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When shopping for gadgets, one of the biggest factors for many of us will be the screen. From immersive, curved widescreen computer monitors to the tiny screen on an Apple Watch, a good display needs to make everything look bright, beautiful and sharp. To arm you with better knowledge before your make your next big purchase, today we’re taking a close look at the two main types of displays that are available on most consumer electronic devices today, OLED and LCD.
What is an LCD display?
LCD stands for liquid crystal display. It’s named for the thin layer of liquid crystals that forms the main mechanism of the display. This is sandwiched between two layers of transparent electrodes on glass plates, which are themselves placed between two polarizers. These polarize light, which then passes through the crystal layer, causing the crystals to adjust their angles and either reveal or block the light.
The light that isn’t blocked passes through a layer of blue, red and green filters, which are modulated by the electrodes on top to create the color of each pixel. Because an LCD itself cannot produce light, an external backlight, usually an LED or CCFL (Cold Cathode Fluorescent Lamp), is placed at the bottom of these layers to illuminate the display.
As an older technology, many different kinds of LCD displays have been developed over the years. We all know the monochrome LCD displays from classic calculators and digital watches, with this basic technology first used in the 1970s and known as passive matrix LCD. Yet most the LCD displays we use today are one of the many types of active matrix displays, including twisted nematic LCDs favored by gamers for their price and quick refresh rate, and high-end in-plane switching LCDs used by graphic designers because of their excellent color precision.
What is an OLED display?
OLED stands for Organic Light Emitting Diode. This is essentially based on regular LED technology, where each pixel is actually a tiny diode that can illuminate blue, green or red in a way that creates an image when seen from afar. LEDs had been used to create displays with varying success since the 1990s but had drawbacks like slow refresh rates and limited viewing angles. OLED was developed to address these problems by using organic molecules instead of the junction diodes of LEDs.
A layer of organic (carbon-based) film is placed between two conductors so it lights up whenever an electrical current is passed through. Tiny red, green and blue filters are then added to each pixel so that the light that shines through to create the desired image. It was the invention of OLED that made use of LEDs possible in TV and smartphone screens.
OLED technology has also received a few updates, the biggest of which is AMOLED, or active-matrix organic light-emitting diodes. In AMOLED technology, a thin film transistor and capacitor (the active matrix) are attached to each LED. These store energy in order to more quickly and precisely control how pixels are changed, which provides a faster refresh rate and greater power efficiency. There’s now even Super AMOLED, which is used in the latest smartphones like the Samsung Galaxy F41.
Main differences between OLED and LCD screens
So, what exactly does all this mean in practical terms? Although they’re designed for the same function, the different technologies used in OLED and LCD ensure each has its own pros and cons.
The way LCD and OLED screens render color is different. The crystals in LCD screens rotate to block white light from the backlight in a particular pixel area, but don’t technically control the color on a pixel-by-pixel basis. On the other hand, the pixels in OLED screens are illuminated independently, which offers a greater level of accuracy and control. This means that OLED generally have truer colors, better contrast, and higher brightness.
At the same time, because black is created by turning the pixel off completely, OLEDs can display a truly deep black when compared to LCDs, which block white light from the backlight to create black. LCDs do, however, display a brighter white than OLEDs because of their backlight.
LCD and OLED technologies also use energy in different ways. Because OLEDs use power to illuminate pixels, their power consumption is directly related to what is being displayed: they need more energy to display bright images because more of the pixels are turned on. However, more pixels are turned off when darker images are displayed, using less energy. This is why it’s considered more economical to use the dark themes in smartphone apps.
The energy consumption of LCD displays, however, is related to the screen brightness itself. They require constant power to illuminate the backlight, regardless of how bright or dark the images being displayed are. This means that keeping a screen’s brightness level lower can conserve more energy.
The organic elements inside OLEDs give them an inherently shorter lifespan than LCDs, because the materials degrade over time. While generally rare when considering the relatively short lifespans of electronic devices, OLED displays can suffer from color degradation and burn-in. Blue LEDs tend to degrade faster than red or green, which means that areas of a screen that tend to display blue or white for long periods of time will tend to wear out and appear as burn-in.
Modern LCD technology uses inorganic materials, so it generally remains in good condition longer without experiencing the same kind of color degradation as OLEDs. When the crystals don’t return to their relaxed state the screens can develop a type of burn-in called image persistence, but this is just temporary and can usually be fixed by turning the screen off overnight.
Both physically and conceptually speaking, OLED technology is flexible. Compared to LCD, OLED displays are incredibly thin, and the organic film and other components can be mounted to a flexible substrate (usually a polymer or plastic) to take on a curved shape or even bend. OLEDs even make possible foldable screens, which some see as the future of smartphones.
OLEDs are also flexible in the sense that they can be used in a variety of unique ways. Recent developments include printable OLEDs and even OLED tattoos, both of which show promise for innovative and useful applications in the future.
As we’ve seen, each type of display as its own merits, and the best type of screen may depend on what it’s for, and how you use it. Each of these technologies is being constantly innovated and advanced, so it will be exciting to see what kind of developments happen in the near future.