How OLED display screens work


What is OLED

When we covered what is OLED and what it means, we described what OLED stands for. We need to understand what what OLED are before we dig into how OLED display screens work.  LED stands for light-emitting diodes.  Diodes are electric components that are classified as passive. Their function is to allow current to follow in one direction while preventing it to flow to another direction. However, OLEDs are special types of diodes that are made to serve both as a light source and as a diode. Today, they have found special uses because they do not consume a lot of power light many other power sources.

So now what is OLED? They are LEDs where the light is not emitted by the normal aluminium gallium nitride but uses organic molecules to emit light. So when you term organic, understand that it means items that are produced in an environmentally friendly many. However, in this case, it means compounds made of carbon atoms.

LEDs are more energy-efficient compared to other light sources such as incandescent lamps. So, no energy is lost in form of heat. Old lamps heats filaments which become white-hot and then light is emitted. You should know that the LED produces light by having electrons that go through solid materials.

History of OLED

We cannot exhaust this topic on how OLED display screens work if we do not look into the history of the OLED.


How ordinary LED works

Since we can comfortably call an OLED and advanced LED, let us discuss how the LED works so that we can under the OLED better. The process starts with two semi-conductor materials. The two materials are such that more contains more electrons while the other has more holes (or positive charges). So, when the two materials are brought together, they create a “neutral” point. So at the junction is a region is created that is empty. When the power is connected to the two semiconductors, the electrons will jump through the junction. So LED has three regions, the n region, p region, and the neutral region; in other words three layers.

How OLED display screens work
The three regions of a diode

In short, it works in a similar manner as a normal diode, the only difference is that LED  will emit light.

How OLED  works

So, instead of the semiconductors, OLED uses organic molecules to produce the light. Instead of three layers, OLED has 6  regions as shown in the image below.

How OLED display screens work

Protective layers of glass are found on the top and bottom of the rest of the layers and are called seal and substrate respectively. Below the top layer ( or the seal) is the cathode ( also known as the negative terminal). You guessed correctly; the anode layer is just above the substrate. The Anode layer is also called the positive terminal. Between the anode and cathode are two more layers called the conductive layer and emissive layer. The conductive layer is adjacent to the anode layer while the emissive layer is adjacent to the cathode layer.

So how is light produced then?

The process starts with the application of a voltage across the two terminals. The conductive layer becomes more positively charged and the emissive layer becomes more negatively charged.  So, the positive charges flow or jump into the negatively charged emissive layer.  When the electrons (or negative charges) meet with the protons (or positive charge) they cancel each other. During the neutralization process, there is a lot but brief energy that is released. This energy is referred to as a photon. Since there are many electrons and protons canceling each other, energy is released as a continuous stream of protons and hence the light we see. This process where electrons and protons cancel each other’s is called recombination.

I know you might also want to understand how our OLEDs can produce different colors such as red, green, yellow among others. To produce any light color you wish, a colored filter is added below the seals and above the substrate. If you create a group of red, blue, and green OLED, you get a pixel when controlled independently. This is how OLED display screens work.

Types of OLEDs

Two types of OLED, small organic molecules and the polymer OLED.  The polymers are also called light-emitting polymers (LEPs).  The light-emitting polymers are flexible since they are thinner.  This is not the only use of LEP, they are also able to convert light into electricity.  When used to produce electricity, they are referred to as polymer solar cells.

Polymer solar cells

There so many ways to design the OLED. If you may have noticed there are those made such that light emerges at the top of the seal. Sometimes, light is made to pass through the substrate at the bottom. When creating a pixel,  OLEDs are arranged side by side.  Where high-density pixels ( more pixels per centimeter) OLED  are stack on top of one another.

How OLED display screens work
A polymer solar cell
Advantages of OLED

OLED can offer to higher contrast ratio than that offered by the LCDs. They are also lighter and more flexible.


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