A Future Technology

OLED stands for Organic Light Emitting Diode. It can be called as ‘organic cousins’ of LEDs. As the name suggests, the word “organic” signifies the presence of organic emissive layer sandwiched between the cathode and the anode.

Types of OLEDs:

1: Small Molecule OLED

2: Polymer OLED

Lighting applications that use LEDs and OLEDs, or light emitting polymers are commonly referred to as solid-state lighting (SSL). In OLED, whole solid surface acts as the light source.

The basic OLED cell structure consists of a stack of thin organic layers sandwiched between a transparent anode and a metallic cathode, which are in turn sandwiched between a glass top plate (seal) and a glass bottom plate (substrate) . The organic layers comprise a hole-injection layer, a hole-transport layer, an emissive layer and an electron-transport layer.

This can be understood by these figures:

When a voltage is applied to the electrodes the charges start moving in the device under the influence of the electric field.

Electrons leave the cathode and holes move from the anode in opposite direction. The recombination of this charges leads to the creation of a photon with a frequency given by the energy gap (E = hν) between the LUMO(Lowest unoccupied Molecular Orbital) and HOMO(Highest Occupied Molecular Orbital) levels of the emitting molecules.

Therefore, the electrical power applied to the electrodes is transformed into light.

In short, when electric current is applied to the two conductors, a bright, electro-luminescent light is produced directly from organic material.

Different materials and dopants can be used to generate different colours and the combination of them allows building up a white light source. Here is the Figure:

Like their LED counterparts, OLEDs produce light by therecombination of electrons and holes. In the case of the OLED,when a voltage is applied across the device, electrons areinjected at the cathode and provide electrons to the emissivelayer(s). The conductive layer provides electrons to the anode,leaving “holes” within the layer. These holes migrate to theemissive layer where they recombine with the excess electrons.As the electrons drop into the holes, they release energy in theform of light. The color of the light emitted depends on thecomposition of the organic emissive layer. Multiple layers (forexample red, green and blue) can be combined in one device toproduce any desired color including white.

Displays:• The famous AMOLED (Active Matrix OLED) display

used in smart phones (mainly Samsung and HTC).

• PMOLED(Passive Matrix OLED) displays are used in mp3 players or secondary displays on cell phones.

• Transparent Displays: Samsung unveiled their new development in International Consumer Electronic Show 2010, the Transparent OLED Laptop. This is the world’s first largest transparent OLED prototype. People took great interest in this development for its unique and stylish transparent look. Here are some pictures of this Laptop:

• Flexible Displays: Using OLEDs, it is also

possible to create Flexible Displays:

•Sony showed off a full-screen laptop (pictured

below), bendable e-reader, and Walkman bracelet

concepts, all based around flexible

OLED technology and built with "flexible

bioplastics," along with the flexible display that

going to power them all when they hit the

market...

Organic LEDs aren't just limited to screens:

They're also used for general illumination since they're energy efficient, more so than many of today's other light sources. They can also illuminate large areas. One application could entail using transparent sheets to turn windows into lamps at night. Already, OLEDs are used for backlighting small LCD screens.

OLEDs in Future Cars:

Smart Dashboard Displays;

Windshields transparent OLEDs;

Internal and External Lighting;

Back window alerts and messaging.

OLED can also be used to treat skin cancer and acne. A UK team is developing wearable OLED stickers that will cure skin ailments on the go. Many skin cancers are currently treated by a combo of light and drugs (called photodynamic therapy) but current light sources are large and the therapy requires lengthy hospital visits. Lumicure Ltd. is looking to use OLED in the treatment instead. The OLEDs would be attached to sticking plaster that can be placed on the diseased skin. Not only will it be comfortable, the patient could possibly do the therapy from home. Named: OLED bandage.

Being self-luminous, they require no backlighting. By contrast, LCDs require either an external light source (reflective type) or a fluorescent or LED backlight. No backlighting means OLED displays are smaller in size, use less power, weigh less and cost less.

In summary, OLED displays have:

High brightness and contrast

Ultra-wide viewing angle

No backlight required

Thin, compact form factor

Fast response time and higher refresh rate

Low power consumption

OLED displays can be made very thin, making them very attractive for televisions and computer monitor applications.

Colour capability: It is possible to fabricate Flexible: It is possible to make OLED displays flexible by using the right materials and processes.

Very thin: OLED displays that can generate all colours.

Power consumption: The power consumed by an OLED display is generally less than that of an LCD when including the backlight required. This is only true for backgrounds that are dark, or partially dark.

Bright images: OLED displays can provide a higher contrast ratio than that obtainable with an LCD.

Wide viewing angle: With many displays, the colourbecomes distorted and the image less saturated as the viewing angle increases. Colours displayed by OLEDs appear correct, even up to viewing angles approaching 90°.

Fast response time: As LCDs depend upon charges being held in the individual pixels, they can have a slow response time. OLEDs are very much faster. A typical OLED can have a response time of less than 0.01ms.

The First OLED TV. . .

Sony Bravia XEL-1 is the world’s first OLED TV that is only 3mm thick. It

features 960×540 resolution, 1,000,000:1 contrast ratio, 16:9 aspect ratio

and support for Dolby Digital. Sony’s unique Super Top Emission technology

intensifies brightness and efficiency.

What’s great about Sony Bravia XEL-1 is that it only consumes up to 40

percent less power than a conventional 20 inch LCD panels. Another great

feature includes the Screen Tilt Feature, it allows you to tilt it up to 70

degree to accommodate different viewing positions.

Sony XEL-1 OLED TV is priced at $2,499.99.

Moreover, OLEDs are also used in wrist watches, headsets, remote controls, display of audio systems, digital photoframesand many other kind of electronic devices.

Kodak was the first to release a digital camera LS633 with an OLED display in March,2003.

Moreover, the companies Huawei, LG, Sensics Natalia, Lenovo, Olympus, Panasonic and many more have also contributed towards it.

Water can easily damage an OLED screen. They are highly moisture sensitive.

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.

In summary, OLED is the screen technology of the future. As manufacturing processes improve and production cost becomes cheaper more and more LCD displays with be replaced with OLED displays.

www.google.com

www.fadooengineers.com

www.Radio-electronics.com

www.oled-display.net

http://www.televisions.com/tv-articles/OLED-Technology-Explained/Advantages-and-Disadvantages.php

www.oledinfo.com

http://en.wikipedia.org/wiki/Oled

www.howstuffworks.com

www.cancer.gov

Electronics for you: jan 2012 issue

http://www.radio-electronics.com/info/data/semicond/leds-light-emitting-diodes/organic-oled-basics-tutorial.php

Prof. Anurag Kandya

Prof. Chanakya Bhatt

Prof. Neha Patni

Prof. Kapil Narayanan

PREPARED BY:

vivek brahmbhatt

(11BEE006)

& dhruvin patel

(11BEE021)