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AMOLED DISPLAY

Introduction

AMOLED display is a display technology for used in mobile devices. AMOLED means Active Matrix Organic light emitting diode Active matrix (AM) OLED displays stack cathode, organic, and anode layers on top of another layer - or substrate - that contains circuitry. A corresponding circuit delivers voltage to the cathode and anode materials, stimulating the middle organic layer.

Two primary TFT back plane technologies, poly-Silicon (poly-Si) and amorphous-Silicon (a-Si) are used today in AMOLEDs.

Important factors of an AMOLED display

• Light Emitting Diode(LED)

• Organic Light Emitting Diode (OLED)

• Pixels

• Thin Film Transistor(TFT)

• Back plane technology

• Active metrix

LED(Light Emitting Diode)

• It is a semiconductor light source

• It indroduced as a practical electronic component in 1962

• Early LEDs are emitted low intensity red light

• Previous years LEDs are mainly used as indicators in many devices

• But modern versions are available across the visible, ultraviolet and infrared wavelengths, with high brightness

• It is used in remote controller of TV and DVDs

• It is also used in various types of display technologies and lamps of vehicles

• When LED is forward biased, electrons are able to recombine with holes within the device

• This recombining process releasing energy in the form of photons

• This effect is called ELECTROLUMINESCENCE

Working of LED

• The color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor

• An LED is often small in area(near than 1mm or 2mm)

• LEDs are integrated with optical components used to shape its radiation pattern

advantages of LEDs

• Lower energy consumption

• Longer life time

• Improved robustness

• Smaller size

• Faster switching

• And durability and switching

OLED(Organic Light Emitting Diode )

• OLED stands for Organic Light Emitting Diode

• The organic in OLED refers to organic material

• There two types of OLEDs are small molecule OLED and polymer OLED

How does OLED work• A layer of organic material is sandwiched

between two conductors(an anode and a cathode),which in turn are sandwiched between a glass top plate (seal) and a glass bottom plate(substrate)

• When electric current applied to the two conductors electrons are able to recombine with holes within the device

• This process produce a bright electroluminescent light directly from the organic material

Schematic of a bilayer OLED: 1. Cathode (−), 2. Emissive Layer, 3. Emission of radiation, 4. Conductive Layer, 5. Anode (+)

Color creation in OLED• OLED has more control over color

expression because it only expresses pure colors when an electric current stimulates the relevant pixels

• The OLED primary color matrix is arranged in red,green and blue pixels which are mounted directly to a printed circuit board

• The thickness of the organic layer is adjusted to produce the strongest light for each of the colors

pixels• Pixels are also known as picture elements

• The pixel is the smallest addressable screen element;

• it is the smallest unit of picture that can be controlled.

• Each pixel has its own address. • The address of a pixel corresponds to its

coordinates.• Pixels are normally arranged in a two

dimensional grid

• and are often represented using dots or squers

TFT(Thin Film Transistor)• TFTs are used as switches to control the

current flowing to each individual pixel typically

•This continues current flow is controlled by at least two TFTs at each pixels

•One to start and stop the the charging of a storage capacitor

•Second to to provide a voltage source at the level needed to create a constant current to the pixels

TFT backplane technology

• For a high resolution display like a TV, a TFT backplane is necessary to drive the pixels correctly.

• TFT backplane technology is crucial in the fabrication of AMOLED displays.

• Two primary TFT back plane technologies, namely polycrystalline silicon and amorphous silicon are used today in AMOLEDs

SUPER AMOLED

• Latest form of AMOLED is the SUPER AMOLED

• super AMOLEDs are 20% brighter

• Have 80% less sunlight reflection

• Have 20% reduced power consumption

Compared with first generation AMOLED technology the claimed advantages of super AMOLED are

ADVANTAGESAMOLED technology has several advantages over conventional displays

•High perceived luminance

•It have better contrast ratio

•Light weight and durable

•Wide viewing angle

•Better brightness

•High color quality and no color shift by viewing angle and/or gray scales.

•AMOLEDs can also have a faster response time than standard LCD screens. Whereas LCD displays are capable of a 1 ms response time or less offering a frame rate of 1,000 Hz or higher, an OLED can theoretically have less than 0.01 ms response time enabling 100,000 Hz refresh rates.

• Lifespan: The biggest technical problem for AMOLEDs was the limited lifetime of the organic materials. In particular, blue AMOLEDs historically have had a lifetime of around 14,000 hours to (five years at 8 hours a day) when used for flat-panel displays. This is lower than the typical lifetime of LCD, PDP technology—each currently rated for about 60,000 hours depending on manufacturer and model.

DISADVANTAGES

•AMOLED displays may be difficult to view in a direct sunlight compared to LCD displays

•The organic materials used in AMOLED displays are prone to degradation

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