Organic light emitting diodes

ORGANIC LIGHT

EMITTING DIODES

B N Manoj10ECE043

INTRODUCTION1)An oled is the light emitting diode in

which electro - luminiscent layer is a thin film of organic compounds, that emits light in response to electric current applied

2)It works on the principle of electroluminiscence

3)No backlighting is required

STRUCTURE :

1)IT CONSISTS OF A CATHODE AND ANODE PLACED ON A SUBSTRATE

2)EMISSIVE LAYER AND CONDUCTIVE LAYER ARE PLACED BETWEEN ANODE AND CATHODE 3)BOTH THE LAYERS ARE MADE OF ORGANIC COMPOUNDS

1) Different colours are produced due to the different types of organic materials used

2) Intensity of the light is controlled by the electric voltage applied to the electrodes

WORKING:

1)Electric current is applied across the electrodes (2-10v)

2)Current flows from cathode to anode

3)Electroluminiscence

occurs at emissive layer

MAKING OF OLED1)Vacuum deposition or vacuum thermal evaporation (VTE):

The vacuum thermal evaporation deposition technique consists in heating until evaporation of the material to be deposited. The material vapor finally condenses in form of thin film on the cold substrate surface and on the vacuum chamber walls

2)Organic vapor phase deposition (OVPD):In a low-pressure, hot-walled reactor chamber, a carrier gas transports evaporated organic molecules onto cooled substrates, where they condense into thin films. Using a carrier gas increases the efficiency and reduces the cost of making OLEDs

3) Inkjet printing:With inkjet technology, OLEDs are sprayed onto substrates just like inks are sprayed onto paper during printing. Inkjet technology greatly reduces the cost of OLED manufacturing and allows OLEDs to be printed onto very large films

INKJET PRINTING1) high-resolution,low cost2) selectively deposit manylayers in a displaySimultaneously3) Surface properties of the substrate affect theuniformity of the filmthickness

Types of oled1)Passive-matrix OLED 2)Active-matrix OLED 3)Transparent OLED 4)Top-emitting OLED 5)Foldable OLED 6)White OLED

ACTIVE MATRIX OLED:

1)In this type of oled,full layers of cathode and anode are presentbetween which organic material is present2)Each pixel is addressed using a thin film transistor ,which is placed over anode,avoiding external circuitory3)When each pixel is put on/off, other pixels can be addressed

PASSIVE MATRIX OLED

1)In this type of oled, anode and cathode are placed perpendicularly, whose intersection forms a pixel2)By using external circuitory,row or coloumn of pixels are addressed3) State of the pixel should be the same until the pixel is addressed again

TOP EMITTING OLED

1)Top-emitting OLEDs have a substrate that is either opaque or reflective.

2)They are best suited to active-matrix design.

TEOLEDImproved active area and power

consumption: Especially advantageous for high-resolution, active-matrix OLED applications, top-emitting structures can increase the effective active area of the display.

With more effective active area, the power required to achieve a specific luminance level can also be reduced.

Use of opaque substrates: By emitting light through the top contact instead of the bottom contact (and substrate), TOLEDs have expanded the variety of substrate materials that can be used

BOTTOM EMISSION OLED

1) Bottom emission oled has a substrate which is transparent.

2) Emission of light is through the apertures of the thin film transistor

STACKED OLED

1) Stacked OLED, in which the red, green,and blue emitters are stacked on top of each other , instead of being placed side-by-side like in other OLEDs, LCDs, and CRTs.

2)As a result, for the same display area as other OLEDs,stacked OLEDs have resolutions three times greater.

3)The stacked OLED displays’ pixels can be scaled verylarge and still look normal.

TRANSPARENT OLED1)Transparent OLEDs have only transparent components (substrate, cathode and anode) and, when turned off, are up to 85 percent as transparent as their substrate.

2)When a transparent OLED display is turned on, it allows light to pass in both directions.

3)A transparent OLED display can be either active- or passive-matrix. This technology can be used for heads-up displays

FOLDABLE OLED1) Foldable OLEDs have

substrates made of very flexible metallic foils or plastics.

2) Foldable OLEDs are very lightweight and durable. Their use in devices such as cell phones and PDAs can reduce breakage, a major cause for return or repair.

3) Potentially, foldable OLED displays can be attached to fabrics to create "smart" clothing

WHITE OLED

1)White OLEDs emit white light that is brighter, more uniform and more energy efficient than that emitted by fluorescent lights. 2)White OLEDs also have the true-color qualities of incandescent lighting.

3)Because OLEDs can be made in large sheets, they can replace fluorescent lights.

ADVANTAGES OF OLED:1)The plastic, organic layers of an OLED are thinner, lighter and more flexible than the crystalline layers in an LED or LCD.

2)OLEDs are brighter than LEDs and LCDs. Because LEDs and LCDs require glass for support, and glass absorbs some light. OLEDs do not require glass.

3)OLEDs do not require backlighting like LCDs. 4) OLEDs can enable a greater artificial contrast ratio (both

dynamic range and static, measured in purely dark conditions)

5)Wider viewing angle: viewing angle compared to LCDs because OLED pixels directly emit light. OLED pixel colours appear correct and unshifted, even as the viewing angle approaches 90° from normal

6)   They have the potential to be able to be produced much more cheaply than conventional LED’s, LCD’s and plasma televisions using processes derived from ink-jet printing

7)   Potential to produce much larger displays compared to LCD and plasma display technology, i.e. a more scalable production process

 8)  Potentially very energy efficient 9)    They can be deposited on large substrates enabling

large areas to be illuminated10)      Lighter than Led 11)    Can produce a true black and infinite contrast ratios

Fast response time: OLEDs can also have a faster response time than standard LCD screens. Whereas LCD displays are capable of between 2 and 16 ms response time offering a refresh rate of 60 to 480 Hz, an OLED can theoretically have less than 0.01 ms response time, enabling up to 100,000 Hz refresh rate.

LCDs work by selectively blocking areas of the backlight to make the images that you see, while OLEDs generate light themselves. Because OLEDs do not require backlighting, they consume much less power than LCDs (most of the LCD power goes to the backlighting). This is especially important for battery-operated devices such as cell phones.

DISADVANTAGES:Cost of production is still high. An OLED screen costs more

than an LCD screen of similar size. This is more an issue for large screen HDTVs than for portable devices that have smaller screens.

OLED screens are difficult to view in bright sunlight as compared to an LCD screen. This is significant in the case of portable electronic devices like a Zune HD or iPod Touch.

Water can easily damage an OLED screen.Life span is another technical problem…for blue led’s,it is

far less than lifespan of lcd’sUV sensitivity: oled’s are senitive to uv rays …to avoid

this ,a protective filter is used to block uv rays

CURRENT APPLICATIONS:

Currently, OLEDs are used in small-screen devices such as cell phones, PDAs and digital cameras.

MAXIMUS OPTIMUS KEYBOARD :

Each of its keys is a display which can dynamically change to adapt to the keyboard layout in use or to show the function of the key.Each key will have an oled screen on it to display

FUTURE APPLICATIONS:

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