Paper-thin Displays

OLED technology can be used to make thin, versatile, and low-power displays with clear, high-contrast images

Fold your computer’s screen, carry it in your pocket, and when you’re ready to use it, take it out, unfold it, put it up on your computer, and use it as you would your conventional screen. Cool? If a promising display technology–OLED (Organic Light Emitting Diode)–takes off, you may soon be able to do just this.

OLED displays, named after the technology, are made up of self-luminous organic materials that glow when voltage passes through them. This means that they do not need backlighting (usually by bulky mercury lamps), making them slimmer, lighter, and consumers of lesser power (only 2 to 10 volts) than the current ubiquitous LCDs (Liquid Crystal Displays), nearly half of whose power supply is for backlighting. This also opens up the potential to create thin and versatile displays.Also known as OED (Organic Electroluminescent Display), OLEDs have a wide viewing angle (up to 160 degrees) and display clear, high-contrast images, even in bright light. 

Unlike many of the other technologies we are discussing here, OLEDs are already in use, albeit in limited areas. OLEDs are currently finding use in car stereos (Pioneer) and cellphones (Motorola). However, for larger displays like laptops and desktops, OLEDs are unlikely to replace LCDs in the next few years; during which time they will probably coexist. This is because unless they begin to be mass produced, OLEDs will remain fairly costly, and it takes time to iron out the glitches of any new technology.

Meanwhile, LCD manufacturers, sensing competition ahead, are pulling up their socks and are working to improve the display’s brightness, viewing angles, and reduce its power consumption. Moreover, at 5,000 operating hours, the life spans of OLEDs are much shorter than those of LCDs, which often last about 10,000 to 15,000 hours. Meanwhile, watch out for OLEDs in more car radios, cellphones, digital cameras, camcorders, pagers, and
handhelds. 

How they work

So how do OLEDs work and what is their physical composition? In between a transparent anode and a metallic cathode lie multiple layers of thin substrate, which include a hole-injection layer, a hole-transport layer, an emissive layer, and an electron-transport layer. When voltage is applied to this device, the positive and negative charges recombine to emit photons. The emissive layer is also ‘doped’ with fluorescent molecules to enhance
electroluminescense.

Types of OLEDs

Work is on to develop three types of OLED products: TOLED (Transparent OLED), FOLED (Flexible OLED), and SOLED (Stacked
OLED).

TOLEDs are made up of transparent components that can emit light in one or both directions, and can be used in aircraft and car windshields for overlaying navigation systems, fabricating windows for home entertainment or teleconferencing, or cellphones for clearer display in daylight.

FOLEDs are built on flexible substrates that can be folded, bent or rolled to adopt any shape, enabling integration with almost any surface.

SOLEDs have three layers of stacked TOLEDs (red, green, blue) instead of them being next to each other as in LCDs and CRTs. This translates into full color quality and a resolution that is nearly three times higher than that of normal displays.

Juhi Bhambal