Active-Matrix OLED
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AMOLED is the acronym for active-matrix organic light-emitting diode, an emerging display technology for use in mobile devices like mobile phones. OLED describes a specific type of ultra thin, ultra bright display technology which doesn't require a backlight and AMOLED refers to the technology behind the addressing of pixels. AMOLED technology continues to make progress towards low-power and low-cost large size (e.g. 40-inch) for applications such as TV.
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[edit] Technical Explanation
An active-matrix OLED (AMOLED) display consists of OLED pixels that have been deposited or integrated onto a thin film transistor (TFT) array to form a matrix of pixels that illuminate light upon electrical activation, which functions as a series of switches to control the current flowing to each of the pixels. The TFT array continuously controls the current that flows to the pixels, signaling to each pixel how brightly to shine.[citation needed]
Typically, this continuous current flow is controlled by at least two TFTs at each pixel, one to start and stop the charging of a storage capacitor and the second to provide a voltage source at the level needed to create a constant current to the pixel and eliminating need for the very high currents required for passive OLED matrix operation.[citation needed]
AMOLED screens have four separate layers to control the picture:[citation needed]
[edit] Characteristics
Active-matrix OLED displays provide the same video-rate performance as their passive-matrix OLED counterparts, but they consume significantly less power.[citation needed]
This advantage makes active-matrix OLEDs well suited[clarification needed] for portable electronics, where battery power consumption is critical, and for displays that are larger than 2” to 3” diagonally.[citation needed]
When the display gets bent with a radius smaller than the critical radius, it leads to cracking of the overcoat layer on the plastic substrate, and this crack propagates through the address bus lines. The cracked bus structures cause the displays to exhibit intermittent line failures, gross line failures, or large regions of non-functioning areas including complete display failure.
[edit] Advantages
AMOLED displays fabricated on flexible plastic substrates have the following advantages:[citation needed]
- Very thin and lighter weight
- Greatly minimized propensity for breakage
- Lower-power, highly rugged with superior image quality, and low cost compared to the current LCD displays
- Due to their inherent ruggedness, allow a unique form factor of conformability and rollability during use, transportation and storage.
[edit] Main Disadvantages
AMOLED displays are prone to very low life span. Independent laboratory studies conducted on one of the commercial AMOLED screen taken from a mobile phone shows that after about 200 hours, the brightness is reduced to 50% of original.
[edit] Active Matrix Element:TFT Backplane Technology
TFT backplane technology is a crucial enabler for the fabrication of flexible AM OLED displays.
The conventional glass substrate based TFT process cannot be used with the flexible plastic substrates, primarily because of the low temperature process constraint.[citation needed]
Two primary TFT backplane technologies (poly-Silicon (poly-Si) and amorphous-Silicon (a-Si)) are used today in AMOLEDs. These technologies offer the potential for fabricating the required active matrix backplanes at low temperatures (< 150°C) directly on the flexible plastic substrate for producing flexible AM OLED displays.
[edit] External links
- Examples of AMOLED displays
- MP3 Players with AMOLED screens
- [1]Samsung I7500: The first Samsung Android phone with HVGA AMOLED touch screen
