LIGHT EMITTING POLYMER

SUBMITTED BYMustahid Ali

INDEX INTRODUCTION WHAT IS LEP?

Construction Ink Jet Printing Active and passive matrix Basic principle and technology Light emission

ADVANTAGES DISADVATAGES APPLICATIONS CONCLUSION REFERENCES THANKS.

INTRODUCTION In 1990, LEP was born at

Cambridge University UK by researchers.

Full color LEP driven displays are efficient brighter and easier to manufacture.

What is LEP?

It is a polymer which emits light when voltage is applied to it.

Thin film of semiconducting polymer sandwiched

between two electrodes.

Cont…..

Recombination of the electrons and holes leads to the emission of light.

Band gap determines the color of light emitted.

Construction

Indium-tin oxide used for anode and aluminum and calcium for cathode.

Single-layered device work only under forward biased DC.

Cont…..

symmetrically configured works under AC as well as DC(reversed and forward)

Spin coating machine is used for manufacturing

Ink jet printing Red, green and blue polymers are

jetted into well defined areas.

Flim thickness has to be uniform to display uniform emission.

Active and passive matrix

Color display are formed by positioning matrix of red, green and blue pixels.

To control the pixels passive and active drivers are used.

Cont… Active display have transducers and

in passive matrix each row and each column has its own driver.

Passive display are prone to flickering but they are used where cheap and simple displays are required.

Basic principle and technology

Single C-C bond consist of two electrons shared in overlapping wave functions.

Spherical s-orbital and p-orbital form four equal unsymmetrical ,tetrahedral, oriented hybridized sp^3 orbital.

Cont…. A band formed by overlap of these

hybridized orbitals from two carbon atom is referred to as sigma bond.

Conjugated pi-bond refers to a carbon ring whose bond alternate between single and double bond.

Light emission Electroluminescence is process in

which electromagnetic radiation is emitted from material when electric current is passed through it.

Conduction in polymer is not same as in metals.

Advantages

Require only 3.3 volts and have lifetime of more than 30,000 hours.

Low power consumption. Self luminous. No viewing angle dependence. Display fast moving images with optimum

clarity. Cost much less to manufacture and to run

than CRTs because the active material is plastic.

Can be scaled to any dimension.

Cont….. Fast switching speeds that are typical of

LEDs. No environmental draw backs. No power in take when switched off. All colors of the visible spectrum are

possible by appropriate choose of polymers. Simple to use technology than conventional

solid state LEDs and lasers. Very slim flat panel.

Disadvantages vulnerable to shorts due to

contamination of substrate surface by dust.

Voltage drops.

Mechanically fragile.

Potential not yet realized.

Application

PhotovoltaicsPolymer semiconductor is used to

develop efficient solar cells and light detector.

polyLEDPhilips will demonstrate its first

polyLED based prototype based on organic light emitting diode technology.

Cont…. Baby phone

Uses the light emitting diode to respond the baby’s activity.

Mp3 display player

Conclusions Organic material are being used to

transform the display technology. Using light emitting diodes organic

full color displays may replace LEDs in laptop and even desktop computers.

Such display can be deposited on flexible coils eliminating fragile and heavy glass substrates used in LCDs.

First products using organic display is already in market.

References

www.cdtltd.co.uk

www.research.philips.com

www.covion.com

IEEE JOURNAL

THANKS