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Minlu Zhang

Minlu Zhang. Outline. Small molecular OLEDs (OLED) Polymer OLEDs (PLED) Applications Challenges. Single layer device. Cathode. P-n junction device. Organic Layer. Multiple layers device. Anode. Cathode. Cathode. Substrate. Electron transport layer. Electron Injection layer.

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Minlu Zhang

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  1. Minlu Zhang

  2. Outline • Small molecular OLEDs (OLED) • Polymer OLEDs (PLED) • Applications • Challenges

  3. Single layer device Cathode P-n junction device Organic Layer Multiple layers device Anode Cathode Cathode Substrate Electron transport layer Electron Injection layer Hole transport layer Electron transport layer Anode Emissive layer Substrate Hole transport layer Hole Injection layer Anode Substrate Small molecular OLEDs — Structure

  4. Cathode Electron Injection layer Electron transport layer Emissive layer Transparent substrate ITO HIL HTL EML e- ETL EIL Cathode Hole transport layer e- e- Hole Injection layer Anode Substrate h+ h+ h+ Small molecular OLEDs — Device operation principle • Electrons injected from cathode • Holes injected from anode • Transport and radiative recombination of electron hole pairs at emissive layer LUMO — Ec Light HOMO — Ev

  5. Small molecular OLEDs — Materials EIL, ETL: n-type materials Alq3, PBD PBD Alq3 HIL, HTL: p-type materials NPB, TPD NPB TPB EML: Fluorescent dye DCM2 Phosphorescent dye PtOEP, Ir(ppy)3 DCM2

  6. Small molecular OLEDs — Electrodes 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

  7. Substrate Vacuum Cathode Small molecules Electron transport layer Hole transport layer Anode Substrate Heater Small molecular OLEDs — Device preparation Thermal vacuum evaporation Growth: ~10-5-10-7 Torr Room temperature ~20 Å- 2000 Å

  8. Cathode Cathode Emissive polymer Emissive polymer Anode Conducting polymer Substrate Anode Substrate Polymer OLEDs— Structure and Operation http://www.ewh.ieee.org/soc/cpmt/presentations/cpmt0401a.pdf

  9. Polymer OLEDs— Materials Conducting polymers: PANI:PSS PDOT:PSS PANI PSS PDOT Emissive polymers: R-PPV PFO

  10. Spin coating Polymer film Substrate Ink jet printing Substrate Polymer OLEDs— Fabrication Spin coating Ink jet printing Screen printing Web coating

  11. 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

  12. 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

  13. Samsung large OLED displays KODAK OLED displays http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=1473/1481/1491&pq-locale=en_US Applications — Full color OLED display

  14. White OLEDs From Universal Display Corporation http://www.universaldisplay.com/white.htm Applications — Solid state white lighting

  15. Challenges • Lifetime • Red >10,000 hrs • Green >10,000 hrs • Blue ~1,000hrs ? • High efficiency ? • Pure color?

  16. Thank You!

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