Of course, a modern smartphone is one of the most complex electronic devices that uses a large number of complex components. Their technical characteristics directly affect the functionality and, as a result, the choice of the optimal model. This list includes the number and set of cameras in multi-camera smartphones and specs on main camera, smartphone performance and smartphone storage, operation system, etc.
Of course, the display is one of the main components. But its specs, service life and safety for vision depend on the matrix type. All modern TVs and smartphones use AMOLED (Active Matrix Organic Light-Emitting Diode) or LCD screens.
As known, the first light-emitting p-phenylene vinylene (or PPV, or polyphenylene vinylene) polymer was synthesized in the Cavendish Laboratory of the University of Cambridge in 1989. Already in 1992, Cambridge Display Technolodgy (CDT) was established to produce polymer light-emitting materials.
In 2004, Samsung introduced the first X120 phone with an OLED screen.
In August 2008, Nokia introduced the N85 with an AMOLED display.
As known, OLED matrices (Organic light-emitting diode) use multilayer organic polymers that emit light under the influence of an electric current. Accordingly, they do not require backlighting. This factor is their main difference from traditional LCD technology. Today, all companies use OLED matrices with Active Matrix only and are called AMOLED (Active Matrix Organic light-emitting diode). In the TVs segment, companies continue to use OLED abbreviation without adding AM.
Pros & Cons
– perfect black due to lack of backlight provides almost endless contrast (2,000,000: 1 and above);
– large viewing angles eliminate color distortion even when viewing at an angle;
– PWM (pulse-width modulation) provides a wide range of brightness and very accurate color reproduction;
– smaller dimensions and weight;
– instant response due to lack of inertia;
– the ability to create flexible screens;
– wide range of operating temperatures from −40 to +70°C.
– high price;
– screen flicker due to PWM increases eye strain;
– low maximum brightness;
– high sensitivity to moisture;
– slight purple hue due to the eye’s reaction to the blue subpixels.
– the limited service life of the blue phosphor due to its chemical characteristics violates the color balance after several years.
The service life of green diodes reaches 130,000 hours, red – 50,000 hours, blue – only 15,000 hours. Of course, this problem significantly reduces the competitiveness of AMOLED vs LCD.
PenTile, Pixel Shifting and parallax backgrounds
Today, companies use several basic ways to solve this problem.
PenTile (penta + tile) technology integrates a family of proprietary sub-pixel configurations in electronic displays. It was developed in the early 1990s. This method uses the placement in a staggered manner of the five subpixels in each pixel, including two red, two green, and one central blue.
It is based on the characteristics of the retina of the human eye, which contains S (short)-cones, M (medium)-cones and L (long)-cones. Wherein, the number of S-cones significantly exceeds the number of M and L-cones. As known, S-cones provide recognition of blue color. Moreover, blue color almost does not affect the perception of brightness.
In March 2008, Samsung Electronics acquired PenTile from Clairvoyante and funded Nouvoyance, Inc. to continue developing this technology.
Technologically, PenTile adds subpixels to the device matrix. Modern smartphones use RGBG (additional green sub-pixel) or RGBW (additional white sub-pixel).
RGBG provides provides constant brightness while reducing the number of subpixels by 1/3 due to the high perception of green by the human eye. Today AMOLED, Super AMOLED and Super AMOLED HD often use this configuration.
RGBW increases brightness without increasing power consumption and is commonly used in LTPS matrices.
PenTile technology allowed Samsung to use half as many blue and red subpixels compared to green. Moreover, the most powerful blue diodes operate at half power, saving a resource. It increases their service life, and all subpixels burn out evenly.
Pixel Shifting software algorithm shifts the image by 1 pixel for a prolonged static image.
Recently, Google and Apple often use parallax backgrounds, preventing a static image on the screen.
Like LCD, AMOLED matrices use TFT technology. Each pixel uses its own transistor and capacitor for control. AMOLED technology has no size restrictions and is used for 10-inch screens and more.
Super AMOLED is an improved version of AMOLED. They do not have an air gap between the touch layer of the screen and the matrix. In this case, the engineers integrated the sensor layer directly into the screen instead of its surface.
As a result, these screens are thinner, have less power consumption, provide absolute dust protection, a wider saturation of colors and a better image in direct sunlight. Unfortunately, they are more expensive compared to traditional AMOLED screens, and have high image grain due to the use of PenTile RGBG.
A similar technology in IPS matrices is called OGS (One Glass Solution).
Super AMOLED Plus and HD Super AMOLED differ only in the number of sub-pixels and, accordingly, size.
P-OLED matrices use a plastic screen backing instead of a glass. In addition to the traditional pros of OLED technology, this solution provides several additional advantages, including the ability to change the form factor of screens (flexible displays).
Samsung’s latest Dynamic AMOLED version in Galaxy S10 5G is Super AMOLED with HDR10 support.
In addition, they form a less intense blue, which reduces eye strain and increases screen life.
In general, we can state the rapid development of AMOLED technology. Despite the higher price, AMOLED successfully competes with LCD displays, including Retina. Apparently, Samsung will continue to lead in this segment. But its success will significantly depend on the pricing strategy. In comparison, LG, the leader in the OLED TVs segment, has already offered the gorgeous 65-inch LG OLED C9 PUA for less than $ 2,500, which seemed unrealistic just a couple of years ago. It can be assumed that Samsung will also make efforts to lower the price of AMOLED screens.
This video shows a comparison of the iPhone 7+ with Retina LCD Display vs Samsung Galaxy S7 with Super Amoled.