1. Organic Light Emitting Diodes (OLED) July 2011

2. Organic Light Emitting Diodes
Solid State Semiconductor
100 to 500 nanometers thick
Emits light when electricity is applied
Suitable for small displays, TVs, and thin area (panel) lighting

3. How OLEDs Work
Electrical current is applied and electrons travel from the cathode to the emissive layer to the conductive layer to the anode
The removed electrons leave “holes” and the traveling electrons find them
Once the vacancy is filled the electron falls into an energy level of the atom that has the “hole”
By falling into the energy level the electron gives up energy in the form of a photon
This process releases visible light

4. Changing Parameters
Intensity (Brightness): Dependent on Current, more current equals brighter light. Not dependent on voltage
Color Saturation, Lifetime, and Efficiency: Dependent on the number of layers, typically ranging from 2 to 5
Efficiency: Doping with organometallic materials improves efficiency

5. OLED Schematic
Cathode injects electrons, emissive layers gives off photon anode removes electron when electrical current is supplied

6. Example of OLED Cell Material

7. Commonly Used Polymers
Polymers used in PLED's must be:
Electrically conductive
Highly photoluminescence efficient
Conjugated polymers are good energy producers due to the energy gap between pi bonding states
Polycarbazole and PFO (poly (9,9-dialkyfluorene) are commonly used
PEDOT:PSS is a good hole transporting polymer, but more research needs to be done to find a better one

8. Different Types of OLEDs
Molecular Categories
Small Molecule (SMOLED)
Weigh less than 1000g/mol
Used in evaporation deposition methods
Much more advanced- Used in all OLED products
More efficient than PLED due to deposition techniques
Polymer (PLED)
Large molecule OLED
Weigh more than 1000 g/mol
Able to be put into a solution
Used in spin coating and inkjet printing deposition methods
More research is needed but they are capable of being used in more flexible, lower voltage applications, which makes them candidates for larger displays

9. Most Popular Designs Top Emitting OLED Bottom Emitting OLED
Transparent Cathode / Reflective Anode
Most Efficient
Larger aperture ratio results in higher resolution
Bottom Emitting OLED
Reflective Cathode / Transparent Anode
Light reflected through glass substrate
Transparent OLED
Both Cathode and Anode are transparent
Light emitted in both directions

10. Diagrams of Transparent and Top Emitting OLED's

11. Different Formations AMOLED Active Matrix OLED
Made by layering different layers of the cell
Has a thin film transistor which the anode overlays
The thin film transistor determines which pixels get turned on and off to form an image
Pro: Uses less power than passive matrix OLED
Most commonly used in larger displays
Computer Monitors, Flat-Screen TV's, Electronic Billboards

12. Different Formations PMOLED Passive Matrix OLED
Constructed of strips of the different layers
Anode strips arranged perpendicular to cathode strips
Intersection of cathode and anode make pixels, which is where light is emitted
External power source used to determine which pixels get turned on and off
Pro: Easy to make Con: Consumer more power
Used most commonly is small screens (3in diagonal)

13. Diagram of Passive and Active Matrix OLED's

14. Stacked OLEDs
Red, Green and Blue layers stacked on top of each other, opposed to side by side
Creates smaller pixel size
Higher resolution
All three colors together make white light
All connected together requires color filter
Less efficient because 50% of light lost in filter

15. True Stacked OLEDs Still stacked on one another
Each color is connected separately to the electrical source
Allows for no color filter to be needed
More efficient
Used in larger pixel devices

16. Other Types of OLEDS Foldable OLED White OLED
Made of very flexible foils or plastics
Lightweight and durable
Used in cell phones and PDA's to reduce breakage
Future uses include integration into fabrics to make clothes that have a cell phone, GPS and computer chip integrated into them
White OLED
Emits white light that is brighter than fluorescent bulbs
Have the benefit of true color qualities like incandescent bulbs
Can be manufactured into large sheets for home and business uses
Have the ability to reduce energy costs

17. Manufacturing OLEDs

18. Backplane Switching and driving circuitry
OLEDs require thin film transistor (TFT)
Must be strong and stable, more so than in a LCD TFT
Common TFT Material
Amorphous Silicon
Low Temperature Polysilicon (LTPS) (AMOLED)
Oxide TFT, Super Grain Silicon, InGaZnOx

19. Depositing and Patterning
Vacuum Evaporation (VTE)
Deposition method used to manufacture all OLEDs on the market today
Molecules are heated, evaporated and then condensed on a cool substrate
Shadow mask used to make pixels
Very expensive and inefficient
Difficult to scale to production level
Difficult to scale up because the metal mask is very delicate and with size it becomes susceptible to bending and breaking

20. Depositing and Patterning
Organic Vapor Phase Deposition (OVPD)
Uses low pressure and high temperatures
In a chamber, a carrier gas moves evaporated material to cooled substrate
Not used in mass production
More efficient and precise than VTE

21. Depositing and Patterning
Laser Annealing
Laser used to pattern organic material
First film is made by VTE, then the film is placed on a substrate
Laser used to heat material and transfer film to substrate
Laser Induced Thermal Imaging
Much more accurate than VTE
Achieves higher pixel density and easier to scale

22. Depositing and Patterning
Inkjet Printing
Inkjet used to spray solution processable OLED material onto substrate
Fast, efficient and scalable compared to other methods
Disadvantage: Creating a reliable and efficient solution processable OLED
Commonly used with PLEDs but can be used with SMOLED
Solution processable OLED material does not have as long of a life span as OLED material that can be evaporated and applied onto a substrate.

23. Other Deposition Techniques
Dupont
Developed spray printing process
Uses nozzles for continuous spray
Nozzles move at 4-5 m/sec
Less efficient display than other techniques but could result in a cheaper display than an LCD
Can print a 50” OLED TV in less than 2 minutes
Other Methods
Roll to Roll
Spin Coating

24. Encapsulation OLEDs are very sensitive to moisture and oxygen
Must be protected by shield or barrier
Barrier must be cheap, flexible, and not labor intensive
Permanently bonded with epoxy or resin
Must be chemically, water, heat and solvent resistant
Classic barrier used is glass, but is bulky and heavy
Metal is a good barrier, but it is not transparent
New materials being used include plastics and nanomaterials

25. Advantages of OLEDs
Power Consumption: No backlighting required, more efficient than LCD
Lighting: More aesthetic properties than other forms of light, does not require shades
Environment: Do not contain any heavy, toxic metals
Materials: Very simple structure compared to LCD
Transportation: Very light, less gas needed and pollution due to transporting materials
Lifetime: Potential to have long life, not attainable right now
Size: Much thinner than other technologies and much brighter
View: Large field of view (170 degrees)

26. Disadvantages of OLEDs
Lifetime: Currently very undependable
Blue lifetime much shorter than other materials
Solution: Use red and green phosphorescent materials and blue fluorescent material (Short Term Fix)
Scaling: Not easy to go to production due to issues with the backplane and deposition/patterning phases
Lighting: Inorganic OLEDs will always be more efficient
Direct Sunlight: Can not see OLED in sunlight
Production: Very wasteful, overspray and energy efficiency

27. Displays Currently range from 0.66” to 5.5” on regular market
Super expensive commercial displays up to 17”
Set backs: Blue fluorescent lifetime, scaling to production, and deposition techniques
Future: Economically feasible, more efficient displays, larger in size

28. Lighting Currently only in small quantities and on the luxury market
Not as efficient as LCDs, but more aesthetically pleasing
Lamp sells for 25,000€
Future: Hope to get cheaper and be mass produced
Need to work on efficiency

29. OLED Market 4 major areas
Chemicals/Materials
Deposition
Encapsulation
Manufacturing Equipment
Total Market in 2009 was estimated to be $ 1billion
Total Sales of AMOLED and PMOLED $800million

30. Top Companies Samsung $566 Million in Revenue
RiTDisplay $106 Million in Revenue
Pioneer $60 Million
TDK $42 Million
Visionox $15 Million
Others: Sony, Philips, Fraunhofer, Lumiotec, OSRAM, Vitex, SNU Precision, AUO

31. Market: Past, Present, Future
2009: PMOLED Sales $300 Million, AMOLED Sales $500 Million
OLED: Currently $1 Billion market
2015: $1.4 Billion OLED Materials
2015: $1.8 Billion OLED TVs
2015: $500 Million Transparent Conductors
2018: $6 Billion Lighting
Substrate and Encapsulation 20% of total cost

32. Where Does Sono-Tek Fit In?
Spray solution processable OLED material
Reduce waste and overspray
Increase process efficiency
Films have very high uniformity increasing their efficiency and durability
Lower consumer cost, more economically feasible
Lower capital cost compared to other deposition techniques
ExactaCoat: R&D and Small Batch Processes
FlexiCoat: R&D and small scale production

33. Any Questions?