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Acknowledgement
To Mr. Tashi (Lecturer in the department of ECE) To Mr. Manoj Sharma (Lecturer in the department of Electrical Engineering) To Mr. Phurpa Gyeltshen (BE4E) To all my Friends
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Outline
Introduction Definition Brief History OLED structure How OLED emits light Operation principle Types of OLEDs Advantages and Disadvantages Why OLED..Not LCD Applications of OLED Conclusion
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Introduction
Organic materials are of great interest for electronics applications OLED consists of organic layer between two electrodes OLEDs can replace the current technology in many applications due to following performance advantages over LCDs Greater brightness Faster response time for full motion video Fuller viewing angles Lighter weight More power efficiency
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What is an OLED?
An OLED is an electronic device made by placing a series of organic thin films between two conductors
When electrical current is applied, a bright light is emitted A device that is 100 to 500 nanometers thick or about 200 times smaller than a human hair
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History of OLED
1950s First observation of electroluminescence in organic materials by Bernanose and co-workers at the Nancy University, France. 1960s AC driven electroluminescent cell was developed. 1965 electroluminescence by recombination of electrons and holes without applied source. 1987 Chin Tang and Van Slyke introduced first light emitting diode from thin organic layers. 1990 electroluminescence in polymers was developed
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The OLED Structure
Substrate : supports OLED
Anode :gives electron holes to conductive layer Cathode :gives electrons to emissive layer Organic Layer: conductive and emissive layers
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How OLEDs Emit Light
The battery or power supply applies a voltage
Electrical current flows from the cathode to the anode
At the boundary between the emissive and the conductive layers, electrons find holes The OLED emits light
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Operation Principle
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Operation Principle (cont)
Voltage is applied across the OLED Anode is positive with respect to the cathode Current flow through the device from cathode to anode Cathode gives electrons to the emissive layer Anode gives electron holes to the conductive layer Emissive layer becomes negatively charged Conductive layer becomes rich in positively charged holes Recombination of electron hole pairs at the emissive polymer.
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Types of OLEDs
Passive-matrix
Active-matrix
Transparent
Top-emitting
Flexible White
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Passive Matrix
Organic layer between anode and cathode that run perpendicularly Intersections forms the pixels where light is emitted Easy to make Use more power Best for small screens
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Active Matrix
Full layers of cathode, organic molecules and anode Anode over lays a thin film transistor(TFT) that form matrix Requires less power Suitable for large screens
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Transparent
Contains transparent components only When turned off, 85 percent transparent as their substrate When turned on, allows light to pass in both directions can be either active- or passive-matrix used for heads-up displays
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Top-Emitting
Have opaque or reflective substrate
Best suited to active-matrix design
Use in SMART CARDS
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Flexible
Substrate made of flexible metallic foils or plastics Lightweight and durable Their use in devices such as cell phones can reduce breakage
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White
Emit white light that is brighter, more uniform & more energy efficient than that emitted by fluorescent lights Have the true-colour qualities of incandescent lighting Reduce energy costs for lighting
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Advantages and Disadvantages
Advantages
Thinner, lighter and more flexible
Brighter Consume much less power
Disadvantages
Short lifetime UV Sensitivity Sunlight effect
Easier to produce and make into larger sizes Highly water prone Large field of view
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Manufacturing
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Better contrast ration
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Bendable OLED Display
OLED technology is threatening LCD standard because of its flexibility, low power consumption and versatility
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Applications of OLED
TVs Cell phone screens Computer screens Lights Portable device displays
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OLED as a light source
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Current OLEDs
OLED Televisions OLED Digital cameras
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Future Uses for OLED
Lighting Flexible/bendable lighting Wall paper lighting defining new ways to light a space Cell phones Nokia 888
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Conclusion
OLED lights have a growing popularity in display solutions OLEDs are a more and more commonly used display Has the potential to be the next generation of displays and lighting No doubt that their presence in the market will continue to increase Viewing angle is always an issue in flat screens OLEDs will remain the technology of choice
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References
http://expertscolumn.com/content/oled-advantages-and-disadvantages
http://www.verbatimlighting.eu/en_1/led-article-velve-oled-technology_6280.html
http://www.ledke.com/news/How-OLED-Working-principle.html http://electronics.howstuffworks.com/oled.htm http://www.pacificdisplay.com/lcd_oper_basics.htm http://www.ehow.com/list_5780762_disadvantages-lcd-flat-panelmonitors.html http://electronics.howstuffworks.com/oled1.htm http://electronics.howstuffworks.com/oled2.htm http://electronics.howstuffworks.com/oled3.htm http://www.ledke.com/news/OLED-Advantages-Disadvantages.html http://electronics.howstuffworks.com/oled5.htm http://electronics.howstuffworks.com/oled6.htm http://electronics.howstuffworks.com/oled.htm
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Thank you!!!
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