Organic light-emitting diode

PLED

2007-12-27T15:17:00.005-08:00

Polymer light-emitting diodes (PLED), also Light-Emitting Polymers (LEP) involve an electroluminescent conductive polymer that emits light when subjected to an electric current. Developed by Cambridge Display Technology. They are used as a thin film for full-spectrum color displays and require a relatively small amount of power for the light produced. No vacuum is required, and the emissive materials can be applied on the substrate by a technique derived from commercial inkjet printing. The substrate used can be flexible, such as PET. Thus, flexible PLED displays may be produced inexpensively.

Typical polymers used in PLED displays include derivatives of poly(p-phenylene vinylene) and poly(fluorene). Substitution of side chains onto the polymer backbone may determine the color of emitted light or the stability and solubility of the polymer for performance and ease of processing.

Related technologies

2007-12-27T15:17:00.003-08:00

Small molecules

OLED technology was first developed at Eastman Kodak Company by Dr. Ching Tang using Small-molecules. The production of small-molecule displays requires vacuum deposition, which makes the production process more expensive than other processing techniques (see below). Since this is typically carried out on glass substrates, these displays are also not flexible, though this limitation is not inherent to small-molecule organic materials. The term OLED traditionally refers to this type of device, though some are using the term SM-OLED.

Molecules commonly used in OLEDs include organo-metallic chelates (for example Alq3, used in the first organic light-emitting device) and conjugated dendrimers.

Recently a hybrid light-emitting layer has been developed that uses nonconductive polymers doped with light-emitting, conductive molecules. The polymer is used for its production and mechanical advantages without worrying about optical properties. The small molecules then emit the light and have the same longevity that they have in the SM-OLEDs.

OLED

2007-12-27T15:17:00.001-08:00

An organic light-emitting diode (OLED), also Light Emitting Polymer (LEP) and Organic Electro-Luminescence (OEL), is any light-emitting diode (LED) whose emissive electroluminescent layer is composed of a film of organic compounds. The layer usually contains a polymer substance that allows suitable organic compounds to be deposited. They are deposited in rows and columns onto a flat carrier by a simple "printing" process. The resulting matrix of pixels can emit light of different colors.

Such systems can be used in television screens, computer displays, portable system screens, advertising, information and indication. OLEDs can also be used in light sources for general space illumination, and large-area light-emitting elements. OLEDs typically emit less light per area than inorganic solid-state based LEDs which are usually designed for use as point-light sources.

A great benefit of OLED displays over traditional liquid crystal displays (LCDs) is that OLEDs do not require a backlight to function. Thus they draw far less power and, when powered from a battery, can operate longer on the same charge. OLED-based display devices also can be more effectively manufactured than LCDs and plasma displays. But degradation of OLED materials has limited the use of these materials.