes in a plethora of colors to boot. There is no pricing yet, but it will be available
in January in case you didn’t buy enough during Christmas.
Plastics play an important role in the design of electronic products. It is crucial that engineers
understand the characteristics of plastics in order to select the appropriate plastic for a given
application. Many factors affect this decision, including the required properties and the molding
process. Ultimately, selecting the right plastics can help ensure the safety and reliability of the final
product. Plastic are very promising materials to be used in electronic materials.
Organic electronics are lighter, more flexible, and less expensive than their inorganic counterparts.
They are also biodegradable (being made from carbon, e.g.. melanin).
This opens the door to many exciting and advanced new applications that would be impossible using
copper or silicon.
CHEMICAL BONDING AND CONDUCTIVITY
• WHAT HAPPENED IN THE PA FILM
6. HOW CAN PLASTIC BECOME CONDUCTIVE
MANUFACTURING OF PLASTIC ELECTRONICS
INORGANIC Vs ORGANIC
BENEFITS AND OBSTACLES
CONJUGATED POLYMERS: ELECTRONIC CONDUCTOR
SPECIFYING PLASTIC FOR ELECTRONIC DESIGN
KEY TERMS AND ABBREVATIONS
HOW POLYMER CONDUCTIVITY WAS REAVEALED
DOPING- FOR BETTER MOLECULE PERFORMANCE
WIRELESS DIGITAL PENS AND MOUSE
DIGITAL CAMERA WITH PRINTERS
SELF-ENERGIZING MEDICAL GADGETS
GAMMA RADIATION WATCH
LIFE SAVING TOOL
RADIATION DETECTING WATCH
52. Thank you for your attention…
Materials Matter 2007, Volume 2, 3: Special Issue on Organic Electronics