Lecture 10

• 1. Lecture #10Organic Field Effect Transistor(OFET)Department of Instrumentation & Control Engineering, MIT, Manipal1

2. Department of Instrumentation & Control Engineering, MIT, ManipalContents1. Introduction2. Why Organic?3. Organic vs Inorganic4. Device operation5. Characteristic of OFETs6. Organic Molecule Pentacene7. More about OTFT2 3. Introduction3 Bardeen, Shockley, and Brattain invented the world's firsttransistor in 1947 The first OFET was reported in 1986. It was based on a film of electrochemically grownpolythiophene. Four years later, the first OFET employing a small conjugatedmolecule was fabricated.S.Meenatchisundaram, Department of Instrumentation & Control Engineering, MIT, Manipal 4. Why Organic?4 Organic electronics are lighter, more flexible, and lessexpensive than their inorganic counterparts. They are also biodegradable (being made from carbon). This opens the door to many exciting and advanced newapplications that would be impossible using copper or silicon. However, conductive polymers have high resistance andtherefore are not good conductors of electricity. In many cases they also have shorter lifetimes and are muchmore dependant on stable environment conditions thaninorganic electronics would be.S.Meenatchisundaram, Department of Instrumentation & Control Engineering, MIT, Manipal 5. Organic vs Inorganic5 Organic electronics, or plastic electronics, is the branch ofelectronics that deals with conductive polymers, which arecarbon based. Inorganic electronics, on the other hand, relies on inorganicconductors like copper or silicon.Silicon Sample Carbon SampleS.Meenatchisundaram, Department of Instrumentation & Control Engineering, MIT, Manipal 6. Organic vs SiliconS.Meenatchisundaram, Department of Instrumentation & Control Engineering, MIT, Manipal 6 7. Advantages of Organic7 Organic electronics are lighter, more flexible Low-Cost Electronics No vacuum processing No lithography (printing) Low-cost substrates (plastic, paper, even cloth) Direct integration on package (lower insertion costs)S.Meenatchisundaram, Department of Instrumentation & Control Engineering, MIT, Manipal 8. Disadvantages of Organic8 Conductive polymers have high resistance and therefore arenot good conductors of electricity. Because of poor electronic behavior (lower mobility), theyhave much smaller bandwidths. Shorter lifetimes and are much more dependant on stableenvironment conditions than inorganic electronics would be.S.Meenatchisundaram, Department of Instrumentation & Control Engineering, MIT, Manipal 9. Device operation9 OFETs are composed of three terminals1. source2. drain3. Gate And a semiconductor layer and an insulating layer between thesemiconductor and gate.S.Meenatchisundaram, Department of Instrumentation & Control Engineering, MIT, Manipal 10. Device operationS.Meenatchisundaram, Department of Instrumentation & Control Engineering, MIT, Manipal 10 11. Device operation There are two common device configurations used in OFETs1. Top ContactWhen the source and drain electrodes are evaporated onthe top of the organic material.2. Bottom ContactWhen the source and drain electrodes are evaporated onthe dielectric before depositing the organic semiconductor.Top Contact Bottom ContactS.Meenatchisundaram, Department of Instrumentation & Control Engineering, MIT, Manipal 11 12. Characteristic of OFETs12Applied voltage to the gate induces an electric field through thedielectric and causes the formation of an accumulation layer ofcharges at the interface of the semiconductor deposited.OFET characteristic can be classified as:a. Transfer Characteristicb. Output Characteristic These characteristic depends on whether Vgs is varied whileVds is kept constant, or Vds is varied while Vgs is keptconstant.S.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 13. Characteristic of OFETsS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 13 14. Characteristic of OFETsS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 14 15. Characteristic of OFETsS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 15 16. Characteristic of OFETsS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 16 17. Organic Molecule - PentacenePentacene Molecule: Organic semiconductor Composed of five Benzene rings Polycyclic Aromatic hydrocarbon Easy to synthesize High carrier mobilityS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 17 18. OFET Merits and DemeritsAdvantage DisadvantageCost effective Thermal stabilityLarge Selection of Material Chemical Stability (Oxidation)Lighter and flexibleS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 18 19. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 19 20. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 20 21. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 21 22. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 22 23. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 23 24. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 24 25. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 25 26. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 26 27. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 27 28. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 28 29. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 29 30. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 30 31. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 31 32. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 32 33. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 33 34. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 34 35. More about OTFTS.Meenatchisundaram, Department of InstrumentationControl Engineering, MIT, Manipal 35