OLED, or Organic Light-Emitting Diode, is the latest technology to take storm in the world of electronic displays. Some of you are probably wondering, what is an OLED? OLEDs are small carbon-based organic molecules that emit light when exposed to an electrical current. This light can be used to create a display on a TV, cell phone, hand held gaming device, and just about anything else.
How it works:
An OLED usually consists of five parts, which are: substrate, anode, cathode, conducting layer, and emissive layer. The substrate, which is usually made of plastic or glass, is used to contain the OLED. An anode is placed on top, and is used to remove electrons. Next, a conductive layer and an emissive layer are added, which make up the organic portion of the OLED. The conductive layer is an organic plastic material, such as polyaniline or polyacetylene that loses electrons to the anode, thus leaving "electron holes" and giving it a negative charge. The emissive layer (another plastic, such as polyfluorene), receives electrons from the cathode, giving it a negative charge. The electron holes and electrons attract and recombine, and energy is released by electrons from the emissive layer in the form of light. The color of the light released is dependent on the type of emissive layer.
Sony 11" OLED Model XEL-1
Applying this process to a screen
On an OLED display, each pixel's brightness is controlled by the amount of current applied. OLEDs are configured into passive matrix or active-matrix form, similar to LCDs.
Passive-matrix OLEDs (PMOLED) are used on small screens, such as on cell phones and MP3 players. Sony recently announced its Walkman X at CES 2010, which will use a PMOLED.
Active matrix OLEDs (AMOLED) are more suitable for larger displays such as a TV, as they do not need to power external circuitry, making them more efficient the PMOLEDs. Some companies, such as Samsung, have began used AMOLEDs on cell phones.
High contrast ratio
OLEDs are significantly brighter than LEDs, which makes them capable of achieving much higher contrast ratios.
OLEDs make their own light, so unlike conventional LCDs, no backlighting source is needed. This allows manufacturers to make extremely small screens. In 2008, Samsung created an OLED display with a thickness only 0.05mm. That's thinner than a sheet of paper! This display is also bendable as well.
Short life span
The biggest issue with OLEDs is their limited lifespan, particularly for blue OLEDs. Red and green OLEDs have been able to operate properly, with tested lifetimes from 46,000 to 230,000 hours (HowStuffWorks), but blue OLEDs have been limited to only 14,000 hours. This life expectancy is sure to increase however, as the technology progresses.
OLEDs are still quite new to the display market, and as with most new technology, they are quite expensive to produce. For example, Sony's first publicly sold OLED HDTV, the XEL-1 retails for $2499. With only an 11-inch screen, it's not exactly a bargain. Expect these prices to drop as OLED becomes more popular and other manufacturers begin to produce OLED TVs.