SLIDES ON BASIC STRUCTURE AND FUNCTIONING OF POLYMER DIODES

1. POLYMER DIODES

2. POLYMER LED’S
 SOME POLYMERS CONDUCT ELECTRICITY
AND EMIT LIGHT
 THESE SEMICONDUCTING POLYMERSARE
NOW EXTENSIVELY USED IN MARKETS

3. STRUCTURE
 CONSISTINGOF A SERIES OF LAYERS-
ELECTRODES,ACTIVE SEMICONDUCTOR
MATERIAL, INSULATORSAND SO ON
 AND IT IS ATTRACTIVE IFTHEY CAN BE
ASSEMBLED,AS POLYMERS CAN BE

4. BONDING FEATURES
 ALTERNATE SINGLE AND
DOUBLE CARBON –
CARBON BONDS
 MATERIALS ARE SAIDTO
BE CONJUGATED
 C=C FORMED WHENTWO
OFTHREE 2P ORBITALS
ON EACH CARBON ATOM
COMBINEWITH 2S
ORBITALS FORMING SP2
HYBRID
 FORMATION OFTHREE
SIGMA MOLECULAR
ORBITALSTAKE PLACE
 THIRD P ORBITAL FORMS
A PAIR OF π MOLECULAR
ORBITALSTHAT ARE
SPREAD OUT IR
DELOCALIZED OV ER A
POLYMER CHAIN
 THE LOWER π-BONDING
FORMSVALENCE BAND
WHILETHE
ANTIBONDING FORMS
THE CONDUCTION BAND.

5. BONDING BASICS
THIS ‘BANDGAP’ GIVESTHE POLYMER SEMICONDUCTING NATURE

6. STRUCTURE

7. CONTD..
 MOST CONJUGATED POLYMERS HAVEA
SEMICONDUCTOR BAND GAPS OF 1.5-3eV.
 WELL SUITED FOR OPTOELECTRONIC
DEVICES.

8. MOST WIDELY USED POLYMER
 PPV- POLY PHENYLENEVINYLENE HAVING
A BAMD GAP OF 2.5eV EMITSYELLOW
GREEN LIGHT
 IT IS MADE UP OF BENZENE RINGS –
PHENYLENE UNITS- LINKEDTO ONE
ANOTHERVIATWO CARBONS,WHICH ARE
ALSO BOUNDEDTO A SINGLE HYDROGEN
ATOM.

9. THE PHENYLENE VINYLENE UNIT

10. PLED STRUCTURES
 FIRST ITWAS MADE USING ATHIN LAYER
OF POLYMER SANDWICHED BETWEENA
PAIR OF ELECTRODES
 NEGATIVE ELECTRODE INJECTS
ELECTRONS INTOMPOSITIVER FILM
 POSITIVE ELECTRODES INJECTS HOLES

11. CONTINUED..
 AN ELECTRONAND HOLE CAPTURE ONE
ANOTHERWITHINTHE POLYMER AND
THEY FORMA NEUTRAL ‘ÉXCITON’
 IT IS A BOUND EXCITED STATETHAT CAN
DECAY BY EMITTING A PHOTON
 THE PROCESS IS KNOWN AS
ELECTROLUMINESCENCE SINCE EMISSION
IS CAUSED BY ELECTRIC FIELD BETWEEN
THE ELECTRODES.

12. CONTD..
 NEGATIVE ELECTRODE SHOULD HAVE
LOWWORK FUNCTION SOTHAT
ELECTRONS CAN BE EASILY INJECTED
 POSITIVE ELECTRODE SHOULD HAVE HIGH
WORK FUNCTIONTO SUCK IN ELECTRONS
FROMTHE POLYMER
 HOLE INJECTING ELECTRODE- MADE OF
INIDIUM-TIN OXIDE.

13. PEDOT /PSS LAYER
 EXTRA LAYERWHICH IMPROVESTHE
INJECTION OF HOLES
 PEDOT- POLY (ETHYLENEDIOXY)
THIOPHENE
 IT IS MIXEDWITH POLSTYRENE
SULPHONICACID (PSS)TO FORMA STABLE
AND HIGHLY CONDUCTINGCHARGE
TRANSFER PLEX
 IT IS DEPOSITEDON AQUEOUS SOLUTION
TO FORMA LAYER ON INIDIUMTIN OXIDE

14. PEDOT-PSS LAYERING

15. USES OF POLYMER LED’S
 BACK LIGHTS FOR MOBILE PHONES
 PORTABLE ELECTRONIC PRODUCTS
 GRAPHIC DISPLAYS-TELEVISION SCREENS,
COMPUTER MONITORS, PALMTOP
DEVICES
 LAB-ON-A CHIP DEVICE COULD BE USED IN
HOSPITALS
 DIRECT PRINTING- INK JET PRINTING
 OLED’S

16. USES
 PORTABLE ELECTRONIC PRODUCTS

17. USES
 GRAPHIC DISPLAYS-TELEVISION SCREENS,
COMPUTER MONITORS, PALMTOP
DEVICES

18. USES
 DIRECT PRINTING- INK JET PRINTING

19. USES
 OLED- ORGANIC LIGHT EMITTING DIODES

20. DISPLAY SYSTEMS OF PLED

21. CONCLUSION
PLED’SARE OF IMMENSE IMPORTANCEANDTHEIR USAGE CARRIESA
SIGNIFICANCE IN PRESENT DAYTECHNOLOGICALADVANCEMENTS.

22. THANK YOU