AMOLED

AMOLED (active-matrix organic light-emitting diode) is a display technology for use in mobile devices and televisions. OLED describes a specific type of thin-film display technology in which organic compounds form the electroluminescent material, and active matrix refers to the technology behind the addressing of pixels.

As of 2012, AMOLED technolog and continues to make progress toward low-power, low-cost and large-size (for example, 40-inch) applications.

Design

An AMOLED display consists of an active matrix of OLED pixels that generate light (luminescence) upon electrical activation that have been deposited or integrated onto a thin film transistor (TFT) array, which functions as a series of switches to control the current flowing to each individual pixel.

Typically, this continuous current flow is controlled by at least two TFTs at each pixel (to trigger the luminescence), with one TFT 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, thereby eliminating the need for the very high currents required for passive matrix OLED operation.

TFT backplane technology is crucial in the fabrication of AMOLED displays. Two primary TFT backplane technologies, namely polycrystalline silicon (poly-Si) and amorphous silicon (a-Si), are used today in AMOLEDs. These technologies offer the potential for fabricating the active matrix backplanes at low temperatures (below 150°C) directly onto flexible plastic substrates for producing flexible AMOLED displays.

Future development

Manufacturers have developed in-cell touch panels, integrating the production of capacitive sensor arrays in the AMOLED module fabrication process. In-cell sensor AMOLED fabricators include AU Optronics and Samsung. Samsung has marketed their version of this technology as Super AMOLED. Researchers at DuPont used computational fluid dynamics (CFD) software to optimize coating processes for a new solution-coated AMOLED display technology that is cost and performance competitive with existing chemical vapor deposition (CVD) technology. Using custom modeling and analytical approaches, they developed short- and long-range film-thickness control and uniformity that is commercially viable at large glass sizes.

Comparison to other technologies

AMOLED displays provide higher refresh rates than their passive-matrix OLED counterparts, improving response time often to under a millisecond, and they consume significantly less power. This advantage makes active-matrix OLEDs well suited for portable electronics, where power consumption is critical to battery life.

The amount of power the display consumes varies significantly depending on the colour and brightness shown. As an example, one commercial QVGA OLED display consumes 0.3 watts while showing white text on a black background, but more than 0.7 watts showing black text on a white background, while an LCD may consume only a constant 0.35 watts regardless of what is being shown on screen. Because the black pixels actually turn off, AMOLED also has contrast ratios that are significantly better than LCD.

AMOLED displays may be difficult to view in direct sunlight compared with LCDs because of their reduced maximum brightness. Samsung's Super AMOLED technology addresses this issue by reducing the size of gaps between layers of the screen. Additionally, PenTile technology is often used to allow for a higher resolution display while requiring fewer subpixels than would otherwise be needed, often resulting in a display less sharp and more grainy compared with a non-pentile display with the same resolution.

The organic materials used in AMOLED displays are prone to degradation over a period of time, resulting in color shifts as one color fades faster than another, image persistence or burn-in. However, technology has been developed to compensate for material degradation.

Current demand for AMOLED screens is high, and, due to supply shortages of the Samsung-produced displays, certain models of HTC smartphones have been changed to use next-generation LCD displays from the Samsung and Sony joint-venture SLCD in the future. Construction of new production facilities in 2011 will increase the production of AMOLED screens to cope with demand.

Marketing terms

 Super AMOLED

Super AMOLED is Samsung's term for an AMOLED display with an integrated digitizer, meaning, the layer that detects touch is integrated into the screen, rather than being overlaid on top of it. According to Samsung, Super AMOLED reflects 5 times less sunlight compared to the first generation AMOLED. The display technology itself is not changed. Super AMOLED is part of the Pentile Matrix Family.

Super AMOLED Advanced

Super AMOLED Advanced is a term marketed by Motorola to describe a brighter display than Super AMOLED screens, but also a higher resolution – qHD or 960 × 540 for Super AMOLED Advanced compared to WVGA or 800 × 480 for Super AMOLED. This display equips the Motorola Droid RAZR.

Super AMOLED Plus

The Samsung Galaxy S II, with a Super AMOLED Plus screen
Super AMOLED Plus, first introduced with the Samsung Galaxy S II and Samsung Droid Charge smartphones, is a branding from Samsung where the PenTile RGBG pixel matrix (2 subpixels) used in Super AMOLED displays has been replaced with a traditional RGB RGB (3 subpixels) arrangement typically used in LCD displays. This variant of AMOLED is brighter and therefore more energy efficient than Super AMOLED displays and produces a sharper, less grainy image because of the increased number of subpixels. In comparison to AMOLED and Super AMOLED displays, the Super AMOLED Plus displays are even more energy efficient and brighter.

HD Super AMOLED

Galaxy Note II subpixels representation, based on 400X image of the Note II display
The Galaxy Nexus, with an HD Super AMOLED screen
HD Super AMOLED is a branding from Samsung for an HD-resolution (>1280×720) Super AMOLED display. The first device to use it was the Samsung Galaxy Note. The Galaxy Nexus and the Galaxy S III both implement the HD Super AMOLED with a PenTile RGBG-matrix (2 subpixels/pixel), while the Galaxy Note II uses an RBG matrix (3 subpixels/pixel) but not in the standard 3 stripe arrangement.
Future

Future displays exhibited in 2012 have shown even higher resolutions with phone displays (4 to 5 inches) having Full HD (1920 × 1200 or 1920 × 1080) resolution capabilities.

From: http://en.wikipedia.org/wiki/AMOLED