21199573 Light Emitting Polymer

8/12/2019 21199573 Light Emitting Polymer

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Seminar report Light Emitting Polymer

ABSTRACT

The seminar is about polymers that can emit light when a voltage is

applied to it. The structure comprises of a thin film of semiconducting polymer

sandwiched between two electrodes (cathode and anode).When electrons and

holes are inected from the electrodes! the recombination of these charge

carriers ta"es place! which leads to emission of light .The band gap! ie. The

energy difference between valence band and conduction band determines the

wavelength (colour) of the emitted light.

They are usually made by in" et printing process. #n this method red

green and blue polymer solutions are etted into well defined areas on the

substrate. This is because! PLE$s are soluble in common organic solvents li"e

toluene and %ylene .The film thic"ness uniformity is obtained by multi&passing

(slow) is by heads with drive per no''le technology .The pi%els are controlled

by using active or passive matri%.

The advantages include low cost! small si'e! no viewing angle

restrictions! low power reuirement! biodegradability etc. They are poised to

replace L$s used in laptops and *Ts used in des"top computers today.

Their future applications include fle%ible displays which can be folded!

wearable displays with interactive features! camouflage etc.

+

Electronics , communication gptc.nta


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INTRODUCTION

-fter watching the brea"fast news on T! you roll up the set li"e a

large hand"erchief! and stuff it into your briefcase. /n the bus or train

ourney to your office! you can pull it out and catch up with the latest

stoc" mar"et uotes on 01.

& Somewhere in the 2argil sector! a platoon commander of the

#ndian -rmy readies for the regular satellite updates that will give him

the latest terrain pictures of the border in his sector. 3e unrolls a plastic&li"e map and hoo"s it to the unit4s satellite telephone. #n seconds! the map

is refreshed with the latest high resolution camera images grabbed by an

#ndian satellite which passed over the region ust minutes ago.

$on5t imagine these scenarios at least not for too long.The current

67 billion&dollar display mar"et! dominated by L$s (standard in

laptops) and cathode ray tubes (*Ts! standard in televisions)! is seeingthe introduction of full&color LEP&driven displays that are more efficient!

brighter! and easier to manufacture. #t is possible that organic light&

emitting materials will replace older display technologies much li"e

compact discs have relegated cassette tapes to storage bins.

The origins of polymer /LE$ technology go bac" to the discovery of

conducting polymers in +899!which earned the co&discoverers& -lan :.

3eeger ! -lan ;.


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HISTORY OF LIGHT EMITING POLYMER

Polymers

igures + and = below.

>igure +B The double&bonded precursor to polyethyleneBethylene

>igure =B The single&bonded polymer polyethylene

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Polymers e%ist in many varieties ranging from the very simple repeating

patterns of chains of monomers! to the somewhat more sophisticated molecular

patterns as found in copolymersD polymers composed of two or more chemically

distinguishable monomers. opolymers! in turn! can e%ist in many conurations!

owing to the many ways the individual monomers can be ordered. There are

bloc" polymers! in which large sections are repeated along the polymer chain

graft polymers where another polymer is attached as a side chain random

polymers where the deferent monomer units ta"e on! as the name suggests a

random ordering to form the polymer chain and so on. -nother important class

of polymers is conugated polymers. onugated polymers consist of carbon

bac"bones with alternating single and double bonds and have shown great

potential as light emitting materials.

The first organic electroluminescent devices were discovered around the

time the first light emitting diodes (LE$s) were introduced into the ommercial

mar"et in +8F=. Li"e today! early devices were hampered by fabrication and

pac"aging problems and short lifetimes Electroluminescence (EL) was first

observed in conugated polymers in +887 by 1urroughs et al. ! which reveals the

relative youth of this field. Evidence for electro luminescence from the seminalpaper by 1urroughs et al. is shown in >igure C.

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Figure 3: Electroluminescence in PPV. From Burroughs[4]

Prior to this! electroluminescence had been witnessed in organic

molecules by Tang and an Sly"e in +8G9! who revived interest in organic EL.

-ll of these were originally preceded by the wor" of Partridge in +8GC ! whose

wor" largely went unnoticed. Since the advent of electroluminescent polymers!

conugated polymeric materials with emissions spanning the broad spectrum of

visible and non&visible radiation (near infrared) have been fabricated! as shown

in >igure 6. - voltage tunable&luminescent device has been fabricated using

poly (thiophene) blends. /ne group has created white&light devices by using

appropriate combinations of these EL materials.


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SUBJECT DETAILING

LIGHT EMITTING POLYMER

#t is a polymer that emits light when a voltage is applied to it. The

structure comprises a thin&film of semiconducting polymer sandwiched

between two electrodes (anode and cathode) as shown in fig.+. When

electrons and holes are inected from the electrodes! the recombination of

these charge carriers ta"es place! which leads to emission of light that

escapes through glass substrate. The band gap! i.e. energy difference

between valence band and conduction band of the semiconducting polymer

determines the wavelength (colour) of the emitted light.

Characterization of light-emitting polymer

Light&emitting polymer technology is set to open a complete new world

of applications for a wide range of products! such as small (and eventually

large) flat screen displays! warning signs! decorative lighting and illuminated

advertising +!=. The active layer of polymer&LE$s can be prepared by simple

coating methods! such as spin coating. -ll colors are now available for these

displays which can be made as thin as one millimeter. 3igh brightness can be

achieved at low power

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onsumption and long life times of more than C7777 hours. Light

emitting polymers are organic! conugated! macromolecules of very high

molecular weight. -n important e%ample are phenyl&substituted poly(p&

phenylene vinylene) (PP). To ma"e them soluble and to process them into thin

films they are modified! for e%ample! by introducing al"yl or al"o%y side

chains. >igure + shows the structure of a commercially available phenyl

al"o%yphenyl PP copolymer. The compound is soluble in aromatic

hydrocarbons! cyclic ethers and certain "etons.The uality of the film coating

process (and thus also the resulting polymer&LE$) strongly depends on the

polymeri'ation and the resulting molecular weight dataImolecular weight

distribution. The latter parameters can be monitored

+. Structure of phenyl al"o%yphenyl PP copolymer

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=./verlay of chromatograms obtained simultaneously by diode array

and refractive inde% detection settingIevaluation

Conditions

Sample preparation

Samples were dissolved in stabli'ed T3>

and filtered (concentration 7.+ J)

Column

C K PL;el mi%ed ! 9.H K C77 mm! H m

(-gilent pIn 988++;P&igure = shows an overlay of the diode array and

refractive inde% detector signals of a phenyl al"o%yphenyl PP copolymer

analysis. The chromatograms and the ;P report obtained with the

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hemStation ;P data analysis software (figure C) show the high uality

resulting fromB

O 1road molecular weight distribution ranging from about +7C to 9K+7F $alton

O Large polydispersity $ of about C.9

O ery high molecular weight averages! e.g.


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CONSTRUCTION

Light emittingdevices concict of active emitting layer sandwiched between

an cathode and a anode indium tin o%ide s typically used for the anode and

aluminum or calcium of the cathode fig=.+(a) shows the structure of a simple

single layer device with electrodes and an active layer. Single&layer devices

typically wor" only under a forward $ bias. >ig.=.+ (b) shows a

symmetrically configured alternating current light&emitting (S-LE) device

that wor"s under - as well as forward and rivers $ bias.

#n order to manufacture the polymer! a spin&coating machine is used that

has a plate spinning at the speed of a few thousand rotations per minute. The

robot pours the plastic over the rotating plate! which! in turn! evenly spreads the

polymer on the plate. This results in an e%tremely fine layer of the polymer

having a thic"ness of +77 nanometers. /nce the polymer is evenly spread! it is

ba"ed in an oven to evaporate any remnant liuid. The same technology is used

to coat the $s.

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INK JT PRINTIN!

-lthough in"et printing is well established in printing graphic

images! only now are applications emerging in printing electronics

materials. -ppro%imately a do'en companies have demonstrated the use of

in"et

printing for PLE$ displays and this techniue is now at the forefront of

developments in digital electronic materials deposition. 3owever! turning

in"et printing into a manufacturing process for PLE$ displays has reuired

significant developments of the in"et print head! the in"s and the substrates

(see >ig.=.+.+).reating a full colour! in"et printed display reuires the

precise metering of volumes in the order of pico liters. *ed! green and blue

polymer solutions are etted into well defined areas with an angle of flight

deviation of less than HQ. To ensure the displays have uniform emission! the

film thic"ness has to be very uniform.

>ig. =.+.+ Schematic of the in" et printing for PLE$ materials

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>or some materials and display applications the film thic"ness

uniformity may have to be better than R= per cent. - conventional in"et

head may have volume variations of up to R=7 per cent from the hundred or

so no''les that comprise the head and! in the worst case! a no''le may be

bloc"ed. >or graphic art this variation can be averaged out by multi&passing

with the uality to the print dependent on the number of passes. -lthough

multi&passing could be used for PLE$s the process would be unacceptably

slow. *ecently! Spectra! the world5s largest supplier of industrial in"et

heads! has started to manufacture heads where the drive conditions for each

no''le can be adusted individually so called drive&per&no''le ($P0).

Litre% in the ?S-! a subsidiary of $T! has developed software to allow

$P0 to be used in its printers. olume variations across the head of R= per

cent can be achieved using $P0. #n addition to very good volume control!

the head has been designed to give drops of in" with a very small angle&of&

flight variation. - =77 dots per inch (dpi) display has colour pi%els only 67

microns wide the latest print heads have a deviation of less than RH microns

when placed 7.H mm from the substrate. #n addition to the precision of the

print head! the formulation of the in" is "ey to ma"ing effective and

attractive display devices. The formulation of a dry polymer material into an

in" suitable for PLE$ displays reuires that the in"ets reliably at high

freuency and that on reaching the surface of the substrate! forms a wet film

in the correct location and dries to a uniformly flat film. The film then has toperform as a useful electro&optical material. *ecent progress in in"

formulation and printer technology has allowed 677 mm panels to be colour

printed

"CTI# "N$ P"SSI# %"TRI&


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diode such as a PLE$! capable of emitting light by being turned on or off! or

any state in between. oloured displays are formed by positioning matrices

of red! green and blue pi%els very close together. To control the pi%els!

and so form the image reuired! either 4passive4 or 4active4 matri% driver

methods are used.

Pi%el displays can either by active or passive matri%. >ig. =.+.=

shows the differences between the two matri% types! active displays have

transistors so that when a particular pi%el is turned on it remains on until it isturned off.

The matri% pi%els are accessed seuentially. -s a result passive

displays are prone to flic"ering since each pi%el only emits light for such a

small length of time. -ctive displays are preferred! however it is technically

challenging to incorporate so many transistors into such small a compact

area.

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>ig =.+.= -ctive and passive matrices

#n passive matri% systems! each row and each column of the display

has its own driver! and to create an image! the matri% is rapidly scanned to

enable every pi%el to be switched on or off as reuired. -s the current

reuired to brighten a pi%el increases (for higher brightness displays)! and as

the display gets larger! this process becomes more difficult since higher

currents have to flow down the control lines. -lso! the controlling current

has to be present whenever the pi%el is reuired to light up. -s a result!

passive matri% displays tend to be used mainly where cheap! simple displays

are reuired

-ctive matri% displays solve the problem of efficiently addressing

each pi%el by incorporating a transistor (T>T) in series with each pi%el which

provides control over the current and hence the brightness of individual

pi%el.

Lower currents can now flow down the control wires since this have

only to program the T>T driver ! and the wires can be finer as a result .also!

the transistor is able to hold the current setting! "eeping the pi%el at the

reuired brightness! until it receives another control signal . >uture demands

on displays will in path reuire larger area displays so the active matri%

mar"ed segment will grow faster.

PLE$ devises are especially suitable for incorporating into active

matri% displays! as they are processeble in solution and! can be manufactured

using in" get printing over larger areas.

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'"SIC PRINCIP( "N$ TC)NO(O!*

Polymer properties are dominated by the covalent nature of carbon

bonds ma"ing up the organic molecules bac"bone. The immobility of

electrons that form the covalent bonds e%plain why plastics were classified

almost e%clusively insulators until the +8975s.

- single carbon&carbon bond is composed of two electrons being

shared in overlapping wave functions. >or each carbon! the four electrons in

the valence bond form tetrahedral oriented hybridi'ed spC orbital5s from the s

, p orbital5s described uantum mechanically as geometrical wave

functions.

The properties of the spherical s orbital and bimodal p orbital5s combine into

four eual! unsymmetrical! tetrahedral oriented hybridi'ed spC orbitals. The

bond formed by the overlap of these hybridi'ed orbitals from two carbon

atoms is referred to as a sigma5 bond.

- conugated pi5 bond refers to a carbon chain or ring whose bonds

alternate between single and double (or triple) bonds. The bonding system

tend to form stronger bonds than might be first indicated by a structure withsingle bonds.

The single bond formed between two double bonds inherits the

characteristics of the double bonds since the single bond is formed by two

sp= hybrid orbitals. The p orbitals of the single bonded carbons form an

effective pi5 bond ultimately leading to the significant conseuence of pi5

electron de&locali'ation.

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?nli"e the sigma5 bond electrons! which are trapped between the carbons!

the pi5 bond electrons have relative mobility. -ll that is reuired to provide

an effective conducting band is the o%idation or reduction of carbons in the

bac"bone. Then the electrons have mobility! as do the holes generated by the

absence of electrons through o%idation with a dopant li"e iodine.

BASIC STRUCTURE AND WORKING

-n LEP display solely consists of the polymer material manufactured on

a substrate of glass or plastic and doesn5t reuire additional elements li"e

polari'es that are typical of L$s. LEP emits light as a function of its electrical

operation.

The basic LEP consists of a stac" of thin organic polymer layers

sandwiched between a transport anode and a metallic cathode. >igure shows the

basic structure. The indium&tin&o%ide (#T/) coated glass is coated with a

polymer. /n the top of it! there is a metal electrode of -l! Li!


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Two types of displaysB The LEP displays are two types! namely! passive

matri% and active matri%. To drive a passive matri% display! the current is

passed through select pi%els by applying a voltage to the drivers attached to the

corresponding rows and columns. These schemes pattern the anode and cathode

into perpendicular rows and columns and apply a data signal to the columns

while addressing the seuentially. -s the number of rows in the display

increases! each pi%el must be red brightness by a factor of the number or row

times the desired brightness! which can e%ceed =7777cdIm=.the current reuired

to achieve this brightness! levels limits this architecture to relatively smallscreen si'es. Philips >lat $isplay systems (Sunnyvale! -) and $uPont

$isplays have demonstrated full&colour passive matri% displays. #n active matri%

architecture! a thin film polysilicon transistor on the substrate addresses each

pi%el individually. -ctive matri% displays are not limited by current

consideration. Sei"o& Epson! Toshiba (To"yo! :apan)! and Samsung (Seoul!

2orea) have now demonstrated full colour active matri% displays. /ne e%citing

possibility is that polymer transistors! which can be

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Light&Emitting Polymers manufacturedby techniues similar to those used

for LEP patterning! could be used to drive an LEP display. Such an approach would

potentially lend itself to roll&to&roll processing on fle%ible substrates.

Performance table of different colours of LEP

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(I!)T %ISSION

The production of photons from the energy gap of a material is very

similar for organic and ceramic semiconductors. 3ence a brief description of

the process of electroluminescence is in order.

Electroluminescence is the process in which electromagnetic(E


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With non&organic semiconductors there is a band gap associated with

1rillion 'ones that discrete electron energies based on the periodic order of

the crystalline lattice. The free electron5s mobility from lattice site to lattice

site is clearly sensitive to the long&term order of the material. This is not so

for the organic semiconductor. The energy gap of the polymer is more a

function of the individual bac"bone! and the mobility of electrons and holes

are limited to the linear or branched directions of the molecule they

statistically inhabit. The efficiency of electronIhole transport between

polymer molecules is also uniue to polymers. Electron and hole mobility

occurs as a hopping5 mechanism which is significant to the practical

development of organic emitting devices.

PP has a fully conugated bac"bone (figure +)! as a conseuence the

3/


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PP is a semiconductor. Semiconductors are so called because they have

conductivity that is midway between that of a conductor and an insulator. While

conductors such as copper conduct electricity with little to no energy (in this

case potential difference or voltage) reuired to V"ic"&startV a current! insulators

such as glass reuire huge amounts of energy to conduct a current. Semi&

conductors reuire modest amounts of energy in order to carry a current! and are

used in technologies such as transistors! microchips and LE$s.

1and theory is used to e%plain the semi&conductance of PP! see figure

H. #n a diatomic molecule! a molecular orbital (


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>igure =.=.= - series of orbital diagrams.

O - diatomic molecule has a bonding and an anti&bonding orbital!

two atomic orbital5s gives two molecular orbital5s. The electrons arrange

themselves following! -uf 1au and the Pauli Principle.

O - single atom has one atomic orbital

O - tri atomic molecule has three molecular orbitals! as before one

bonding! one anti&bonding! and in addition one non&bonding orbital.

O >our atomic orbitals give four molecular orbitals.

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#t is already apparent that conduction in polymers is not similar to that

of metals and inorganic conductors however there is more to this story@ >irst

we need to imagine a conventional diode system! i.e. PP sandwiched

between an electron inector (or cathode)! and an anode. The electron

inector needs to inect electrons of sufficient energy to e%ceed the band gap

the anode operates by removing electrons from the polymer and

conseuently leaving regions of positive charge called holes. The anode is

conseuently referred to as the hole inector.

#n this model! holes and electrons are referred to as charge carriers

both are free to traverse the PP chains and as a result will come into

contact. #t is logical for an electron to fill a hole when the opportunity is

presented and they are said to capture one another. The capture of oppositely

charged carriers is referred to as recombination. When captured! an electron

and a hole form neutral&bound e%cited states (termed e%citons) that uic"ly

decay and produce a photon up to =HJ of the time! 9HJ of the time! decay

produces only heat! this is due to the the possible multiplicities of the

e%citon. The freuency of the photon is tied to the band&gap of the polymer

PP has a band&gap of =.=e! which corresponds to yellow&green light.

0ot all conducting polymers fluoresce! polyacetylene! one of the first

conducting&polymers to be discovered was found to fluoresce at e%tremely low

levels of intensity. E%citons are still captured and still decay! however they

mostly decay to release heat. This is what you may have e%pected since

electrical resistance in most conductors causes the conductor to become hot.

apture is essential for a current to be sustained. Without capture the

charge densities of holes and electrons would build up! uic"ly preventing

any inection of charge carriers. #n effect no current would flow.

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/


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Liuid rystal

$isplay

L$ *eflective -n L$ uses

the properties of

liuid crystals in

an electric fieldto guide light

from oppositely

polari'ed front

and bac" display

plates. The

liuid crystal

wor"s as a

helical director

(when the driver

presents the

correct electric

field) to guidethe light through

87N from one

plate

Small! static!

mono panels can

be very low cost

1oth mono andcolor panels

widely available

1ac"light adds

cost! and often

limits the useful

life

*euires -

drive waveform

>ragile unless

C)%ISTR* ')IN$ (P

LEPs are constructed from a special class of polymers called conugated

polymers. Plastic materials with metallic and semiconductor characteristics are

called conugated polymers. These polymers posses delocali'ed pi electrons

along the bac"bone! whose mobility shows properties of semiconductors.

-lso this gives it the ability to support positive and negative carriers with high

mobility along the polymer chain. The charge transport mechanism in

conugated polymers is different from traditional inorganic semiconductors. The

amorphous chain morphology results in inhomogeneous Light&Emitting

Polymers broadening of the energies of the chain segments and leads to hopping

type transport. onugated polymers have already found application as

conductor in battery electrodes! transparent conductive coatings! capacitor

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electrolytes and through hole platting in P15s. There are fast displaying

traditional materials such as natural polymers etc owing to better physical and

mechanical properties and amenability to various processes.

%"NUF"CTURIN!

#n order to manufacture the polymer two techniues is used. Spin coating

process This techniue involves spinning a dis"! that is glass substrate at a fi%ed

angular velocity and letting a small amount of polymer solution to drop on the

top of the dis". #t is shown in the figure. Spin coating machine used has a few

thousands rotations per minute. The robot pours the plastic over the rotating

plate! which in turn! evenly spreads the polymer on the plate. This results in an

e%tremely fine layer of the polymer having a thic"ness of +77 nanometers. /nce

the polymer is evenly spread! it is a[ba"ed in an oven to evaporate any remnant

liuid


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Printing of patterned IT anodes:

The aim was the development of a patterned anode of transparent

conducting #T/ on PET foils by a printing process based on #T/ nano particle

dispersions. The #T/ patterns thus prepared were to be used as transparent

anodes in PLE$ devices structures. ). 1efore the start of this proect! crystalline

#T/ nano particles had been developed and dispersed in different solvents

mainly for large area coating (e.g. by spin coating).6 1y addition of a small

amount of a polymeri'able hydroly'ed silane and a photo starter! transparent

conducting #T/ coatings were thus obtained on plastic substrates including foils

by a ?&curing at low temperatures (\+C7N) with a sheet resistance of = to H

"]s and a transmittance of 87 J in the visible range (thic"ness H77 nm). -

post treatment under reducing conditions (0=I3=) at low temperatures (\+C7N)

resulted in a further decrease in the sheet resistance below +ohm s

(a) (b)

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(c)

Photographs of a) the lab&scale gravure printing machine! b) the gravure plate

with different patterns (areas are C9%+=9 mm=in si'e)! and c) the diamond&

engraved cells pattern (++7 linesIcm).

#n a first set of e%periments it was intended to obtain full&tone printed

areas with a high thic"ness homogeneity using a lab&scale gravure printer fortesting (>igure =a! Labratester & 0. Schl^fli igure =b , =c! C9K+=9 mm= each) in order to find the

wor"ing parameters for #T/ coatings such as the feasible printing speed or the

characteristics of the gravure cavities. #n general! film formation in gravure

printing reuires a coalescence of adacent! single liuid dots while at the same

time! however! a spreading of the liuid droplets or of the film beyond this

coalescence has to be avoided to retain the printed structures.H This reuires an

elaborate adustment of the rheological properties of the printing in"s and a

thorough control of film drying. Typical printing speeds up to 67 mImin thus

could be reali'ed without loss of homogeneity. While homogeneous coatings

could be generally obtained for line densities ranging from 67 to =+7 linesIcm!

this parameter also fundamentally determines the thic"ness of the resulting

coatings as the volume of the engraved cavities is decreasing with the line

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density. #n view of the final application to a direct patterning! however! this

means that a compromise has to

be found between the desired coating thic"ness and the reuired

resolution of the printing as the theology of the in"s can only be varied in

certain limits mainly given by the limitation in the solid content and by

problems arising from the use of printing additives.H $epending on the #T/

solid content in the in"s and the geometry of the gravure cells! thus thic"nesses

ranging from 7.= to more than + m were reali'ed in a single printing step.

$ifferent #T/ in"s based on solvents with medium and high boiling points were

tested. #n addition! comparative e%periments with different surface modifiers for

#T/ were initiated to minimi'e the interaction between the particles during film

formation as a maor reuirement for optically transparent coatings. The total

content of solvents and additives in the printing in" generally is a very

important parameter for coating uality! as it also influences the film drying and

determines the content of organic residues in the resulting #T/ film and hence

the porosity.

"$#"NT"!S

O *euire only C.C volts and have lifetime of more than C7!777

hours.

O Low power consumption.O Self luminous.

O 0o viewing angle dependence.

O $isplay fast moving images with optimum clarity.

O ost much less to manufacture and to run than *Ts because the

active material is plastic.

O an be scaled to any dimension.

O >ast switching speeds that are typical of LE$s.

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O 0o environmental draw bac"s.

O 0o power in ta"e when switched off.

O -ll colours of the visible spectrum are possible by appropriate

choose of polymers.

O Simple to use technology than conventional solid state LE$s and

lasers.

O ery slim flat panel.

They don5t additional elements li"e the bac"lights! filters

and polari'es that are typical of L$s.

DISADVANTAGES

O ulnerable to shorts due to contamination of substrate surface by

dust.

O oltage drops.

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disintegrate. The solution was to do the final soldering in a glass ar filled

nitrogen. The enclosure protects the device from impurities and provides a

higher degree of efficiency by giving the screen an estimated life span of C7!777

wor"ing hours.

=. Space charge effect:

The effect of space charge on the voltage&current characteristics and

current&voltage characteristics becomes more pronounced when the difference

in the electron hole nobilities is increased. onseuences of space charge

include lowering of the electric fields near the contacts and therefore

suppression of the inected tunnel currents and strongly asymmetric

recombination profiles for uneual mobility thereby decreasing the

luminescence and hence decreases the efficiency. *esearch is underway to

overcome this barrier Even though this limitations are there LEPs found to be

superior to other flat panel displays li"e L$! >E$ (field emission display) and

etc.

APPLICATIONS AND FEURE DEVELOPMENTS

Al!"#$!o%sB

Polymer light&emitting diodes (PLE$) can easily be processed into large&

area thin films using simple and ine%pensive technology. They also promise to

challenge L$4s as the premiere display technology for wireless phones! pagers!

and P$-4s with brighter! thinner! lighter! and faster features than the current

display.

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P)OTO#O(T"ICS

$T5s PLE$ technology can be used in reverse! to convert light into

electricity. $evices which convert light into electricity are called photovoltaic

(P) devices! and are at the heart of solar cells and light detectors. $T has an

active program to develop efficient solar cells and light detectors using its

polymer semiconductor "now&how and e%perience! and has filed several patents

in the area.

$igital cloc"s powered by $T4s polymer solar cells.

PO(* ($ T#

Philips will demonstrate its first +C&inch PolyLE$ T prototype based on

polymer /LE$ (organic light&emitting diode) technology Ta"ing as its

reference application the wide&screen C7&inch diagonal display with WM;-

(+CFH%9FG) resolution! Philips has produced a prototype +C&inch carve&out of

this display (resolution H9F%C=6) to demonstrate the feasibility of

manufacturing large&screen polymer /LE$ displays using high&accuracy multi&

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no''le! multi&head in"et printers. The e%cellent and spar"ling image uality of

Philips4 Poly LE$ T prototype illustrates the great potential of this new

display technology for T applications. -ccording to current predictions! a

polymer /LE$&based T could be a reality in the ne%t five years.

'"'* %O'I(

This award winning baby mobile uses light weight organic light emitting

diodes to reali'e images and sounds in response to gestures and speech of the

infant.

CC



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%P. P("*R $ISP("*

-nother product on the mar"et ta"ing advantage of a thin form&factor! light&

emitting polymer display is the new! compact!


35/39


3igh efficiency displays running on low power and economical to

manufacture will find many uses in the consumer electronics field. 1right! clear

screens filled with information and entertainment data of all sorts may ma"e our

lives easier! happier and safer.

$emands for information on the move could drive the development of

4wearable4 displays! with interactive features.

Eywith changing information ole wool gives many brand ownerve edge

CH



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The ability of PLE$s to be fabricated on fle%ible substrates opens up

fascinating possibilities for formable or even fully fle%ible displays e catching

pac"aging intent at the point of a valuable competition

F/ %OR $#(OP%NTS

O 1ecause the plastics can be made in the form of thin films or

sheets! they offer a huge range of applications. These include television

or computer screens that can be rolled up and tossed in a briefcase! and

cheap videophones.

O lothes made of the polymer and powered by a small battery

pac" could provide their own cinema show.

O amouflage! generating an image of its surroundings pic"ed up

by a camera would allow its wearer to blend perfectly into the

bac"ground

O - fully integrated analytical chip that contains an integrated light

source and detector could provide powerful point&of&care technology.

This would greatly e%tend the tools available to a doctor and would allow

on&the&spot uantitative analysis! eliminating the need for patients to

ma"e repeat visits. This would bring forward the start of treatment! lower

treatment costs and free up clinician time.

CF



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The future is bright for products incorporating PLE$ displays. ?ltra&light! ultra&

thin displays! with low power consumption and e%cellent readability allow

product designers a much freer rein. The environmentally conscious will warm

to the absence of to%ic substances and lower overall material reuirements of

PLE$s! and it would not be an e%aggeration to say that all current display

applications could benefit from the introduction of PLE$ technology.

$T sees PLE$ technology as being first applied to mobile communications!

small and low information content instrumentation! and appliance displays.

With the emergence of C; telecommunications! high uality displays will be

critical for handheld devices. PLE$s are ideal for the small display mar"et as

they offer vibrant! full&colour displays in a compact! lightweight and fle%ible

form.

Within the ne%t few years! PLE$s are e%pected to ma"e significant inroads intomar"ets currently dominated by the cathode ray tube and L$ display

technologies! such as televisions and computer monitors. PLE$s are anticipated

as the technology of choice for new products including virtual reality headsets

a wide range of thin! technologies! such as televisions and computer monitors.

PLE$s are anticipated as the technology of choice for new products including

virtual reality headsets a wide range of thin! lightweight! full colour portable

computing communications and information management products and

conformable or fle%ible displays

C9



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CONC(USION

/rganic materials are poised as never before to trans form the world

of display technology.


39/39


RFRNC

WE1 S#TES

www.cdtltd.co.u"

www.research.philips.com

www.covion.com

www.lep&light.com

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Electronics for you :une =77C (88&+7=)

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21199573 Light Emitting Polymer

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