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AMOLED

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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) 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 technology is used in mobile phones, media players and digital cameras,[1] and continues to make progress toward low-power, low-cost and large-size (for example, 40-inch) applications.[2][3][4]

Design

Schematic of an active matrix OLED display

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.[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. 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.[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 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.[8]

Comparison to other technologies

AMOLED displays provide higher refresh rates than their passive-matrix OLED counterparts[not specific enough to verify], improving response time often to under 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 colour and brightness shown. As an example, one commercial QVGA OLED display consumes 3 watts while showing black text on a white background, but only 0.7 watts showing white text on a black background.[10] 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.[11] Samsung's Super AMOLED technology addresses this issue by reducing the size of gaps between layers of the screen.[12][13] 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. However, technology has been developed to compensate for material degradation.[14][15]

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.[16] Construction of new production facilities in 2011 will increase the production of AMOLED screens to cope with demand.[17]

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.[18][19] The display technology itself is not changed. Also, Super AMOLED displays use a PenTile RGBG subpixel arrangement that has fewer subpixels than a traditional RGB RGB subpixel arrangement.[citation needed]

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.[citation needed]

Super AMOLED Plus

File:Samsung Galaxy S II in hand.jpg
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[20] 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.[citation needed]

HD Super AMOLED

Galaxy Note II subpixels representation, based on 400X image of the Note II display[21]
The Galaxy Nexus, with an HD Super AMOLED screen[22]

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 Note and the Galaxy S III both implement the HD Super AMOLED with a PenTile RGBG-matrix (2 subpixels/pexel) , while the Galaxy Note II uses an RBG matrix (3 subpixels/pixels) but not in the standard 3 stripe arrangement. [23]

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. It is debated whether such displays are justified given the extremely high pixel density involved. Such displays may use the same or different marketing terms when they are launched in phones.[citation needed]

Uses

Commercial devices using AMOLED include:[citation needed]

Phones
Tablets
Portable music players
Games consoles
Music production hardware
Digital cameras

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. 22 May 2008. Retrieved 6 September 2010.
  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. [1]
  8. ^ Reid Chesterfield, Andrew Johnson, Charlie Lang, Matthew Stainer, and Jonathan Ziebarth, "Solution-Coating Technology for AMOLED Displays", Information Display Magazine, January 2011.
  9. ^ Suyko, Alan. "Oleds Ready For The Mainstream." Electronics News (2009): 20. Associates Programs Source Plus. Web. 9 Dec. 2011.
  10. ^ Mian Dong; Choi, Y.-S.K; Lin Zhong (2009). "Power modeling of graphical user interfaces on OLED displays". Design Automation Conference, 2009. DAC '09. 46th ACM/IEEE. IEEE: 652–657. {{cite journal}}: Unknown parameter |month= ignored (help)
  11. ^ How Super AMOLED displays work
  12. ^ "What Are The Benefits Of Using The Super AMOLED Display In My SGH-t959 (Vibrant) Phone?". Samsung. 15 July 2010. Retrieved 7 September 2010.
  13. ^ "Big is beautiful". The Age. 12 August 2010. Archived from the original on 29 August 2010. Retrieved 7 September 2010. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  14. ^ 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.
  15. ^ US 7352345, Chun-huai Li, "Driving apparatus and method for light emitting diode display", issued 2008-04-01 
  16. ^ "HTC ditches Samsung AMOLED display for Sony's Super LCDs". International Business Times. 26 July 2010. Retrieved 1 January 2011.
  17. ^ "Samsung Mobile Display to Boost 2011 Production". Wall Street Journal. 6 September 2010. Retrieved 1 January 2011.
  18. ^ http://www.samsung.com/au/smartphone/technology/super-amoled.html
  19. ^ http://www.oled-info.com/super-amoled
  20. ^ "http://www.oled-info.com/super-amoled-plus". OLED-Info. Retrieved 23 August 2011. {{cite web}}: External link in |title= (help)
  21. ^ http://bestboyz.de/galaxy-note-2-display-hat-keine-pentile-matrix/
  22. ^ http://www.samsung.com/uk/consumer/mobile-devices/smartphones/android/GT-I9250TSAXEU
  23. ^ http://bestboyz.de/galaxy-note-2-display-hat-keine-pentile-matrix/

External links

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