TFT
Short for
thin film transistor, a type of LCD flat-panel display screen, in which each
pixel is controlled by from one to four transistors. The TFT technology
provides the best resolution of all the flat-panel techniques, but it is also
the most expensive. TFT screens are sometimes called active-matrix LCDs. A thin
film transistor comprises :
a
semiconductor layer
a gate
insulating layer
a gate
electrode
The
semiconductor layer is typically a polysilicon layer whose electron mobility is
100 times higher than that of an amorphous silicon layer. Thin film transistors
are used as switching devices in flat display panels such as organic light
emitting diodes (OLEDs) or liquid crystal displays (LCDs).
- Types of TFT:-
IPS -
in-plane switching.
MVA - multi-domain
vertical alignment
VA -
patterned vertical alignment
CPA - Continuous
Pinwheel Alignment
- Advantages of using it:-
1.Can be
used as electrodes, or channel layers.
2.High field
effect mobility : 10 ~ 5
3.Large area
deposition.
4.Rapid
Process.
5.Low
cost.
6.Low leakage current.
AMOLED
It stands
for Active Matrix OLED, is a hybrid display technology that pairs the active
matrix backplane from a traditional TFT display with an OLED display. As a
result of their active matrix natures, AMOLED displays have faster pixel
switching response times than do traditional OLED displays, which are prone to
ghosting when displaying fast moving animations.
- Advantages
Higher image
resolution. Richer and more vibrant colors. AMOLED uses less voltage, and
devices employing AMOLED technology have better battery life. AMOLED also
manages to save battery by turning off pixels to display black pixels in an
image. The displays are thinner and lighter than LCD or LED.
- Disadvantages
The current
market for AMOLED devices is almost exclusively in handheld electronics due to
the manufacturing difficulties associated with creating larger displays. For
instance, making AMOLD available for larger flat screen televisions would
require and overhaul in the manufacturing process of the back panels.
- How AMOLED works?
By employing
an active matrix to control a system of OLED nodes, each being assigned an individual
pixel in the display. The matrix is applied to a back panel, called a Thin Film
Transistor, which regulates to flow of electrons to each individual pixel. The
back panel is made of polycrystalline silicon and amorphous silicon. Two back
panel layers will typically be employed; one acting as a voltage source and the
other as a capacitor. The flow from layer to layer can be individually
regulated, so for instance, a given pixel can shut itself off to render black.
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