A pixel on a modern display is made of tiny colored light elements called subpixels, typically three per pixel, arranged as red, green, and blue. But the physical materials behind those subpixels depend entirely on the type of screen. An LCD pixel is built from liquid crystals, color filter pigments, and transparent electrodes sandwiched between glass. An OLED pixel uses layers of organic carbon-based compounds that emit light directly. Each pixel is smaller than you might expect: on a high-end smartphone, a single pixel can measure less than 30 micrometers across, roughly a third the width of a human hair.
The Basic Structure: Three Subpixels Per Pixel
Every color pixel on a screen is actually a cluster of smaller elements. The standard arrangement places a red, green, and blue subpixel side by side from left to right. By mixing these three colors at different brightness levels, a single pixel can produce millions of visible colors. White appears when all three subpixels glow at full intensity. Black appears when all three are off.
Some displays use alternative layouts. A few panels arrange subpixels in triangles or reverse the order to blue, green, red. Others add a fourth white subpixel (RGBW) to boost brightness and energy efficiency. But the RGB trio remains the dominant design across phones, monitors, and televisions.
What LCD Pixels Are Made Of
LCD pixels don’t generate their own light. Instead, they act as tiny shutters that control how much light from a backlight passes through. The physical stack of materials in a single LCD pixel includes several distinct layers.
At the core are liquid crystals, rod-shaped molecules that twist or untwist when voltage is applied. This twisting controls how much light can pass through. On either side of the liquid crystal layer sit polarizing filters that block light traveling in certain directions. The combination of these polarizers and the liquid crystal’s orientation determines whether a subpixel appears bright or dark.
To create color, a thin color filter layer sits on top. Red subpixels use pigments like dianthraquinone red. Blue and green subpixels use copper phthalocyanine pigments. These chemical dyes, which include compounds with carboxyl, amino, or sulfone groups, are dispersed into light-sensitive polymers and patterned onto the glass during manufacturing.
The electrodes that deliver voltage to each pixel are made of indium tin oxide (ITO), a material that conducts electricity while remaining transparent. ITO films transmit about 91% of visible light, which is why you can see through them to the backlight behind. Each pixel also has its own tiny transistor, a thin-film transistor (TFT), that acts as a switch to control voltage. These transistors are made from materials like amorphous silicon or newer compounds like indium gallium zinc oxide (IGZO), which allow faster switching and lower power consumption.
What OLED Pixels Are Made Of
OLED pixels work on a fundamentally different principle. Each subpixel contains a thin layer of organic (carbon-based) semiconductor material sandwiched between two electrodes. When electricity flows through, it pushes positive and negative charges into the organic layer from opposite sides. These charges meet, pair up into bundles of energy called excitons, and then release that energy as visible light.
The organic compounds used in OLEDs vary widely. Researchers first demonstrated the effect using anthracene crystals back in 1963, but modern OLEDs use a broad family of specially engineered molecules. Some are small molecules, others are longer polymer chains. There is a nearly unlimited number of chemical compounds that can serve as the light-emitting layer, which is what allows manufacturers to tune each subpixel to produce a precise shade of red, green, or blue.
Because each OLED subpixel generates its own light, there’s no need for a backlight or color filter. This is why OLED screens can display true black (the pixel simply turns off) and why they can be made thinner and even flexible.
Quantum Dots: A Newer Pixel Material
Quantum dot displays, marketed under names like QLED, introduce nanometer-scale crystals into the pixel structure. These tiny semiconductor particles have a useful property: the color of light they emit depends on their physical size. Smaller dots produce blue light, larger ones produce red, with green in between.
In most current TVs, quantum dots work as color converters. A blue LED backlight shines through a layer of quantum dots, which absorb the blue light and re-emit it as highly pure red or green. This approach produces a wider range of colors than traditional LCD color filters alone, with emission efficiency gains of 23% for red and 32% for green compared to setups without quantum dots.
The next generation of quantum dot displays aims to make each pixel emit light directly, similar to how OLEDs work. In these electroluminescent quantum dot pixels, electrical current drives the dots to produce photons without needing a separate backlight. This technology is still maturing, partly because the surface chemistry of the nanocrystals can degrade at higher temperatures, causing defects that reduce lifespan.
How Pixels Are Physically Built
Manufacturing pixels at modern densities requires extreme precision. The primary technique is photolithography, the same process used to make computer chips. A light-sensitive coating is spread across a glass or silicon substrate, then exposed to ultraviolet light through a patterned mask. The UV light hardens certain areas while leaving others soft enough to wash away, creating the microscopic structures needed for each pixel.
For quantum dot displays, researchers have achieved resolutions up to 6,350 pixels per inch using photolithographic templates, with individual pixels as small as 2 micrometers on a side. Other manufacturing methods include inkjet printing, where tiny droplets of light-emitting material are deposited directly onto the substrate, and transfer printing, where pre-made pixel structures are lifted from one surface and placed onto another.
Transparent electrode layers like ITO are deposited through sputtering, a process that knocks atoms off a target material and onto the substrate in an ultra-thin, even film. Each additional layer in the pixel stack, whether it’s a hole-transport layer, the emissive material, or an electron-transport layer, is applied through spin-coating or vacuum deposition, then baked at precise temperatures to set its structure.
Camera Pixels Work Differently
Pixels in a camera sensor are built to capture light rather than produce it. Each pixel on a CMOS image sensor contains a photodiode, a tiny piece of silicon that converts incoming photons into an electrical charge. The more light that hits the photodiode, the stronger the signal, which translates to a brighter pixel in the final image.
Sitting on top of each photodiode is a microlens, a curved piece of glass or polymer that focuses incoming light onto the active area so less of it goes to waste. Above that is a color filter. Most camera sensors use a Bayer filter array, a repeating grid of red, green, and blue filters (with twice as many green filters as red or blue, since human vision is most sensitive to green). Each pixel only captures one color, and the camera’s processor combines neighboring pixels to reconstruct the full-color image.
How Small Pixels Have Gotten
Pixel size has shrunk dramatically over the past two decades. Around the year 2000, a typical computer monitor had a pixel density of 67 to 130 pixels per inch, meaning each pixel was roughly 200 to 380 micrometers wide. Today’s desktop monitors commonly exceed 200 PPI, and flagship smartphones have surpassed 500 PPI since 2014. Sony’s Xperia XZ Premium pushed smartphone density to 807 PPI with a 4K display, where each pixel measures only about 31 micrometers across.
At the extreme end, specialized displays for virtual reality headsets and microdisplays have reached over 2,000 PPI, with pixels as small as 11 micrometers. Spatial light modulators used in research settings can achieve 10,160 PPI with a pixel pitch of just 2.5 micrometers. At that scale, you’d need a microscope to see a single pixel.