In 2010, Samsung introduced a premium touchscreen-enabled, slate-format Android smartphone with a display panel that featured deep blacks and high contrast. With vivid colours, images that came to life, and wide viewing angle, the visual experience was incomparable.
The Samsung Galaxy S rocked an active-matrix organic light-emitting diode or AMOLED screen. Critics and general consumers gave the device a positive rating for introducing and popularising an innovative display technology. As a backgrounder, AMOLED is a display technology now used in several consumer electronic products to include mobile devices and television. Samsung popularised the use of this technology and has since became a standard feature of some of its flagship smartphones and tablets, as well as digital cameras and smart televisions.
An AMOLED display technology is an advanced iteration to organic light-emitting diode technology—an electroluminescent technology made of a thin film of organic compounds that emit light in response to an electric current. Note that electroluminescence is an optical and electrical phenomenon that results from the excitation of electrons due to the passage of an electric current or a strong electric field that in turn, releases their energy as photons. In OLED technology, organic-based compounds produce this electroluminescence.
The application of OLED technology in display panels requires the simultaneous switching of individual organic compounds, each representing an individual picture element or pixel. An AMOLED display technology addresses this through active matrix switching, particularly by attaching each pixel to a transistor and capacitor to actively maintain the pixel state while addressing other pixels.
Advantages of AMOLED display technology
One advantage of AMOLED display is thinness. A typical AMOLED display has an organic plastic layer that is about 100 to 500 nanometres thick. This is about 200 times thinner than the strand of human hair, thus making it thinner, lighter, and more flexible than the crystalline layers of LED or LCD display. This thinness also produces brighter luminescence compared to LED.
Energy efficiency is another advantage of AMOLED display. It is more energy efficiency than LED and LCD, as well as fluorescent lamps for numerous reasons. Because they emit light without generating too much heat, energy loss due to heat transfer is lesser.
An AMOLED display also does not require backlighting unlike LCD because each pixel of organic material generates light itself. Within the same display, power consumption is uneven, focusing mostly on active pixels as represented by on-screen image. Blacks do not consume power because the underlying pixels are actually turned off.
Thus, an AMOLED screen display consumes less power, making it more appropriate for use in portable consumer electronic devices in which battery life is of critical importance. Furthermore, because of this energy efficiency, eco-friendliness is another advantage of AMOLED over its counterparts.
The images produced by an AMOLED display are remarkable and incomparable due to its deep blacks and high contrast. This advantage is noticeable when compared to other LOCD display technologies such as in-plane switching display or IPS or twisted nematic or TN display technologies.
Because each pixel of organic material emit light, the entire display has greater artificial contrast ratio measurable in pure dark conditions and has better viewing angle compared to an LCD. The display is also more responsive due to a higher refresh rate than LCD making moving images more fluid and less straining to the eyes.
Disadvantages of AMOLED display technology
Tenured users of Samsung Galaxy S and Galaxy Note line of smartphones could attest to the fact that the quality of their screen display had degraded overtime. This is one of the major disadvantages of AMOLED display. Organic materials have limited lifespan, far shorter than the lifespan of LED or LCD.
In addition, lifespans of each colour-specific organic material varies. Red and green OLED films have longer lifespans compared to blue OLED films. This variation results in colour shifts as a particular pixel fades faster than the other pixels.
Because of overall shorter lifespan and variations in the lifespan of colour-specific organic materials, AMOLED displays are very prone to screen burn-in, which leaves a permanent imprint of overused colours represented by overused images.
Organic compounds are also highly susceptible to water damages unlike light diodes or inorganic crystalline. Submerging an AMOLED display in water would result in immediate loss of some colours represented by burn-in or dead pixels. This susceptibility makes sealing processes an important consideration in fabrication and manufacturing.
Compared with an LCD, an AMOLED display is difficult to view in direct sunlight due to reduced maximum brightness and lack of backlighting. There have been several workarounds to this problem including reducing the size of gaps between the layers of screen to reduce reflectivity.
Another disadvantage of AMOLED display is cost. Manufacturing this display technology can be costly due to the complexity in fabricating substrates. The individual parts of the same display can also be costly and assembling them together remains much more expensive than LCD manufacturing.
Nonetheless, despite the disadvantages of an AMOLED display, the entire display technology remains popular in several consumer electronics—even a favourite of Samsung and other manufacturers. Perhaps, the demand for devices such as smartphones and the faster product lifecycle due to quicker product iterations and market competition compensate for the aforementioned disadvantages, especially the manufacturing constraints and the shorter lifespan of an AMOLED.
It is also worth mentioning that manufacturers have tried addressing the pressing disadvantages of AMOLED display technology. For example, the iterations made by Samsung on its flagship devices have demonstrated considerable improvements in the performance and lifespan of their respective AMOLED display screens. With progressing technology, it is possible that manufacturers could further improve this display technology.
EDITOR’S NOTE: Several information from the article are culled from the review study “AMOLED: An emerging trend in LED” authored by Vivek Purohit, Tasneem Banu, and Komal Daiya, and published in 2012 in the International Journal of Scientific & Engineering Research. Photo credit: Samsung Electronics/Adapted