When we envision how lighting will look in the future, images of sci-fi movies come to mind — where every car has its own heads-up display, walls and ceilings have seamless illumination, and TVs and even newspapers are fully lit while also being flexible enough to roll up and put in your pocket. If these types of things seem the stuff of fantasy then you may find it surprising to learn that, with OLED technology, these “futuristic” imaginings are not only possible but could be available very soon.
What is OLED?
So, what makes OLEDs special enough to change the future of lighting? Well, Organic Light Emitting Diodes (or OLEDs) stand out from other styles of lights because of their thinness, brightness, flexibility, and transparency. These unique characteristics mean you could have a light that curves to match the architecture of a building, wear clothing with OLED displays, or have a light that serves as a window when not illuminated (just to name a few).
How Does it Work?
An OLED is merely another category of LED light. As discussed in an earlier post, LEDs don’t have a filament and instead create light as electrons flow through a semiconductor material. This semi-conductor consists of two sides — one full of electrons (the n-type) and one with few electrons (the p-type). Where the two sides meet is referred to as the junction, and if you add electricity to the setup, you get what’s known as a junction diode. As the current flows, electrons from the n-type crossover to the p-type, and the empty spaces (or holes) from the p-type move over to the n-type. When the electrons crossover the junction and contact the holes, they release a bit of energy and light. The combined light emitted by the moving electrons produce the brilliant glow of the LED.
OLEDs work the same way as ordinary LEDs except, instead of using the typical n-type and p-type layers, they use organic molecules to generate the electrons and holes. A basic OLED has six layers:
1. Seal – The top layer
2. Cathode – The negative terminal
3. Emissive Layer – Where light is produced
4. Conductive Layer – Gives electrons to the emissive layer
5. Anode – The positive terminal
6. Substrate – The bottom layer
Light in an OLED is created when electricity flows from the cathode to the anode. As this happens, the cathode sends electrons to the emissive layer and the anode takes electrons from the conductive layer. However, as electrons move away from the conductive layer, they leave behind holes which need to be filled with other electrons. So, the holes (which are more mobile than the electrons) jump over to the emissive layer to reconnect with an electron. This crossing over the boundary between the emissive and conductive layers is very similar to what happens when electrons pass over the junction in standard LEDs, and like in an LED, this movement makes a photon of light. As long as the electricity flows, this process will repeat over and over, keeping the OLED illuminated.
Types of OLEDs
While there are multiple types of OLEDs, the two most prominent kinds are passive matrix OLEDs (PMOLEDs) and active matrix OLEDs (AMOLEDs). The main difference between these two styles is the way the anodes and cathodes are arranged. For example, on PMOLEDs, the anodes and cathodes are in strips and layered perpendicular to each other, whereas on an AMOLED there are full layers of both cathodes and anodes, and there is a thin film transistor (TFT) below the anodes. The TFT acts as the circuitry that controls which pixels get turned on.
Both PMOLEDs and AMOLEDs have their advantages:
Benefits of PMOLEDs:
- Easier to make
- Work well with small screens (ideal for cell phones, MP3 players, other small devices)
Benefits of AMOLEDs:
- Uses less power
- Refresh faster
- Work well with large screens (ideal for computer monitors, TVs, electronic signs and billboards)
Pros and Cons of OLEDs
OLEDs have the potential to change the way we view television, light our homes, view our gadgets, and much more. Still, the technology is evolving and it isn’t without its shortcomings. Consider these pros and cons:
Pros of OLEDs
- Ultra-thin – Requires no backlight like LCDs and other displays
- Extremely light
- Flexible – Consists of organic, plastic layers
- Bright – Due to multi-layered conductive and emissive layers as well as the lack of light-absorbing glass
- Energy efficient – Consume less power than LCDs
- Refreshes quickly -Up to 200 times faster than LCDs
- Truer colors than LCDs
- Transparent
- Easy to produce
Cons of OLEDs
- Shorter life – Displays don’t last as long as LCDs or traditional LEDs
- Expensive – The manufacturing process is still very costly
- Susceptible to water – Easily damaged from water (could be an issue with cell phones)
Applications as Light Source
Although OLEDs are currently making big waves in the electronics industry, their ability to produce white light means they also have the potential to bring all sorts of new lights to our homes and workspaces. We envision ceilings adorned with bright, flexible lights that are as artistic as they are functional. It truly opens up a whole new world of interior lighting design, as OLEDs can be integrated into everything from wallpaper to windows. Not to mention their energy efficiency makes them an environmentally friendly choice.
Most major lighting companies are getting involved in OLED technology, but there are mixed feelings on the long term potential of OLED. Continue to follow our blog to see how this unique lighting solution evolves.