An organic light-emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compounds which emit light in response to an electric current. This layer of organic semiconductor material is situated between two electrodes. Generally, at least one of these electrodes is transparent.
OLEDs are used in television set screens, computer monitors, small, portable system screens such as mobile phones and PDAs,watches, advertising, information, and indication. OLEDs are also used in large-area light-emitting elements for general illumination. Due to their low thermal conductivity, they typically emit less light per area than inorganic LEDs.
An OLED display works without a backlight. Thus, it can display deep black levels and can be thinner and lighter than liquid crystal displays. In low ambient light conditions such as dark rooms, an OLED screen can achieve a higher contrast ratio than an LCD—whether the LCD uses either cold cathode fluorescent lamps or the more recently developed LED backlight.
There are two main families of OLEDs: those based on small molecules and those employing polymers. Adding mobile ions to an OLED creates a Light-emitting Electrochemical Cell or LEC, which has a slightly different mode of operation.
OLED displays can use either passive-matrix (PMOLED) or active-matrix addressing schemes. Active-matrix OLEDs (AMOLED) require a thin-film transistor backplane to switch each individual pixel on or off, but allow for higher resolution and larger display sizes.