AMOLED & LED - A Dive in

My friends got thier new mobiles this week, a Samsung NOTE 2, a Samsung S 3. 

The attractive one of both is its display. A word AMOLED fell in my ears. What ? AMOLED ?

I remember LED, a light emitting diode. But AMOLED, is a type of LED?

Yes, AMOLED is a type of LED. It is an Active-Matrix Organic LED.

LED, to understand it you should remember you physical terms from your school days. Like cathode, anode, p-type, n-type semiconductor. These are not engineering terms, but simple school physical terms.

A LED, as it name implies its a DIODE.A diode is the simplest sort of semiconductor device. 

Broadly speaking, a semiconductor is a material with a varying ability to conduct electrical current. We are not going more than that to avoid confusion.

A LED has 2 parts, a P-Type semiconductor (positively charged HOLES) and a N-Type Semiconductor (Negatively charged ELECTRONS).

You guys remember a LED have 2 pins, a long and a short one and we use a AA(battery we use for wall clock) to make a LED glow. Positive side should be connected to long one and respective other. On the reverse LED will not glow.

The logic simple, when battery is connected. the electrons will be attracted towards holes, once they combines(electrons + holes) in the junction electrons will release energy in the form of PHOTONS (which is a light energy).

Light energy may be visible/invisible depending upon  the semiconductor we use. E.g TV Remote - An infrared LED which generates invisible photons. Other colour LED are visible to human eye.

OLED
Organic light emitting diode. OLED's are invented for making flexible and thin displays. With LED we cannot make a flexible because of its crystalline in nature. As we discussed earlier a LED P & N type semiconductors are used between anode & cathode.

But, OLED has a different construction process. Instead of P&N semiconductors, organic polymers layers are used. 2 or 3 layers of polymers will be used.

1st layer will be a conductive layer, connected with anode to transport holes (+vely charged).

2nd layer is an emmisive layer, connected with cathode to transport electrons (-vely charged).

When electrons combines with holes, light will be generated.




AMOLED
We are not going to talk about construction anymore. AMOLED stands for Active-matrix OLED. 

Active-matrix technique deals with addressing and arrangement of OLED's in a display.
In a single AMOLED, different colour layers forms a matrix. The different colour layers, say RED, BLUE, GREEN will be in single OLED. Respective colours are chosen at display time.


Why AMOLED not LCD ?

AMOLED has faster refresh time,
Consumes less power,
Flexible,
Light weight.

The above are significant things AMOLED has when compared to LCD. That's how flexible displays are possible now.

Thanks for the amazing technology.

Related interesting topics,

1. Pentile matrix, a sub pixel technique used in AMOLED screens.