materyaller oled
TRANSCRIPT
Luminescent Materials:
Phosphors and Organic LEDs
Prof. Michael J. SailorDepartment of Chemistry and Biochemistry
University of California, San Diego
Outline
I. Luminescence in Nature-Bioluminescence-Green Fluorescent Protein
II. Organic Light-Emitting Diodes
III. Phosphors- Fluorescent Lighting- Luminescent Silicate Polymers
IV. Electoluminescent Porous Silicon
Mosquito Bay, Puerto Rico
This unique bay contains up to 720,000 non-toxic dinoflagellates per gallon of bay water.Each flash a strobe of bluish light whenagitated at night and can create enough light toread a book from.
Bacterial luciferin
Dinoflagellate luciferin has a structure similar to chlorophyll
Vargulin is found “seed shrimp"
Coelenterazine is the most common marine luciferins
LuciferinO2
Oxyluciferin +
LIGHTLuciferase
ATP
Chemistry of Bioluminescence
•Two chemicals are required for luminescence•The light-producing compound is called a luciferin•The catalyst is called a luciferase
•Energy, here shown as ATP, must be provided to resetthe systemTypical Luciferin Molecules
Green Fluorescent Protein (GFP)
- A naturally fluorescent material that occurs in a jellyfish in the Puget Sound.- Here the DNA code for this protein
has been injected into bacteria which then makes GFP.
- The bacteria is then grown on an agar plate, and exposed to blue light.
Dr. Brian Reid, Yale School of Medicine.
top view
Green FluorescentProtein
the protein’s beta-sheets protect the chromophore from being quenched.
side view
inside, three aminoacids (serine, tyrosine, andglycine) are cyclized andoxidized to form the chromophore.
•Thin, and daylight-viewable•Rugged, yet lightweight•Power efficient•Easily custom formatted
OLEDs are of Interest to Industryand Academia because of their
Properties and Versatility
Professor Mark E.Thompson- USC
Electron transport layer
Hole transport layer
Cathode
Transparent Anode
Basic Organic Light EmittingDiode (OLED) Design
•A thin sandwich of one or more specialty polymers between twoelectrodes
•One electrode must be transparent to let the light out
•A battery voltage across the electrodes generates holes andelectrons in the respective layers which upon recombination emitenergy in the form of light.
•The color (energy) of the light depends upon the choice ofpolymer and can be tuned using well-defined organic syntheticmethods
The Appeal of Plastic Displays
FLEXIBLEFLEXIBLEADVANTAGE: Durable displays can be fashioned on novelsubstrates, including plastic, instead of glass.
DREAM PRODUCTS:•Cloth-like screens that roll up like scrolls, reducing the sizeof laptop computers.•Luminescent strips could also be sewn into clothing fordecoration or advertising.
THIN AND INEXPENSIVETHIN AND INEXPENSIVEADVANTAGE: Produced in fewer layers than LCDs, with fewermanufacturing steps. Don't need backlights.
DREAM PRODUCTS:•Devices will be very light and cheap, paving the way forvideo ''postcards'' that could record and display five-secondvideos.
SCALABLE PICTURE ELEMENTSSCALABLE PICTURE ELEMENTS
ADVANTAGE: Pixels--dots of colored light--are deposited invariable sizes and shapes.
DREAM PRODUCTS:•Giant video screens applied like wallpaper to living roomwalls.•Aircraft makers could replace heavy ceiling lights with onelong ceiling panel.
Fluorescent Lighting
Cross-section
glass
phosphors
plasma
- The plasma generates UV light, mercury vapor is the most efficient, but xenon is safer.
- White light is generated from red, green, and blueemitting phosphors that often contain Europium,
Cadmium, Lead, or Terbium activator metalsthat are toxic and/or expensive.
Ballast (current control, etc.)
A. L. Srivastava and T. J. Sommerer, Interface, Vol. 7, No. 2, (1998), 28-31.
Emission Spectrum of a typical cool, white halophosphate phosphor
(a) red emitting V2O3:Eu3+
(b) green emitting LaPO4:Ce3+, Tb3+
(c) blue emitting (Sr, Ca, Ba)5(PO4)3Cl:Eu2+
Emission Spectrum of a rare-earth phosphorused in the triphosphor blend.
A. L. Srivastava and T. J. Sommerer, Interface, vol. 7, No. 2, (1998), 28-31.
Luminescent Silicone Polymers
R Acid Luminescence*-H formic vs, pale yellow-CH3 acetic s, deep orange-CH(OH)CH3 lactic s, orange-CF3 trifluoroacetic m, deep red-m-C6H4-OH salicilic s, yellow
* Green et al, Science, 247, (1997) 1826.
(EtO)3Si(CH2)3NH2 + RCOH
=O
Si- O)3 - Si(CH2)3NHC-R + H2O + EtOH=
O(
amide
Organic Light-Emitting Diodes
“Electroluminescent Properties of Self-Assembled Polymer Thin Films.”Jing Tian, Chung-Chih Wu, Mark E.Thompson, James C. Sturm, Richard A.Register, Advanced Materials, 1995, 7,395-398.
Photo courtesy Kathleen R. Gisser, TimothyJ. Hughes, Kodak