Organic light emitting diodes (OLEDs) are optoelectronic devices based on small molecules or polymers that emit light when an electric current flows through them. simple OLED consists of a fluorescent organic layer sandwiched between two metal electrodes.Under application of an electric field, electrons and holes are injected from the two electrodes into the organic layer, where they meet and recombine to produce light. They have been developed for applications in flat panel displays that provide visual imagery that is easy to read, vibrant in colors and less consuming of power.

OLEDs are used in television screens, computer monitors, small, portable system screens such as mobile phones and PDAs, watches, advertising, information and indication. OLEDs are also used in light sources for general space illumination and in large-area light-emitting elements. Due to their comparatively early stage of development, they typically emit less light per unit area than inorganic solid-state LED light sources.

An OLED display functions without a backlight. Thus, it can display deep black levels and can also be thinner and lighter than established liquid crystal displays. Similarly, in low ambient light conditions such as dark rooms, an OLED screen can achieve a higher contrast ratio than an LCD screen using either cold cathode fluorescent lamps or the more recently developed LED backlight.

There are two main families of OLEDs: those based upon small molecules and those employing polymers. Adding mobile ions to an OLED creates a Light-emitting Electrochemical Cell (LEC), which has a slightly different mode of operation.

OLED displays can use either passive-matrix or active-matrix addressing schemes. Active-matrix OLEDs (AMOLED) require a thin-film transistor backplane to switch each individual pixel on or off, and can make higher resolution and larger size displays possible.

The different manufacturing process of OLEDs lends itself to several advantages over flat-panel displays made with LCD technology.

Advantages of AMOLED & PMOLED:

  • Light weight & flexible plastic substrates
  • Wider viewing angles & improved brightness
  • Better power efficiency
  • Faster response time for full motion video
  • Broader operating temperature ranges
  • Greater brightness
  • Future low cost

Drawbacks of AMOLED & PMOLED:

  • Limited lifetime of the organic materials
  • OLED material used to produce blue light degrades significantly more rapidly than the materials that produce other colors
  • Water can damage the organic materials of the displays
  • Outdoor performance is poor
  • Power consumption is comparable to that of an LCD display
  • Screen burn-in: brightness of each OLED pixel fades depending on the content displayed