A modern smartphone uses a large number of complex components, including main camera and several additional cameras in multi-camera smartphones, chipset, RAM and ROM, operation system, etc. Their specs directly affect the functionality and, as a result, the choice of the optimal model.
But of course, the display is one of the main components. 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, before the invention of OLED technology, LED LCD displays dominated the market. 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.
But the fierce competition between them began only in the 21st century, provoking their rapid development.
LCD
As known, LCD (Liquid Crystal Display) technology uses fluidity and anisotropy of crystals. In fact, they perform the function of a light filter, forming a pixel of the desired color on the screen surface. Of course, this technology requires a backlight that uses LEDs.
In February 2011, Samsung introduced the first QLED display with improved LED backlighting on quantum dots. In fact, engineers added an LED panel instead of traditional cold cathode fluorescent tubes.
This technology has significantly expanded the color gamut of the matrix. Further, other companies developed their own technologies based on this idea. Today they use their own marketing names, including NanoCell from LG, Triluminos from Sony and ULED from Hisense.
In parallel, companies developed backlight technology. As a result, FALD (full-array local dimming) backlighting was developed.
Today, experts expect LCD with innovative miniLED-based backlighting. Unlike traditional backlighting, the size of its diode modules does not exceed 100 microns.
The reduction in size promises to drastically reduce energy consumption, increase contrast and color accuracy by increasing the number of local dimming zones. TVs already use this technology.
For example, TCL announced 8-series MiniLED Roku TV with 1,000 local dimming zones. In comparison, today the best expensive LCD TVs use no more than a few hundred. This technology promises to bring the quality of LCD screens closer to AMOLED. Some experts were expecting these smartphones in 2019. Unfortunately, their hopes did not materialize.
OLED
OLED matrices (Organic light-emitting diode) use multilayer organic polymers that emit light under the influence of electricity and do not require backlighting. In fact, it’s the main difference between these technologies. All modern phones use only AMOLED (Active Matrix OLED) matrices with Active Matrix. But in the TV segment, companies continue to use the acronym OLED without adding AM.
In the summer of 2009, LG announced the first 15-inch OLED TV. A few years later, at CES 2012, Samsung and LG introduced 55-inch OLED TVs. At IFA 2013, LG has already announced the world’s first 77-inch 4K OLED TV.
At CES 2013, Samsung announced the Galaxy S4 with 5 “Super AMOLED Full HD panel. In the second half of 2014, Samsung Display began production of AMOLED flexible panels.
Modern models already use AMOLED, Super AMOLED, HD Super AMOLED, Dynamic AMOLED and P-OLED matrices.
MicroLED (mLED or μLED or ILED)
MicroLED is the next step in the development of OLED technology. Like OLED, MicroLED uses subpixel LEDs with its own radiation and does not require backlighting. But as a light-emitting material, OLED uses sm-OLED (Small Molecule-Organic LED), POLED, or PHOLED (phosphorescent OLED). MicroLED uses inorganic GaN (gallium nitride) with a size of only 5-10 microns, which is its main advantage.
The new technology has great prospects. In particular, high light output can drastically reduce energy consumption to about 10% LCD and 50% OLED displays, and the miniature size will allow companies to achieve pixel densities of up to 1,500 PPI, providing huge resolution even for large matrices.
In 2018, Apple announced plans to produce MicroLED panels. But in 2019, serial microLED displays did not appear on the market. However, Sony and Samsung are already selling microLED The Wall.
OLED advantages
1. As known, contrast characterizes the ratio brightest white to the darkest black pixels on the screen and is measured in the ratio of “maximum brightness” / 1. Thus, a screen with a contrast ratio of 1000: 1 displays white 1000 times brighter than black.
But in the OLED display, black color corresponds to a completely off diode with a brightness of “0”. Therefore, companies often use the term “Infinite contrast”, although, as you know, mathematics prohibits the division by “0”. Sometimes companies indicate 2,000,000: 1 and above, which is probably more correct.
Unfortunately, LED backlight in the LCD screen fundamentally eliminates the perfect black.
2. Smartphones with OLED screens support Always On-Display mode. In this case, the smartphone’s display can display information by controlling individual pixels. This mode provides a significant reduction in energy consumption when choosing interface in dark colors.
But black color of the IPS matrix corresponds to the on backlight, which we do not see due to the light wave damping by the second polarizer. Thus, the IPS matrix cannot provide this useful option because its backlight constantly illuminates the matrix.
3. As known, the image brightness decreases when viewed at an angle. For example, the brightness drop in smartphones with IPS-screen reaches 55% for an angle of 30 degrees. For comparison, brightness reduction of the OLED screen at the same angle does not exceed 25%.
4. The absence of a backlight in OLED screen eliminates problems with its uniformity. Unfortunately, it’s relevant for the IPS screen. Typically, companies place backlight diodes along the bottom edge of the IPS screen. During operation, their light passes through a special flexible diffuser made of a thin film. Unfortunately, many LCD screens display a brighter bar at the bottom of the screen near the diodes.
LCD advantages
1. IPS-screen is much cheaper than OLED-analogue, including repair.
2. Almost all OLED screens have problems with Screen burn-in.
The service life of green diodes reaches 130,000 hours, red – 50,000 hours, blue – only 15,000 hours.
However, today companies successfully solve this problem using PenTile. For example, 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. Typically, companies use RGBG (additional green sub-pixel) or RGBW (additional white sub-pixel).
Today AMOLED, Super AMOLED and HD Super AMOLED often use this configuration.
On the other hand, 15,000 hours of service life for blue diodes corresponds to more than 5 years of operation, even with heavy use. Most people change models more often.
In addition, static displaying for a long time at maximum brightness may form a residual image on the screen. But Pixel Shifting and Parallax Backgrounds successfully solve this problem.
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.
3. Screen flicker due to PWM in OLED screen increases eye strain. As known, the diode brightness depends on the current strength. With its increase, it gradually rises. Unfortunately, the decrease in brightness does not occur smoothly. Instead of smooth dimming, the diodes begin to work with small pauses. For example, diodes burn 0.9 ms for 1 second at 100% brightness. But at 50% brightness, these LEDs only work for 0.45 ms for 1 second. Of course, this flicker significantly increases the load on the eyesight, causing discomfort in the eyes.
Brands
Today, budget and mid-budget Android, and Apple, mainly use LCD displays. This list includes:
– iPhone 11;
– iPhone XR;
– Honor 20/20 Pro;
– iPhone 8/8 Plus, iPhone 7/7 Plus;
– Xiaomi Redmi Note 7;
– Huawei P30 Lite.
AMOLED screens are used on almost all flagships and even on mid-range smartphones. This list includes:
– the entire line of Samsung Galaxy S-series, Note-series, etc;
– iPhone 11 Pro / 11 Pro Max, iPhone XS / XS Max and iPhone X;
– Huawei flagships (P30, Mate 30);
– Xiaomi flagships (the entire line of Mi 9, etc.);
– Sony Xperia XZ3 and Xperia 1.
Conclusion
In general, the trend clearly demonstrates the rapid convergence of technology. The active use of effective innovative technologies has ensured the convergence of consumer qualities of models with AMOLED and LCD matrices. Of course, AMOLED retains a slight advantage in image quality, but LCD successfully compensates for it due to price.
Today we can assume the direction of their further improvement. Apparently, the market will soon offer LCD screens with miniLED-based backlighting. In the segment of OLED technology, MicroLED displays have good prospects over time to replace modern AMOLED screens. In this case, LCD with miniLED will compete with MicroLED in the next step.
This video shows the 75-inch and 219-inch Samsung Micro LED Modular TVs at CES 2019.
