International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
Organotronics A Substitute for Semiconductor
Technology
Sai Ramakrishna.Badisa#, Suresh Angadi *, Siva Karthik. karavadi#
#
Final Year B.Tech, Dept. of ECE, KL University, Vaddeswaram, AP, India
Address
*
Assistant Professor B.Tech, Dept. of ECE, KL University,
Vaddeswaram, AP, India
ABSTRACT: The word
electronics means study of
steady flow of free electrons. Mostly the flow of
electrons is concerned with semiconductor devices made
up of silicon and germanium. The word organic
electronics deals with the flow of electrons in non
semiconductor namely organic materials. Most of the
organic materials are long chain of single molecules that
are highly adaptable. Due to the conjugation property in
polymers the charges in the organic materials flow
due to which the chain structure becomes electrically
conductive.
This nature of the polymers has revolutnizing the
electronics. They play a prominent role in overcoming
the disadvantages in the use of semiconductor devices.
These conductive polymers are less expensive and more
flexible than inorganic semiconductors. These are more
desirable alternative in many applications and new
applications which are not possible with semiconductor
devices. Organic electronics not only deal with only
organic semiconductors but also with organic dielectrics,
conductors and light emitters.
Polymers are essentially electronic compounds that can
be processed as liquids. With thin fill technology
polymer solutions can be deposited on substrates with
many of industrial process off which ink jet method is
most popular. Applications of the conductive polymers
are OLED, organic photovoltaic cells, plastic memory,
molecular computers, electronics paper and smart
windows. These organic semiconductors have high
resistance which makes them electrically poor
conductors doping methods are usually done to increase
the conductivity.
KEY WORDS: organic semi conductors,conjugation,
conducting polymers, power consumptions and flexibilities,
advantages over conventional semi conductors, applications
of organic semiconductors.
ISSN: 2231-5381
1.
INTRODUCTION
The conducting nature of polymers was first observed in the
compound
polyaniline . From this, concluded that
polycyclic aromatic compounds forms semiconducting
charge transfer complex with halogens. Alan J. Heeger,
Alan G. MacDiarmid, and Hideki Shirakawa were awarded
noble prize for their efforts towards conducting nature of
the polymers. Conduction in polymers comprises two
process mainly delocalization of pi-electrons and resonance
stabilization.
Examples of conductive polymer are
polythiophene, polyaniline, polyacetylene.
POlypyrrole,
A.
ADVANTAGES
SEMICONDUCTORS
INORGANIC
1)
2)
3)
4)
5)
6)
OVER
Light weight
Mechanical flexibility
Chemical modifications possible
Easy and cheap processing
Low power consumption
High efficiency
B. WORKING
Organic compounds conduct mainly due to delocalization of
pi-electrons in pi bonds. The word delocalization means the
property of organic compound by which electrons and holes
move in conjugated system to attain stability when an
electric field is applied across them . Organic
semiconductors contain HOMO (highest occupied
molecular orbital)
and
LUMO (lowest unoccupied
molecular orbital) which are analogous to valence and
conduction band in inorganic semiconductors. The
electricity is caused due to transfer of electrons and photons
from HUMO to LUMO.
http://www.ijettjournal.org
Page 996
International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
C. IMPLANTATION OF ORGANIC COMPOUNDS
In general the organic compounds have to be implanted on
substrates for their purpose to work as a support. There are
many methods to implant organic compounds on substrates
and they are
1.
2.
3.
Ink jet printing
Organic vapor phase deposition(OVPD)
Vacuum thermal evaporation(VTE)
Among the above three , ink jet method is very cheap and
most commonly used technique. This method is same as
paper printing mechanism where the organic layers are
sprayed onto the substrates.
Organic vapor phase deposition (OVPD) is of low cost. In
this method a cooled substrate is being hit by the organic
molecules
are evaporated in a low pressure, high
temperature chamber. This gas is carried onto the substrate
with the help of a carrier gas.
In vacuum thermal deposition (VTD) method organic
molecules are gently heated so that they evaporate and
subside on substrate.
II. ORGANIC LIGHT EMITTING DIODES
OLEDs are simple solid state devices that work on the
principle of ELECTRO-LUMINESCENCE. They comprise
very thin films of organic compounds in the electroluminescent layer. These organic compounds are to be
designed in between electrodes. One among the electrodes
must be transparent and the resultant is a very bright and
crispy display with less power consumption than usual LCD
and LED.
A. STRUCTURE
An OLED mainly consists of following parts
1) Substrate
2) Electrodes
3) Organic layers
Substrate is the material on which the organic compounds
are implanted. Commonly used may be plastic, foil or even
glass.
Fig 1.1 structure of OLED
Electrodes comprise cathode and anode. Cathode must have
great work function which helps in injecting holes into
different layers and usually used is indium tin oxide(ITO).
The cathode component must have lesser work function
than anodes which help in injecting electrons into different
layers. Emissive layer is made up of polyfluorene .
Conductive layer is usually made up of polyaniline.
B. TYPES OF OLED
There are many types of OLED each have many advantages
in present day life. They are
1) Passive matrix ,
2) Active matrix ,
3) Inverted ,
4) Foldable ,
5) Top emitting ,
6) Transparent ,
7) Stacked OLED.
C. ADVANTAGES OVER LED AND LCD
1) Like LCD , the OLED doesn’t require a backlight
for its normal working. This makes them more
advantageous in saving space and also weight.
2) OLED is also capable of making high contrast
ration in dark regions. Thickness of OLED is 200
times smaller than LED.
3) Refresh time of OLED is far less than LED and
LCD.
4) They can be used in fabrication of clothes,
manufacturing is highly commercial and
economical.
D. DISADVANTAGES
1) The life time of OLED is very less ,
2) The colour of the display by time,
3) These are not water resistant.
ISSN: 2231-5381
http://www.ijettjournal.org
Page 997
International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
Applications : Oled’s are used as mobile phone
screens,MP3players,digital cameras, car radios, PDA’s and
so on .
crystalinity of the organic material we can achieve higher
mobility.
V. DRAWBACKS OF ORGANIC SEMICONDUCTORS
POOR CRYSTALINITY:
III. ORGANIC PHOTO VOLTAIC CELL
With increase of human needs there arose a need of lot
many resources that are becoming scarce, that satisfy human
wants. Shifting from non conventional energy sources to
renewable energy sources is the only option to escape from
above crisis. Organic photo voltaic cells have became one
among the best one two utilize aforesaid renewable energy
source in an efficient way.
Instead of semiconductor layer in between the two
electrodes two organic layers made of different materials
are placed in OVPC. Cells using single organic layer gives
low mobility.
Poor crystalinity is the main drawback of organic
compounds that has its impacts on many other properties
like mobility.
LOW MOBILITY:
1) Weak inter-molecular coupling
2) Amorphous nature of organic compounds cause
thermally activated hopping transport, no band
transport
3) Poly-crystalline of the material causes scattering at
grain boundaries
DEGRADATION:
1) Organic compounds can be easily degraded with
environmental influences.
2) These materials are not water resistant
Above two factors with combination of others may cause
life time of the organic semiconductors to be less.
VI. CONCLUSION
A. WORKING
Working of OPVC occurs in 4 stages they are mainly
1) Formation of Exciton
2) Diffusion of Exciton to organic-organic interface
3) Dissociation of exciton
4) Collection of charge carriers at electrodes
Organic solar cells produce a significant amount of
electricity in diffused light. Life span of these OPVC is less
when compared with that of conventional solar cells.
IV. ORGANIC THIN FILM TRANSISTORS
They differ from ordinary FET in the channel. In FET
channel is made up of metal oxide compound. In OTFT
channel is made up of organic material. This differs from
the conventional transistor where the semiconductor
material typically is the substrate.
Formation of positive charge accumulation
semiconductor-insulator interface upon application
positive voltage at GATE. Even though gate voltage is
applied low conductivity is seen. With increase
ISSN: 2231-5381
Organic semiconductor technology is the latest technology
that replaces semiconductor technology in many areas.
Organic semiconductors offer a low cost alternative to
established semiconductors when it comes to large area and
low cost applications. First OLED applications are already
on the market. OTFTs and OPVCs will most probably
follow. Improvements on the material side are still needed.
REFERENCES
[1]
http://en.wikipedia.org/wiki/Organic_electronics
[2]
http://www.orgworld.de/
[3]
http://www.organicsemiconductors.com/
[4]
http://www.newelectronics.co.uk/electronicstechnology/
[5]
http://en.wikipedia.org/wiki/Conductive_polymer
[6]
http://www.sciencedirect.com/science/article
[7]
Book on Organic Electronics Series: Advances
in Polymer Science, Vol. 223Meller, Gregor;
Grasser, Tibor (Eds.) 2010, XIV, 330 p.
[8]
http://www.wmich.edu/
at
of
not
in
http://www.ijettjournal.org
Page 998
International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
BIOGRAPHY
Badisa Sai Ram Krishna was born in 1992
in Krishna District. He is currently
pursing B.Tech from K L University. He
is interested in Telecommunications and
electronics.
Email:
ramkrishna.341@gmail.com
Suresh Angadi* is presently working as
a Asst.Professor in K L University. He
received his B.Tech degree in electronics
and communication in G.V.P College of
Engineering, vizag, 2007 and completed
M.Tech in Maulana Azad National Institute
of Technology in 2009, Bhopal.
Karavadi Siva Karthik# was born in 1991
in Krishna District. He is currently
pursing B.Tech Electronics degree from
K L University. He is interested in
electronics and Tele- Communication.
Email:karthik.karavadi@live.in
ISSN: 2231-5381
http://www.ijettjournal.org
Page 999