LIGHT_EMITTING_POLYMER.ppt

7/29/2019 LIGHT_EMITTING_POLYMER.ppt

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LIGHT EMITTING POLYMER

Presentedby

P.Rajini (09A91A0439)

Under the guidance of

Mr. U.Yedukondalu,M.Tech.,(Ph.D)


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Contents

Introduction

What is LEP?

Chemistry Behind LEP

Structure And Working Types of LEDs

Advantages

Applications Conclusion


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Introduction Rapidly emerging technology for next generation flat

panel displays

Promises thin, light weight emissive displays with lowdrive voltage, low power consumption, high contrast,

wide viewing angle, and fast switching times

Superior than other displays like, LCDs, vacuum

fluorescence displays.


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What is LEP? Polymer that emits light when a voltage is applied to it .

The structure comprises a thin film semi conducting polymer

sandwiched between two electrodes namely anode and

cathode.

The recombination of electrons & holes from the electrodes

leads to emission of light.


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Contd..

The band gap of the semi conducting polymer determines

the wave length (colour of the emitted light).


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Chemistry Behind LEP LEPs are constructed from a special class of polymers

called conjugated polymers.

Plastic materials with metallic and semiconductorcharacteristics are called conjugated polymers.

The charge transport mechanism in conjugated polymers is

different from traditional inorganic semiconductors.


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Structure And Working

The basic LEP consists of a stack of thin organic polymerlayers sandwiched between a transport anode and a metallic

cathode.

The moving holes and electrons from electrodes combine

together to form hole-electron pairs known as excitons.

When this energy drop occurs light comes out from the

device. This phenomenon is called electroluminescence.

The greater the difference in energy drop, the higher the

frequency of the emitted light.


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Structure And Working


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Types of displays

Passive matrix

Active matrix.


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Passive matrix

The current is passed through select pixels by applying avoltage to the drivers attached to the corresponding rows

and columns.

Active matrix

A thin film poly silicon transistor on the substrate address

each pixel individually.

Not limited by current consideration


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TYPES OF LEPs

Flexible organic LEPs

Stacked organic LEPs

Transparent organic LEPs


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ADVANTAGES

Requires only 3.3 volts which is very less.

Greater power efficiency than all other flat panel displays.

No directional or blurring effects.

Fast switching speed, that is 1000 times faster than LCDs.

Roll-up daily refreshable electronic newspapers.


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APPLICATIONS

Multi or full colour cell phone displays

Light weight wrist watches.

High definition televisions.

Automobile light systems without bulbs. Windows/wall/partitions that double as computer screens.


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Conclusion

LEPs are promising, low cost solutions for todaysflat panel displays.

Use full for large area lighting.

Simple to use technology.

Permits flexible lighting and displays.


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Queries?


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Thank you

Documents

LIGHT_EMITTING_POLYMER.ppt