Materials Chemistry for Organic Electronics and Photonics

Transcription

1 Materials Chemistry for Organic Electronics and Photonics Prof. Dong-Yu Kim Photonics Polymer Laboratory Dept. of Materials Science and Engineering Gwangju Institute of Science and Technology MSE 701

2 Syllabus : Organic Materials for Organic Electronics and Photonics Weekly Course Schedule Calendar Desciption *Remarks 1st week Introduction of organic electronics and photonics Quiz 50% 2nd week 3rd week 4th week 5th week 6th week 7th week 8th week Fundamentals of organic molecules Organic semiconductors Conjugated polymers Charge transport in organic semiconductors Organic Light-Emitting Diodes : Introduction Organic Light-Emitting Diodes : Hole and electron transporting materials Organic Light-Emitting Diodes : Light emitting materials 9th week Mid-term Exam Mid-termExam 20% 10th week 11th week 12th week 13th week 14th week 15th week Organic photovoltaics : Introduction Organic photovoltaics : Donor and acceptor materials Organic photovoltaics : Interface and electrode materials Organic transistors : Introduction Organic transistors : P-channeland N-channel materials Organic transistors : Gate dielectrics and electrode materials 16th week Final Exam Final Exam 30% 2

3 Introduction of Organic Electronics and Photonics Prof. Dong-Yu Kim Photonics Polymer Laboratory Dept. of Materials Science and Engineering Gwangju Institute of Science and Technology MSE 701

4 The Silicon Age (1947 onwards) IBM Archive 1947 the 1 st transistor (Ge point contact) 1948 the 1 st junction transistor (Ge) John Bardeen Walter Brattain William Shockley (BELL Labs) 4

5 Inorganic Semiconductors The basic ingredient for all high technology devices and products The advantages fast relatively dependable versatile technology is in place they work! The disadvantages costly very difficult to process (UHV equipment and photolithography) some compound SCs have horrible environmental profile (e.g. GaAs) limited stock of some delicate & no mechanical flexibility 5

6 The Soft Age (1977 to.?) A revolution in functional materials for high technology? The 2000 Nobel Prize for Chemistry was awarded for the discovery of metal -like electrical conductivity in iodine-doped polyacetylene Prior to this discovery (Shirakawa, Heeger, MacDairmid), it was thought that organic polymers could not conduct electricity in the solid state The Soft Age was born 6

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9 Organic Materials 9

10 The Soft Age (1977 to.?) Explosion in functional soft-solids research (small molecule and large molecule organic el ectronics) Wild predictions of high tech and low tech applications soft-solid related material benefits plus electrical (semiconducting) functionality IBM, Lucent, Philips, Seiko Epson, HP all have major organic electronics programs 1,888 Transistors! plastic memory smart textiles biosensors electronic ink organic solar cells A thin film conducting polymer transistor and soft-circuitry arrays of these transistors on a flexible polymer sheet Plastic Logic Light emitting polymer displays thin, flexible screens with 180 view 10

11 Printed Electronics Markets Market forecast by component type for 2008 to 2018 in US $ billions, for printed and potentially printed electronics including organic, inorganic and composites Printed electronics will be much bigger than the silicon chip market Source IDTechEx 12

12 Printed Electronics Technology Roadmap Roadmap, Nikkei Electronics, March,

13 Development of Novel Conjugated Polymers 17

14 Organic Polymer-Based LEDs Organic Polymer-Based LEDs from Cambridge Group (1990) PPV derived electroluminescent device that emits yellow-green light " Richard Friend Cavendish laboratory Andrew Holmes Cambridge University, UK Nature1990, 347, MEH-PPV : Soluble PPVs from Santa Barbara (A. J. Heeger) Group (1991) Poly [(2-methoxy-5-(2'-ethyl hexyloxy) -1,4-phenylene) vinylene (2.2 ev) Red shifted from PPV emission soluble because of long side groups; useful for flexible displays 18

15 Light-Emitting Polymers A polymer needs to show fluorescence and to conduct electricity Light Emitting Polymers Convert Electric power into visible light to be a light emitting polymer 19

16 Organic Light-Emitting Diodes (OLEDs) OLED do not have a backlight unlike liquid crystal display (LCD). OLED create light by the following process: A battery or power supply sends a voltage through the OLED. An electrical current flows from the cathode to the organic layer and anode. As explained earlier, the anode removes electrons and adds electron holes in the conductive layer. Between the organic layers is where electrons fill the holes and give off energy in the form of photon light. 14

17 Organic Light-Emitting Diodes (OLEDs) Flexible Display Research Trend 15

18 Flexible Display Applications 16

19 Electrochromic Display 20

20 Electrophoretic Display 21

21 E-Ink Flexible Display 22

22 Solar Cell Light energy (photons) Electrical energy Current (ma) P max I SC Voltage (V) V OC 32

23 The Solar Energy Resource Radiant power at Earth s surface~ TW Electricity consumption ~2 TW ~ 80% from fossil fuels & nuclear, ~0.05% from PV At 10% power conversion efficiency, solar resource can meet de mand with 0.02% of Earth surface area PV is the only technology to convert solar power directly into electricity PV Market Growth Present PV system costs: 7-20 Euro/W p off-grid applications. 4-8 Euro/W p grid-connected. Module 2 4 Euro / W p Aim for: 1-2 Euro/W p for power generation 4-10 Euro/W p for smaller applications. Cost of Si based system falling through economies of scale To accelerate cost reductions, need technological innovations 3.7 GW installed by end

24 Photovoltaic Efficiencies Compared 34

25 Strategies to Cost Reduction Strategies to cost reduction Use less photovoltaic material? Concentration of sunlight Light trapping More work per photon? Multijunction or tandem structures Extracting more work per photon Use cheaper photovoltaic materials and fabrication process? Organic thin film materials Printing Technology Molecular PV materials 35 35

26 Bulk Heterojunction OPVs C 60 CP 36

27 Operation Principle of Fullerene Organic Photovoltaics 37

28 Organic Photovoltaics (OPVs) OPV benefits from the opportunities of renewable energies but offers distinct competitive advantages Pros & Cons of Photovoltaics 38

29 Organic Photovoltaics (OPVs) : Applications 39

30 Module Stack for Organic Photovoltaics (OPVs) Source: Cristophe Brabec Konarka 40

31 Key Challenges for Organic Photovoltaics (OPVs) Current density J Organic solar cell Best h ~4-5% Voltage Electron acceptor Electron donor Maximum ev oc Silicon Best h 24% Irradiance /Wm -2 nm Wavelength / nm 41 41

32 Organic Thin-Film Transistors (OTFTs) Organic transistors are transistors that use organic molecules rather than silicon for their active material. This active material can be composed of a wide variety of molecules. P3HT Advantages compatibility with plastic substances lower temperature manufacturing ( C) lower-cost deposition processes such as spincoating, printing, evaporation less need to worry about dangling bonds makes for simpler processing Disadvantages lower mobility and switching speeds compared to silicon wafers usually do not operate under inversion mode (more on this later) [ Organic FET ] 24

33 Organic Thin-Film Transistors (OTFTs) Applications 25

34 Organic Thin-Film Transistors (OTFTs) Applications 26

35 Printed RFID Tags RFID for Item Level Tagging Organic Thin-Film Transistor (OTFT) Basic Element of Organic Integrated Circuit Inverter P-Channel & N-Channel OTFTs Ring Oscillator 27

36 Materials for OTFTs 1. Conductor (Electrodes) O S O O S O O O S + O S O O n S O n m Colloidal ink of Au Nanoparticles (NP) SO 3 - HSO 3 2. Semiconductor (Active Layers) 3. Insulator (Gate Dielectrics) 28

37 Organic Semiconductors for OTFTs Monocrystalline Polycrystalline Amorphous solids Small molecules (SMs) SMs, polymers polymers pbttt Reproducibility of properties Luminescent property Environmental stability Mechanical stability moderate very high, low very high low moderate high moderate high, moderate high very low low, moderate high Electrical properties (mobility) very good good, moderate moderate to poor 29

38 Organic Semiconductors for OTFTs p-channel μ = cm 2 /Vs n-channel μ = 1-5 cm 2 /Vs cm 2 V -1 S -1 μ = cm 2 /Vs μ = cm 2 /Vs ~ 6 cm 2 V -1 S -1 (in Vacuum) μ = 0.01 cm 2 /Vs μ = 0.6 cm 2 /Vs cm 2 V -1 S -1 (1998, Vacuum Deposition) Relatively low field-effect mobility and air stability compared to p-channel materials μ = 0.1 cm 2 /Vs Significant progress in performance / reliability in recent years, but mobility still limited to cm 2 /Vs. 30

39 Progress in OTFTs Organic semiconductors come in 2 flavors Printed transistor 31

40 Organic Memory : Advantages and Applications Advantages Large area fabrication with extremely low cost Light-weight and flexibility High capacity with bottom-up stacking Capable ubiquitous components that are printed onto plastic, glass or metal foils Technology Performance Evaluation (Polymer Memory) Applications : Inexpensive data storage media : Disposable, mobile, flexible and low-duty applications. Ex.) RFID tag, smart card, e-paper, OLED driving circuit, etc. ITRS 2005 Emerging Research Devices 42

41 Organic Memory: Research Approaches OFET-Type Memory - Ferroelectric polymer insulator - Polarizable gate dielectrics Electrical Bistable Device - Electrical Biatability of Organic Semiconductor layer or Metal Nano-particles, etc. Hybrid Memory - In Combination of Inorganic and Organic Materials AIDCN (2-amino-4, 5- imidazoledicarbonitrile) [R.C.G. Naber, Nature Mater., 2005, 4, 243.] [Y. Yang, Appl. Phys. Lett. 2002, 80, 2997.] [S. Möller, Nature, 2003, 426, 13.] 43

42 Organic Materials to Nanotechnology : Scale without size

43 Organic Materials to Nanotechnology : Graphene Graphite Conductivity: Electrical Resistivity (ohm.m) perpendicular to c-axis parallel to c-axis natural 9.8x x x10-6 Chris Ewels ( Single-layer graphene transistor 45

44 Organic Materials to Nanotechnology : Cabon Nanotube Roll-up of Graphite mesh nanotubes.html 46