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

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

Introduction 3

Applications OLED_EarlyProduct.JPG mages/1107/14/sony_xel2-thumb- 450x337.jpg projects.com/euprojects/olla/downloads/pi ctures/olla_4generations.jpg 4

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

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

How OLEDs Work Organic Semiconductivity SMALL MOLECULE TYPEPOLYMER TYPE Aluminum oxinate Polyphenylene vinylene 7

How OLEDs Work Structure Electrons (-) Electron-holes (+) 8

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

Configuration  Substrate  Glass, PET  Anode  ITO, Polyaniline  Cathode  Ca, Mg-Ag, Al-Li  HTL  ETL 10 Anode Substrate HTL Cathode EMLETL

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

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

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

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

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

Fabrication Techniques: Organic Vapour Phase Deposition 16

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

Market 18

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

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

Questions? Thank you