1. O RGANIC L IGHT E MITTING D IODES Andrew Sanders, Fawzi Salama, John P. Handrigan 12/02/2010

2. Outline  Introduction  How OLEDs work?  Materials  Fabrication Techniques  Recent Developments  Conclusions 2

3. Introduction 3

4. Applications http://en.wikipedia.org/wiki/File: OLED_EarlyProduct.JPG http://www.newlaunches.com/entry_i mages/1107/14/sony_xel2-thumb- 450x337.jpg http://www.hitech- projects.com/euprojects/olla/downloads/pi ctures/olla_4generations.jpg 4

5. Advantages  Low power consumption  Flexible displays (with polymer layer)  High Contrast (1,000,000:1)  Thin Displays (3mm)  Thin organic Layer (100 -150 nm) 5

6. History  Commercialization of inorganic LEDs in 1960’s  OLEDs using small molecules  Tang and Van Sylke from Kodak (1987)  Discovery of electroluminescence from polymers  J. H. Burroughes et al. (1990) at University of Cambridge 6

7. How OLEDs Work Organic Semiconductivity SMALL MOLECULE TYPEPOLYMER TYPE Aluminum oxinate Polyphenylene vinylene http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=24868131http://upload.wikimedia.org/wikipedia/commons/9/94/Polyphenylene_vinylene.png 7

8. How OLEDs Work Structure Electrons (-) Electron-holes (+) http://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=19353440 8

9. HOMO (valence band) Electron Holes (+) Electrons (-) Emissive Layer Δ E=h/ ( λ c) LUMO (Conduction band) 9 How OLEDs Work Electroluminescence

10. Configuration  Substrate  Glass, PET  Anode  ITO, Polyaniline  Cathode  Ca, Mg-Ag, Al-Li  HTL  ETL 10 http://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=19353440 Anode Substrate HTL Cathode EMLETL

11. EML Materials 11  Properties  Semi-conductor  Radiative recombination dominates due to large energy level  3 basic colors  2 types Small Molecules Polymers

12. Photo Emitting Materials  Small Molecules  Green: Alq3  Blue: Distyrylarylenes  Red: Rubrene  Polymers  Green: PPV  Blue: PPP’s, PFO’s  Red: PT’s, P3ATs 12 Rubrene Alq3 Distyrylarylene PPV PPPPT

13. Fabrication Techniques 13  Wet Techniques  Inkjet Printing  Dry Technique  Vacuum Thermal Evaporation  Organic Vapour Phase Deposition

14. Fabrication Techniques: Inkjet Printing 14  Advantages  Solution for large area deposition  Disadvantages  Deposited film is non- uniform

15. Fabrication Techniques: Vacuum Thermal Evaporation 15  Advantages  High film uniformity  Vacuum equipment is available  Disadvantages  Organic build up on chamber walls  Expensive

16. Fabrication Techniques: Organic Vapour Phase Deposition 16

17. Fabrication Techniques: Organic Vapour Phase Deposition 17  Advantages  High uniformity  Reduced organic material consumption  Does not require high-vacuum conditions  Disadvantages  Expensive equipment

18. Market 18

19. Current Research  Phosphorescent materials  Device lifetime  Application to solar cells 19

20. Conclusions  Young technology  Enormous progress on materials and fabrication techniques  Growing technology for electronics display  With lower costs, the best technology to adopt 20

21. Questions? Thank you