Do you know what OLED is? Recently all of you must have heard about this OLED display because this time, the manufacturer has used OLED display in both iPhone X and Samsung Galaxy Note 8. It is not only providing an excellent look to the phones, but many new features phones are getting from it. Since this OLED display is precious, it is used only in high-end phones and other tech gadgets.
What is OLED?
What is the Full Form of OLED Organic Light-Emitting Diodes (OLED)?
This is a flat light emitting technology. A series of organic thin films are placed between two conductors.
Whenever electric current is passed through them, it emits bright light. OLEDs are emissive displays that do not require a backlight; with this, they are skinny and are much more efficient than LCDs.
OLED Displays are not only thin and efficient, but they also provide the best image quality. With this, they can also be made transparent, flexible, foldable, and rollable, stretchable in the future.
Therefore, it would not be wrong to call OLED the future of display technology. Very little power is required to run it. OLED is currently used in mobile phones, smartphones, and gaming devices.
When did OLED start?
The OLED device was developed in 1987 by Ching W. Tang and Steven Van Slyke in Eastman Kodak. Since then, many changes have been brought to OLED technology, and it has also been improved so that it provides very efficient light using very little power.
What is OLED Technology
OLED panels are made of organic (carbon-based) materials, emitting light only when electricity is passed through them. Because OLEDs have no backlight and filters (such as LCDs), they are more efficient, easier to manufacture, and much thinner – while making them more flexible and rollable.
OLEDs have excellent picture quality – brilliant colors, infinite contrast, fast response rate, and wide viewing angles are some of their main features. OLEDs are also used for OLED lighting, where they can be made thin, efficient, and without any metals.
Working of OLEDs
The main component of the OLED display is the OLED emitter – an organic (carbon-based) material that emits light only when electricity is applied to it.
The basic structure of an OLED is such that an emissive layer is sandwiched between a cathode (which injects electrons) and an anode (which removes electrons).
OLEDs generally work in the same way as conventional diodes and LEDs. Still, instead of using layers of n-type and p-type semiconductors, organic molecules are used to produce electrons and holes.
A simple OLED is made up of six different layers. Its top and bottom have a protective glass or plastic layers. The top layer is called the “seal,” and the bottom layer is called the “substrate.”
Between these layers are a negative terminal (sometimes called the cathode) and a positive terminal (sometimes called the anode). Finally, there are two layers between the anode and the cathode.
Those made up of organic molecules are called the emissive layer (where the light produced is next to the cathode) and the conductive layer (next to the anode).
Many layers are used in modern OLED devices so that they can be made more efficient and durable, but the basic functionality of all of them remains the same.
How OLED Panel is Made
An OLED panel comprises a substrate, backplane (electronics – the driver), front plane, and an encapsulation layer. OLEDs are very sensitive to oxygen and moisture; the encapsulation layer is also critical.
The substrate and backplane of any OLED display are very similar to that of an LCD, but the front plane deposition is unique to OLEDs. There are many ways to deposit and pattern organize layers.
In recent times, almost all OLED displays are made by vacuum evaporation, using Shadow Mask (FMM, Fine Metal Mask) for patterning. This is a straightforward method, but it is very inefficient (many materials get wasted here) because it is challenging to scale up on a large substrate.
Some OLED materials are soluble and deposited using printing methods, where inkjet printing is used. This technology has not yet been commercialized, but OLED makers believe inkjet printing can be scalable, efficient, and cheap to deposit OLEDs.
Why are these OLEDs called organic?
OLEDs are organic because they are made up of carbon and hydrogen. But the truth is that they have no relation with organic food and farming – OLEDs are very efficient, but no harmful metals are used with them – so we can say this is correct. There is a natural green technology in the matter.
How do OLED Lights Emit
- If an OLED is to be lit, we must first attach it to a voltage source applied across the anode and cathode.
- As electricity begins to flow, the cathode receives electrons from the power source, and the anode loses them (or “receives the hole,” if viewed from a different perspective).
- Now we have a situation where the added electrons negatively charge the emissive layer (similar to the n-type layer in a junction diode). Still, the conductive layer becomes positively charged (similar to p-type material, e.g.).
- Positive holes are much more mobile than negative electrons, so they jump quickly across the conductive layer of the boundary to the emissive layer. When a spot (a lack of electron) meets an electron, these two things cancel each other out and release a burst of energy in the form of a particle of light—also called a photon. It occurs.
his process is called recombination because it happens several times in 1-second, so OLED produces continuous light as long as the current continues to flow.
If we want, we can make OLED produce colored light, for which we have to place a colored filter in the glass or plastic top or bottom layer at the bottom of the plastic sandwich.
Suppose we stack thousands of similar red, green, and blue OLEDs side by side and switch them on and off independently. In that case, those pixels will work as in a conventional LCD screen, giving us complex, hi- Can produce resolution colored pictures.
Types of OLEDs
There are two main types of OLED.
1) Traditional OLEDs :
Small organic molecules are deposited on top of the glass to produce light.
2) Light-Emitting Polymers :
These are second-chamber OLEDs that use large plastic molecules called vital polymers. These OLEDs are called light-emitting polymers (LEPs) and are sometimes referred to as polymer LEDs (PLEDs).
Since they are printed over plastic (here, a modified, high-precision version of the inkjet printer is often used) in place of glass, they are thinner and more flexible.
Materials of OLED
By the way, there are many types of OLED Materials. The most basic division occurs within small-molecule OLEDs and large-molecule ones (known as polymer OLEDs, or P-OLEDs).
All the commercial OLEDs that are being used today are SM-OLED based. P-OLEDs were previously well-known because they were naturally processable solutions (and can easily be used in InkJet printing and spin-coating fabrication methods) – but P-OLEDs are no longer popular because of their performance over SM-OLEDs. Not like at all.
Much intensive research is being done to develop more efficient solution-processable SM-OLEDs.
OLED emitter materials can be classified into either fluorescent or phosphorescent. Fluorescent materials can last longer but are not as efficient as bright materials. Right now, most OLED displays use phosphorescent emitter materials – but except for blue, which is still fluorescent, its lifetime is not that great.
Universal Display Corporation is researching PHOLED and has also held its essential patents in this area.
AMOLED vs. PMOLED
These terms are mainly related to the driving method of the OLED display. A PMOLED (Passive-Matrix OLED) is always limited in size and resolution, but they are very cheap and easy to make if we compare with AMOLED (they use Active-Matrix).
An AMOLED always uses an active-matrix TFT array and storage capacitors. If seen, these displays are very efficient and can also be made more prominent, while making them is a challenging task compared to PMOLED.
PMOLED displays are used in small and secondary displays, while AMOLEDs are used in smartphones, tablets, and TVs.
Advantages of OLEDs
OLEDs are superior to their rival LCDs for several reasons. Here I have provided some information about this.
- They are skinny.
- Along with this, they are also lighter and are also very flexible.
- Due to it being brighter, they do not need any backlight.
- They consume much less power than LCD. Due to this, the battery life of portable devices is good by using them.
- Their refresh rate is very high compared to LCD, so you can see fast-moving pictures here in a good way.
- They can produce more accurate colors very well, with excellent viewing angles.
- The cost of making them is also significantly less compared to LCD.
- OLED is available in many different colors, making it very versatile.
- It does not require any warm-up period to start; it starts instantly.
- They are dimmable so that they can also use them for ambient lighting.
- They do not generate heat while burning. Hence they are also called cold lighting sources.
- Their efficiency level is higher than halogen and incandescent lights.
Disadvantages of OLEDs
- Although OLEDs have more advantages, there are also some disadvantages, so let’s know about them.
- They do not last long as the organic molecules in them slowly start degrading.
- Along with this, they are susceptible to water and moisture. Since it is not much applicable to TV sets located in homes, it brings a real challenge to portable devices.
Application of OLEDs
As we know that the technology of OLEDs is very new. They are being used in very few places right now. People are using LCD and LED more, and it has just entered the market. Nevertheless, due to its many good features, it is now being used more.
They are also used mainly in mobile and other electronic gadgets on the display side.
Because their weight is significantly less, it is also foldable; with this, it uses considerably less power, so they are being used in Apple’s Smart Watch.
Big companies like Apple and Samsung have used OLED in their new phones because they not only give an excellent look to the phones but also provide many features.
They are now being used in television because they provide more accurate colors and a wider viewing angle, making the experience very good for the viewers.