| Light
Emitting Polymers (LEP) |
Definition
Light emitting polymers or polymer based light emitting diodes discovered by Friend
et al in 1990 has been found superior than other displays like, liquid crystal
displays (LCDs) vacuum fluorescence displays and electro luminescence displays.
Though not commercialised yet, these have proved to be a mile stone in the filed
of flat panel displays. Research in LEP is underway in Cambridge Display Technology
Ltd (CDT), the UK. In the last decade, several
other display contenders such as plasma and field emission displays were hailed
as the solution to the pervasive display. Like LCD they suited certain niche applications,
but failed to meet broad demands of the computer industry.
Today the trend is towards the non_crt flat panel displays. As LEDs are inexpensive
devices these can be extremely handy in constructing flat panel displays. The
idea was to combine the characteristics of a CRT with the performance of an LCD
and added design benefits of formability and low power. Cambridge Display Technology
Ltd is developing a display medium with exactly these characteristics.
The technology uses a light-emitting polymer (LEP) that costs much less to manufacture
and run than CRTs because the active material used is plastic. LEP
is a polymer that emits light when a voltage is applied to it. The structure comprises
a thin film semi conducting polymer sandwiched between two electrodes namely anode
and cathode. When electrons and holes are injected from the electrodes, the recombination
of these charge carriers takes place, which leads to emission of light that escape
through glass substrate.
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