Thin film electroluminescent displays use a thin film of solid phosphor material that glows when electric current is applied. It is similar to a plasma display but uses phosphors like zinc sulfide doped with manganese instead of gas. Current intersections at row and column electrodes cause the phosphor to conduct and glow, emitting light. Advantages include high resolution and graphics but it requires more power and is expensive to produce good color and grayscales.

1. Thin Film Electroluminescent
Displays
Electroluminescent display uses a thin film of
solid, specially treated material that
glows in response to electric current.
Its construction is similar to plasma panel.
The diff is that , the region b/w the glass
plates is filled with a phosphors such as
zinc sulfide doped with manganese instead
of a gas.

2. To form a pixel on the screen, current is sent
to the intersection of appropriate row &
column. When voltage is applied to a pair
of crossing electrodes, the phosphors
become a conductor in the area of
intersection of the two electrodes.
Electrical energy is then absorbed by the
manganese atoms, which then release the
energy as a spot of light similar to the
glowing plasma effect in a plasma panel.

3. Advantages:
 Provides very high image resolution &
excellent graphic capability.
 These displays are bright & can be
switched on & off quickly.
Disadvantages:
 It require more power.
 Very Expensive.
 Good color & gray scale displays are hard
to achieve.

4. Light Emitting Diode (LED)
An LED is a unique type of semiconductor diode.
Like a normal diode, it consists of a chip of semi
-conducting material doped, with impurities to
create a p-n junction. As in other diodes, current
flows easily from the p-side, or anode, to the n-
side, or cathode, but not in the reverse direction.
Charge-carriers — electrons and electron holes
— flow into the junction from electrodes with
different voltages. When an electron meets a
hole, it falls into a lower energy level, and
releases energy in the form of a photon.

5. So we can say in LED a matrix of diodes is arranged
to form the pixel position in the display and the
picture definition is stored in a refresh buffer.
Additionally, they are housed in a plastic bulb that
concentrates the light in a particular direction.
As you can see in the diagram, most of the light from
the diode bounces off the sides of the bulb,
traveling on through the rounded end.

7. Applications of LED’s:
 Status indicators on all sorts of equipment
 Traffic lights and signals
 Exit signs
 Motorcycle and Bicycle lights
 Toys and sporting goods.
 Railroad crossing signals.
 Continuity indicators.
 Remote controls

8. Advantages:
 It provide a good light contrast.
 They don't have a filament that will burn
out, so they last much longer.
 Its small plastic bulb makes it a lot more
durable. They also fit more easily into
modern electronic circuits.
 It is efficient because LEDs generate very
little heat, A much higher percentage of the
electrical power is going directly to
generating light.