AMOLED

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

AMOLED (active-matrix organic light-emitting diode, /ˈæmoʊˌlɛd/) is a display technology used in smartwatches, mobile devices, laptops, 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 2008, AMOLED technology was used in mobile phones, media players and digital cameras[1] and continued to make progress toward low-power, low-cost and large-size (for example, 40-inch or 100-centimeter) applications.[2][3][4]

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]

Disadvantages

Red and green OLED films have longer lifespans compared to blue OLED films. This variation results in color shifts as a particular pixel fades faster than the other pixels. This is amplified with the effect of pixel burn-in, and that blue pixels are used very frequently.[8]

AMOLED displays are prone to screen burn-in, which leaves a permanent imprint of overused colors represented by overused images. This usually only happens if the screen is used at maximum brightness the majority of the time for a long time.[8]

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.[9]

Comparison to other technologies

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.[10] 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.[11] Because the black pixels turn completely off, AMOLED also has contrast ratios that are significantly higher than LCD.[12]

AMOLED displays may be difficult to view in direct sunlight compared with LCDs because of their reduced maximum brightness.[13] Samsung's Super AMOLED technology addresses this issue by reducing the size of gaps between layers of the screen.[14][15] 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.[16][17]

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.[18]

Flagship smartphones sold as of December 2011 used either Super AMOLED or IPS panel premium 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.[19][20][21] 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.[22] 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[23]

Super AMOLED

"Super AMOLED" is a marketing term created by device manufacturers for an AMOLED display with an integrated digitizer: the layer that detects touch is integrated into the screen, rather than overlaid on top of it. The display technology itself is not improved. According to Samsung, Super AMOLED reflects one-fifth as much sunlight as the first generation AMOLED.[24][25] 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.[26]

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.[27] This display type is used on the Motorola Droid RAZR and HTC One S.[28]

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 LCDs. This variant of AMOLED is brighter and therefore more energy efficient than Super AMOLED displays[29] 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.[20]

HD Super AMOLED

HD Super AMOLED is a 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.[23]

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.[30]

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.[31][32]

Quad HD Super AMOLED

Quad HD Super AMOLED technology was first used by AU Optronics in April 2014.[33] 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, unbreakable, 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.[34]

So far, Samsung plans on branding the newer displays as Youm[35], or y-octa[36]

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
(inch)		 PPI Pixel
Layout		 used in
AMOLED 240×320 2.6 154 RGBG PenTile Nokia N85
AMOLED
Capacitive Touchscreen		 640×360 3.2 229 Nokia C6-01
Super AMOLED 3.5 210 RGB S-Stripe Nokia N8
4.0 184 Nokia 808 PureView
720×720 3.1 328 BlackBerry Q10
854×480 3.9 251 RGBG PenTile Nokia N9
800×480 4.0 233 Samsung Galaxy S
960×540 4.3 256 RGB S-Stripe Samsung Galaxy S4 Mini
1280×768 4.5 332 RGBG PenTile Nokia Lumia 1020
Super AMOLED Plus 800×480 4.3 (4.27) 218 RGB stripe Samsung Galaxy S II
Super AMOLED Advanced 960×540 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
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 OnePlus 5T
Super Retina HD 2436×1125 5.8 458 Apple iPhone X
Apple iPhone Xs
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
6.2 529 Samsung Galaxy S8+
6.3 521 Samsung Galaxy Note 8
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[37]

Uses

Commercial devices using AMOLED include:

Smartwatches

Phones

Tablets

Portable music players

Games consoles

Music production hardware

Digital cameras[40][41]

References

  1. ↑ Lee, Hyunkoo; Park, Insun; Kwak, Jeonghun; Yoon, Do Y.; Kallmann, Changhee Lee (2010). "Improvement of electron injection in inverted bottom-emission blue phosphorescent organic light emitting diodes using zinc oxide nanoparticles". Applied Physics Letters. 96: 153306. doi:10.1063/1.3400224.
  2. ↑ Kim, Yang Wan; Kwak, Won Kyu; Lee, Jae Yong; Choi, Wong Sik; Lee, Ki Yong; Kim, Sung Chul; Yoo, Eui Jin (2009). "40 Inch FHD AM-OLED Display with IR Drop Compensation Pixel Circuit". SID Symposium Digest of Technical Papers. 40: 85. doi:10.1889/1.3256930.
  3. ↑ Lee, Myung Ho; Seop, Song Myoung; Kim, Jong Soo; Hwang, Jung Ho; Shin, Hye Jin; Cho, Sang Kyun; Min, Kyoung Wook; Kwak, Won Kyu; Jung, Sun I; Kim, Chang Soo; Choi, Woong Sik; Kim, Sung Cheol; Yoo, Eu Jin (2009). "Development of 31-Inch Full-HD AMOLED TV Using LTPS-TFT and RGB FMM". SID Symposium Digest of Technical Papers. 40: 802. doi:10.1889/1.3256911.
  4. ↑ Hamer, John W.; Arnold, Andrew D.; Boroson, Michael L.; Itoh, Masahiro; Hatwar, Tukaram K.; Helber, Margaret J.; Miwa, Koichi; Levey, Charles I.; Long, Michael; Ludwicki, John E.; Scheirer, David C.; Spindler, Jeffrey P.; Van Slyke, Steven A. (2008). "System design for a wide-color-gamut TV-sized AMOLED display". Journal of the Society for Information Display. 16: 3. doi:10.1889/1.2835033.
  5. ↑ "Introduction to OLED Displays – Design Guide for Active Matrix OLED (AMOLED) Displays" (PDF). 4D Systems. 2008-05-22. Archived from the original (PDF) on 5 July 2010. Retrieved 2010-09-06.
  6. ↑ Lin, Chih-Lung; Chen, Yung-Chih. "A Novel LTPS-TFT Pixel Circuit Compensating for TFT Threshold-Voltage Shift and OLED Degradation for AMOLED". IEEE Electron Device Letters. 28: 129. doi:10.1109/LED.2006.889523.
  7. ↑ Sarma, Kalluri R.; Chanley, Charles; Dodd, Sonia R.; Roush, Jared; Schmidt, John; Srdanov, Gordana; Stevenson, Matthew; Wessel, Ralf; Innocenzo, Jeffrey; Yu, Gang; O'Regan, Marie B.; MacDonald, W. A.; Eveson, R.; Long, Ke; Gleskova, Helena; Wagner, Sigurd; Sturm, James C. (2003). "Active-matrix OLED using 150°C a-Si TFT backplane built on flexible plastic substrate (Proceedings Paper)". SPIE Proceedings. 5080: 180. doi:10.1117/12.497638. "Archived copy" (PDF). Archived from the original (PDF) on 28 June 2011. Retrieved 2010-09-06.
  8. 1 2 "Advantages and disadvantages of AMOLED". Version Daily. 3 December 2015. Archived from the original on 20 January 2016. Retrieved 3 December 2015.
  9. ↑ Reid Chesterfield, Andrew Johnson, Charlie Lang, Matthew Stainer, and Jonathan Ziebarth, "Solution-Coating Technology for AMOLED Displays Archived 16 May 2011 at the Wayback Machine.", Information Display Magazine, January 2011.
  10. ↑ Suyko, Alan. "Oleds Ready For The Mainstream." Electronics News (2009): 20. Associates Programs Source Plus. Web. 9 Dec. 2011.
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  12. ↑ "AMOLED vs LCD: differences explained". Android Authority. Archived from the original on 27 December 2016. Retrieved 6 February 2017.
  13. ↑ Tim CarmodyEmail Author. "How Super AMOLED displays work". Wired.com. Archived from the original on 28 September 2012. Retrieved 10 October 2012.
  14. ↑ "What Are The Benefits Of Using The Super AMOLED Display In My SGH-t959 (Vibrant) Phone?". Samsung. 2010-07-15. Archived from the original on 2011-07-16. Retrieved 2010-09-07.
  15. ↑ "Big is beautiful". The Age. 12 August 2010. Archived from the original on 29 August 2010. Retrieved 7 September 2010.
  16. ↑ Ashtiani, Shahin J.; Reza Chaji, G.; Nathan, Arokia. "AMOLED Pixel Circuit With Electronic Compensation of Luminance Degradation". Journal of Display Technology. 38: 36. doi:10.1109/JDT.2006.890711.
  17. ↑ US 7352345, Chun-huai Li, "Driving apparatus and method for light emitting diode display", issued 2008-04-01
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  20. 1 2 "Smartphone screens explained: display types, resolutions and more - AndroidPIT". androidpit.com. Archived from the original on 12 May 2015. Retrieved 6 May 2018.
  21. ↑ "Nexus 4 Review: Not Exactly Perfect, But Close Enough For Me – TechCrunch". techcrunch.com. Archived from the original on 7 February 2018. Retrieved 6 May 2018.
  22. ↑ Google/Motorola Mobility Display a Bright Efficient Future, ABI Research
  23. 1 2 "Galaxy Note 2: Display hat keine PenTile-Matrix | BestBoyZ". Bestboyz.de. 30 August 2012. Archived from the original on 10 October 2012. Retrieved 10 October 2012.
  24. ↑ "Samsung Smartphones | Technology". Samsung.com. 6 January 2012. Archived from the original on 27 June 2012. Retrieved 10 October 2012.
  25. ↑ "Super AMOLED". Oled-info.com. Archived from the original on 9 October 2012. Retrieved 10 October 2012.
  26. ↑ Sakr, Sharif (25 March 2012). "Samsung Galaxy S III review". Engadget. Archived from the original on 26 January 2013. Retrieved 6 February 2013.
  27. ↑ "Super AMOLED Advanced". Archived from the original on 24 March 2014. Retrieved 24 March 2014.
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  29. ↑ "www.oled-info.com/super-amoled-plus". OLED-Info. Archived from the original on 16 August 2011. Retrieved 23 August 2011.
  30. ↑ "WiFi Alliance certificate teases Tizen flavored Samsung Galaxy S III". engadget.com. Archived from the original on 11 October 2016. Retrieved 6 May 2018.
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  36. ↑ Kelly, Gordon. "Samsung Report 'Confirms' Significant Galaxy S9 Design Changes". forbes.com. Archived from the original on 1 April 2018. Retrieved 6 May 2018.
  37. ↑ "HTC VIVE Focus". vive.com. Archived from the original on 13 December 2017. Retrieved 13 December 2017.
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