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Lecture 7 oms


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  • 1. Lecture VII. Applications Electrostatic Imaging and Xerographic materials Organic Light-emitting diodes ) OLEDS and Active Matrix OLEDS (AMOLEDS) for Display and Lighting Solar Cells Field-effect transistors Batteries Photo-detectors Luminescence for Land-mine Sniffing Lasers Switches E-Ink
  • 2. Inorganic Vs. Organic Material Properties
  • 3. Limitations At Early Stage  Organic materials have often proved to be unstable.  Making reliable electrical contacts to organic thin films is difficult.  When exposed to air, water, or ultraviolet light, their electronic properties can degrade rapidly.  The low carrier mobilities characteristic of organic materials obviates their use in high- frequency (greater than 10 MHz) applications. These shortcomings are compounded by the difficulty of both purifying and doping the materials.
  • 4. Electrostatic Imaging
  • 5. Chester Carlson History of Xerography The first xerographic image 10-22-1938, Astoria, NY. slide #2
  • 6. History of Xerography 1906: Haloid Corp. founded 1900 1910 1920 1930 1940 1950 1938: 1st xerographic image 1949: 1st copier - Model A 1950 1960 1970 1980 1990 2000 1959: Xerox 914, 1st plain paper automatic copier - 7 1/2 copies/min 1964: LDX (long distance xerography) - 1st fax 1973: Xerox 6500 - 1st color copier 1977: Xerox 9700 - 1st laser printer 1988: Xerox 5090 - 135 copies/min 1997: Docutech digital printer (180 copies/min) 1997: Docucolor 70 - 70 color prints/min Today Xerox has 91,400 employees (50,200 in US) and $18.2 billion in revenues
  • 7. What is Xerography? Creation of a visible image using surface charge pattern on a “photoconductor”. Visible images consist of fine charged particles called toners”. slide #5 Xero-graphy = Dry-Writing (Greek)
  • 8. Xerographic Prints are composed of toners 5-10 microns COLORDigital prints are halftones
  • 9. Inside a xerographic printer Photoreceptor
  • 10. Charging Subsystem (Corotron): Electrons Positive Ions Free ions are attracted to wire; Free electrons are repelled. Counter-charges build up on grounded surfaces. Rapidly moving electrons and ions collide with air molecules, ionizing them and creating a corona. Electrons continue to follow Electric Field lines to Photoreceptor until uniform charge builds up HV Power Supply (-) HV Power Supply (-) HV Power Supply (-) slide #10
  • 11. Transfer to paper • Electric field moves particles from photoreceptor to paper or transparency • Detachment field must overcome toner adhesion to photoreceptor Apply E Field Paper Paper Photoreceptor Photoreceptor slide #18
  • 12. Additives control adhesion Changing type type of additive modifies adhesion Atomic Force Microscopy results
  • 13. Electrical Field Detachment of Fine Particles E. Eklund, W. Wayman, L. Brillson, D. Hays, 1994 IS&T Proc., 10th Int. Cong. on Non-Impact Printing, 142-146 slide #19 Measure Many Particle Adhesion Donor Receiver V transparent conductive electrodes VV
  • 14. Fusing Subsystem • Permanently affix the image to the final substrate – paper of various roughness – transparency (plastic) • Apply heat and/or pressure Hot Roll Fuser: Pressure Roll Heat Roll Paper slide #21
  • 15. Cleaning and Erase Subsystems • Removes unwanted residual toner and charge from photoreceptor before next imaging cycle – Physical agitation removes toner (blade or brush) – Light neutralizes charge by making entire photoreceptor conductive slide #22
  • 16. Physics of the Photo-discharge of the Corona Charge
  • 17. Future of Xerography • Color: Wide gamut, offset quality • High Image Quality: High resolution, continuous tone • High Speed: Full color at 200 pages per min, and higher • Higher reliability: No paper jams • Lower cost: Xerography vs. inkjet slide #25
  • 18. Reference The physics of XEROGRAPHY: Howard Mizes Xerox Corporation Wilson Center for Research & Technology Webster, New York
  • 19. Organic Light-emitting diodes (OLEDS) and Active Matrix OLEDS (AMOLEDS) for Display and Lighting
  • 20. Overview
  • 21. Inorganic LED’s
  • 22. Inorganic Vs. Organic LEDs
  • 23. Why Organic LED?  Vibrant colors  High contrast  Wide viewing angles from all directions  Low power consumption  Low operating voltages  Wide operating temperature range  A thin and lightweight form factor  Cost-effective manufacturability , etc
  • 24. Organic LED Energy Diagram
  • 25. A full color, 13-inch diagonal small-molecular-weight OLED display with 2mm thickness. Flexible internet display screen S. R. Forrest in Nature428, 911 (2004) Applications — Full color OLED display
  • 26. Samsung large OLED displays KODAK OLED displays Applications — Full color OLED display
  • 27. OLED Device Physics and Chemistry
  • 28. EIL, ETL: n-type materials Alq3, PBD HIL, HTL: p-type materials NPB, TPD EML: Fluorescent dye DCM2 Phosphorescent dye PtOEP, Ir(ppy)3 Small molecular OLEDs — Materials Alq3 PBD NPB TPB DCM2
  • 29. Cathode Organic Layer Anode Substrate Single layer device Small molecular OLEDs — Structure Cathode Hole transport layer Anode Substrate Electron transport layer P-n junction device Electron transport layer Hole transport layer Anode Substrate Emissive layer Electron Injection layer Cathode Hole Injection layer Multiple layers device
  • 30. Electron transport layer Hole transport layer Anode Substrate Emissive layer Electron Injection layer Cathode Hole Injection layer HOMO — Ev LUMO — Ec Transparent substrate ITO HIL HTL EML ETL EIL Cathode h+ e- h+ h+ e- e-Light  Electrons injected from cathode  Holes injected from anode  Transport and radiative recombination of electron hole pairs at emissive layer Small molecular OLEDs — Device operation principle
  • 31. Anode: Indium-tin-oxide (ITO): 4.5-5.1 eV Au: 5.1 eV Pt: 5.7 eV Cathode: Ca: 2.9 eV Mg: 3.7 eV Al: 4.3 eV Ag: 4.3 eV Mg : Al alloys Ca : Al Alloys Small molecular OLEDs — Electrodes
  • 32. Substrate Small molecules Vacuum Heater Cathode Hole transport layer Anode Substrate Electron transport layer Small molecular OLEDs — Device preparation Growth: ~10-5-10-7 Torr Room temperature ~20 Å- 2000 Å Thermal vacuum evaporation
  • 33. Polymeric OLEDS
  • 34. Cathode Emissive polymer Anode Substrate Cathode Conducting polymer Anode Substrate Emissive polymer Polymer OLEDs — Structure and Operation
  • 35. Conducting polymers: PANI:PSS PDOT:PSS Emissive polymers: R-PPV PFO Polymer OLEDs — Materials PANI PDOT PSS
  • 36. Polymer OLEDs — Fabrication Spin coating Ink jet printing Screen printing Web coating Substrate Ink jet printing Substrate Polymer film Spin coating
  • 37. Organic Solar Cells
  • 38. Example
  • 39. Self-Organized Discotic Liquid Crystals for High-Efficiency Organic Photovoltaics
  • 40. Organic Field Effect transistors
  • 41. Organic Thin Film Transistors (OTFTs) Organic material Organic material
  • 42. An Example of an I-V of OTFTs Lg = 20 µm W = 220 µm 400 nm SiO2 50 nm organic
  • 43. Battery Applications
  • 44. Li LiI PVP-I CT complex Li+
  • 45. Photo-detectors
  • 46. Luminescence for Mine-Sniffing
  • 47. Organic Semiconducting Lasers
  • 48. Organic Switches
  • 49. E-ink