AMOLED

AMOLED (active-matrix organic light-emitting diode, /ˈæmˌlɛd/) is a type of OLED display device technology. 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.

Magnified image of the AMOLED screen on the Nexus One smartphone using the RGBG system of the PenTile matrix family

Since 2007, AMOLED technology has been used in mobile phones, media players, TVs and digital cameras,[1] and it has continued to make progress toward low-power, low-cost, high resolution and large size (for example, 88-inch and 8K resolution) applications.[2][3][4]

Dynamic AMOLED displays used in Samsung Galaxy Note 10 smartphones

Design

Schematic of an active-matrix OLED display

An AMOLED display consists of an active matrix of OLED pixels generating 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.[5]

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.[6]

TFT backplane technology is crucial in the fabrication of AMOLED displays. In AMOLEDs, the two primary TFT backplane technologies, polycrystalline silicon (poly-Si) and amorphous silicon (a-Si), are currently used offering the potential for directly fabricating the active-matrix backplanes at low temperatures (below 150 °C) onto flexible plastic substrates for producing flexible AMOLED displays.[7]

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 its 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 competitive in cost and performance with existing chemical vapor deposition (CVD) technology. Using custom modeling and analytic approaches, Samsung has developed short and long-range film-thickness control and uniformity that is commercially viable at large glass sizes.[8]

Comparison to other display technologies

Compared to other display technologies, AMOLED screens have several advantages and disadvantages.

AMOLED displays provide higher refresh rates than passive-matrix, often reducing the response time to less than a millisecond, and they consume significantly less power.[9] 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 color 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.[10] Because the black pixels turn completely off, AMOLED also has contrast ratios that are significantly higher than LCD.[11]

AMOLED displays may be difficult to view in direct sunlight compared with LCDs because of their reduced maximum brightness.[12] Samsung's Super AMOLED technology addresses this issue by reducing the size of gaps between layers of the screen.[13][14] Additionally, PenTile technology is often used for a higher resolution display while requiring fewer subpixels than needed otherwise, sometimes resulting in a display less sharp and more grainy than a non-PenTile display with the same resolution.

The organic materials used in AMOLED displays are very prone to degradation over a relatively short period of time, resulting in color shifts as one color fades faster than another, image persistence, or burn-in.[15][16]

As of 2010, demand for AMOLED screens was high and, due to supply shortages of the Samsung-produced displays, certain models of HTC smartphones were changed to use next-generation LCD displays from the Samsung-Sony joint-venture SLCD in the future.[17]

Flagship smartphones sold as of December 2011 used either a Super AMOLED or an IPS panel LCD. Super AMOLED displays, such as the one on the Galaxy Nexus and Samsung Galaxy S III have often been compared to IPS panel premium LCDs, found in the iPhone 4S, HTC One X, and Nexus 4.[18][19][20] For example, according to ABI Research the AMOLED display found in the Motorola Moto X draws just 92 mA during bright conditions and 68 mA while dim.[21] On the other hand, compared with the IPS, the yield rate of AMOLED is low; the cost is also higher.

Marketing terms

Galaxy Note II subpixels representation, based on 400X image of the Note II display[22]

Super AMOLED

"Super AMOLED" is a marketing term created by Samsung for an AMOLED display with an integrated touch screen digitizer: the layer that detects touch is integrated into the display, rather than overlaid on top of it and cannot be separated from the display itself. The display technology itself is not improved. According to Samsung, Super AMOLED reflects one-fifth as much sunlight as the first generation AMOLED.[23][24] Super AMOLED is part of the Pentile matrix family, sometimes abbreviated as sAMOLED. For the Samsung Galaxy S III, which reverted to Super AMOLED instead of the pixelation-free conventional RGB (non-PenTile) Super AMOLED Plus of its predecessor Samsung Galaxy S II, the S III's larger screen size encourages users to hold the phone further from their face to obscure the PenTile effect.[25]

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 than WVGA or 800×480 for Super AMOLED and 25% more energy efficient. Super AMOLED Advanced features PenTile, which sharpens subpixels in between pixels to make a higher resolution display, but by doing this, some picture quality is lost.[26] This display type is used on the Motorola Droid RAZR and HTC One S.[27]

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 have been replaced with a traditional RGB RGB (3 subpixels) arrangement typically used in LCDs. This variant of AMOLED is brighter and therefore more energy-efficient than Super AMOLED displays[28] and produces a sharper, less grainy image because of the increased number of subpixels. In comparison to AMOLED and Super AMOLED displays, they are even more energy-efficient and brighter. However, Samsung cited screen life and costs by not using Plus on the Galaxy S II's successor, the Samsung Galaxy S III.[19]

HD Super AMOLED

HD Super AMOLED is branding from Samsung for an HD-resolution (above 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.[22]

HD Super AMOLED Plus

A variant of the Samsung Galaxy S3 using Tizen OS 1 was benchmarked using a non-pentile HD Super AMOLED Plus screen in 2012.[29]

Full HD Super AMOLED

As featured on the Samsung Galaxy S4, Samsung Galaxy S5, and Samsung Galaxy Note 3, this display has a 1920×1080 resolution that is better known as 1080p. It has a color gamut of up to 97% of the Adobe RGB color space.[30][31] It is currently used on wide range of Samsung smartphones since 2017.

Quad HD Super AMOLED

Quad HD Super AMOLED technology was first used by AU Optronics in April 2014.[32] After AU Optronics released their phone which used a Quad HD Super AMOLED screen, other companies such as Samsung released phones utilizing the technology such as the Samsung Galaxy Note 4 and Samsung Galaxy Note 5 Broadband LTE-A and Samsung Galaxy S6 and S7.

Future

Future displays exhibited from 2011 to 2013 by Samsung have shown flexible, 3D, transparent Super AMOLED Plus displays using very high resolutions and in varying sizes for phones. These unreleased prototypes use a polymer as a substrate removing the need for glass cover, a metal backing, and touch matrix, combining them into one integrated layer.[33]

So far, Samsung plans on branding the newer displays as Youm,[34] or y-octa.[35]

Also planned for the future are 3D stereoscopic displays that use eye-tracking (via stereoscopic front-facing cameras) to provide full resolution 3D visuals.

Comparison

Below is a mapping table of marketing terms versus resolutions and sub-pixel types. Note how the pixel density relates to choices of sub-pixel type.

Term Reso-
lution
Size
(inches)
PPI Pixel
layout
Used in
AMOLED 0240×320 2.6 154 RGBG PenTile Nokia N85
AMOLED
Capacitive Touchscreen
0640×360 3.2 229 Nokia C6-01
Super AMOLED 3.5 210 RGB S-Stripe Nokia N8
4.0 184 Nokia 808 PureView
0720×720 3.1 328 BlackBerry Q10
0854×480 3.9 251 RGBG PenTile Nokia N9
0800×480 4.0 233 Samsung Galaxy S
0960×540 4.3 256 RGB S-Stripe Samsung Galaxy S4 Mini
1280×768 4.5 332 RGBG PenTile Nokia Lumia 1020
Super AMOLED Plus 0800×480 4.3 (4.27) 218 RGB stripe Samsung Galaxy S II
Super AMOLED Advanced 0960×540 4.3 256 RGBG PenTile Motorola Droid RAZR
HD Super AMOLED 1280×800 5.3 (5.29) 285 Samsung Galaxy Note
1280×720 5.0 295 RGB S-Stripe BlackBerry Z30
Samsung Galaxy J7
Samsung Galaxy J5
Samsung Galaxy E5
Samsung Galaxy J3 (2016)
4.7 (4.65) 316 RGBG PenTile Samsung Galaxy Nexus
4.7 (4.65) 316 RGB S-Stripe Moto X (1st generation)
4.8 306 RGBG PenTile Samsung Galaxy S III
5.6 (5.55) 267 RGB S-Stripe Samsung Galaxy Note II
5.6 (5.55) 267 Samsung Galaxy Note 3 Neo
HD Super AMOLED Plus 1280×800 7.7 197 RGB stripe Samsung Galaxy Tab 7.7
Full HD Super AMOLED 1920×1080 5.5 400 RGBG PenTile Meizu MX5
5.0 (4.99) 441 Samsung Galaxy S4
5.0 (4.99) 441 OnePlus X
5.0 (4.99) 441 Google Pixel
5.2 423 Motorola Moto X (2nd gen)
5.1 432 Samsung Galaxy S5
5.5 401 OnePlus 3
OnePlus 3T
OnePlus 5
5.7 388 Samsung Galaxy Note 3
Full HD+ Super AMOLED 2160×1080 6.0 402 Huawei Mate 10 Pro
6.01 401 Google Pixel 3
Super Retina HD 2436×1125 5.8 (5.85) 458 Apple iPhone X
iPhone XS
iPhone 11 Pro
2688×1242 6.5 (6.46) iPhone XS Max
iPhone 11 Pro Max
WQHD Super AMOLED 2560×1440 5.1 577 Samsung Galaxy S6
Samsung Galaxy S6 Edge
Samsung Galaxy S6 Active
Samsung Galaxy S7
Samsung Galaxy S7 Active
5.2 564 Microsoft Lumia 950
5.2 565 Motorola Droid Turbo
5.4 540 BlackBerry Priv
5.5 534 BlackBerry DTEK60
Samsung Galaxy S7 Edge
Google Pixel XL
Alcatel Idol 4S
vodafone smart platinum 7(Alcatel Sol Prime)
Moto Z
Moto Z Force
ZTE Axon 7
5.7 515 Samsung Galaxy Note 4
Samsung Galaxy Note 5
Samsung Galaxy S6 Edge+
Nexus 6P
Samsung Galaxy Note 7
5.7 518 Microsoft Lumia 950 XL
2960×1440 5.8 571 Samsung Galaxy S8
Samsung Galaxy S9
6.2 529 Samsung Galaxy S8+
Samsung Galaxy S9+
6.3 521 Samsung Galaxy Note 8
6.4 514 Samsung Galaxy Note 9
WQXGA Super AMOLED 2560×1600 8.4 359 RGBG PenTile Samsung Galaxy Tab S 8.4
10.5 287 RGB S-Stripe Samsung Galaxy Tab S 10.5
3K AMOLED 2880×1600 (unknown) HTC Vive Focus[36]
Dynamic AMOLED 2280x1080

3040x1440

2280x1080

3040x1440

3040x1440

5.8

6.1

6.3

6.4

6.8

438

550

401

522

498

Samsung Galaxy S10e

Samsung Galaxy S10

Samsung Galaxy Note 10

Samsung Galaxy S10+

Samsung Galaxy Note 10+

Dynamic AMOLED 2X 2208×1768

2400x1080

3200x1440

7.6

6.1

6.4

6.8

Samsung Galaxy Fold 2

Samsung Galaxy S20

Samsung Galaxy S20+

Samsung Galaxy S20 Ultra

Samsung Galaxy S21

Samsung Galaxy S21+

Samsung Galaxy S21 Ultra

Fluid AMOLED 1440×3120 6.67 516 OnePlus 7 Pro

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