Intro

Charge transfer complexes

Conducting polymers

Organic light emitting diodes

Present scenario

Organic electronic materialsby SUNNY TANTIA R on 11/11/09

OLE

D

INTRO:

•ORGANIC

ELECTRONICS is the

branch of electronics that deals with conductive polymers and plastics

•Organic electronic and their hybrid

materials posses

conducting

,semiconducting and

light emitting

properties

•There active

materials are

processed over large

areas of plastic or

paper at lower

temperatures

•Organic electronics are lighter, more flexible ,less

expensive, biodegradable

ORGANIC ELECTRONICS

APPLICATIONS

Field Effect

Transistors[FE

T]

RFID[Radio

Frequency

Identification

] and optical

communicati

on

CHARGE TRANSFER COMPLEX AND CONDUCTIVE

POLYMERS

Charge transfer complex

Conducting polymers

Organic

electronic

materials

CHARGE TRANSFER COMPLEXES

CT complexes are molecular groups where one is electron donating(donor) and

other is electron accepting(acceptor).

There is a partial transfer of electronic charge from donor to the acceptor in the

excited molecular state. CT complexes have transition between excited molecular

state and ground state.

In 1973, a CT complex of TTF-TCNQ was the first organic conductor discovered,

where TTF and

DONOR ACCEPTOR

TCNQ are stacked independently and electron transfer from donor to acceptor

takes place.

Charge transfers are also observed between transition metal ions and ligands.

A ligand metal charge transfer takes place when electrons are donated from Ligands to high oxidation state Metal Centre[LMCT] (e.g.., intense purple color of a

solution of permanganate)

The reverse, a Metal-to-Ligand Charge Transfer[MLCT] occurs when ligands

containing accessible antibonding metal orbital's are coordinated with electron rich metal centre’s.

In 1980, first organic superconducting polymer called Tetra methyl

tetraselenafulvalene-phosphorous –hexafluoride TMTSF2PF6 was discovered with a

superconducting capacity at 0.9K at a pressure of 12kbar.

CONDUCTING

POLYMERS

POLYMERS AND MOLECULES

sp2 HYBRIDISED:σ and π bounds

Conjugated polymers Small

molecules

Conductive polymers are organic semiconductors including

polyacetylenes, polypyrroles, polythiophenes, polyanilines,polyflurenes,polynaphthale

nes, poly p-phenylene sulphide, poly p-phenylene vinylene .

Melanin pigment in animals is a mixed copolymer of polyacetylene, polypyrrole, polyaniline.

Fungal melanins are pure polyacetylenes and hence they are often called as MELANINS

or ‘BLACKS’

Conductive organic polymers have extended delocalized bonds similar to band structures

in silicon but with localized states.

Electronic conductivity can be increased by introducing charge carriers in valence or

conduction band[DOPING]

Delocalization can be accomplished by formation of conjugated backbone of continuous

overlapping orbital's(e.g.., alternating single and double C-C bond can form a continuous

path of overlapping p-orbital’s.In polyacetylenes this creates degeneracy in the frontier

molecular orbital's[highest occupied and lowest unoccupied orbital’s namely HOMO and

LUMO . This leads to filled(electron containing) and unfilled bands similar to valence and

conduction bands in semiconductors).

Conduction mechanisms involves resonance stabilization, delocalization of pi- electrons

along entire polymer backbones, as well as mobility gaps ,tunneling and phonon assisted

hopping.

Tunneling is the quantum mechanical process

by which a particle can penetrate a classically

forbidden region of space

Frequency hopping is one of two

basic modulation techniques

used in spread spectrum signal

transmission. It is the repeated

switching of frequencies during

radio transmission, often to

minimize the effectiveness of

"electronic warfare" - that is, the

unauthorized interception or

jamming of telecommunications.

Molecular orbital’s:

An OLED is a thin film LED in which the emissive layer is an organic

compound.

When this layer is polymeric (or plastic), OLEDs can be deposited in rows and

columns on a screen using simple printing methods that are much more

efficient than those used in manufacturing traditional LEDs.

A key benefit of OLEDs is that they don’t need a backlight to function.

An electron and hole pair is generated inside the emissive layer. When the

electron and hole combine, a photon is produced, which will show up as a dot

of light on the screen. Many OLEDs together on a screen make up a picture.

FLEXIBLE OLED and OTFT’s

•The men principally credited for the discovery and development of highly-

conductive organic polymers (atleast 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.

Nobel price

in chemistry

2000 !!!… are

rewarded “for

the discovery

and

development

of electrically

conductive

polymers”.

Present scenario:Transformation of

TECHNOLOGY!!!

Thank You for your attention!!