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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?:

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 :

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:

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:

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:

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:

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 :

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 :

Disadvantages vulnerable to shorts due to contamination of substrate surface by dust. Voltage drops. Mechanically fragile. Potential not yet realized .

Application :

Application Photovoltaics Polymer semiconductor is used to develop efficient solar cells and light detector. polyLED Philips 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 :


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