One of the next trends in display technology is Organic Light Emitting Diodes (OLEDs). Polymer Light Emitting Diodes (PLEDs), Small Molecule Light Emitting Diodes (SMOLEDS) and dendrimer technology are all variations of OLEDs. With all variations being made by electroluminescent substances (substances that emit light when excited by an electric current), OLED displays are brighter, offer more contrast, consume less power, and offer large viewing angles – all areas where LCDs fall short.
OLEDs are composed of light-emitting organic material sandwiched between two conducting plates, one of n-type material and one of p-type material. The molecular structure in the n-type material, although electrically neutral, has an extra electron that is relatively free to move around the material. In p-type material the opposite is true. The lack of an electron creates a hole that is free to move about. The creation of the extra electron or the hole comes about because of the mismatch of valence electrons in the molecular structure of the p or n-type material.
An organic light-emitting diode (OLED) is a light-emitting diode (LED) in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current. This layer of organic semiconductor is situated between two electrodes; typically, at least one of these electrodes is transparent. OLEDs are used to create digital displays in devices such as television screens, computer monitors, and portable systems such as mobile phones, handheld game consoles and PDAs. A major area of research is the development of white OLED devices for use in solid-state lighting applications.
There are two main families of OLED:- one is based on small molecules and the other those employing polymers. Adding mobile ions to an OLED creates a light-emitting electrochemical cell (LEC) which has a slightly different mode of operation. An OLED display can be driven with a passive-matrix (PMOLED) or active-matrix (AMOLED) control scheme. In the PMOLED scheme, each row (and line) in the display is controlled sequentially, one by one, whereas AMOLED control uses a thin-film transistor backplane to directly access and switches each individual pixel on or off, allowing for higher resolution and larger display sizes. An OLED display works without a backlight thus it can display deep black levels and can be thinner and lighter than a liquid crystal display (LCD). In low ambient light conditions (such as a dark room), an OLED screen can achieve a higher contrast ratio than an LCD, regardless of whether the LCD uses cold cathode fluorescent lamps or an LED backlight.Return to main Display Technology page