LCD display VS LED display

LCD display VS LED display are both common display products in daily life. Many people see that the two look alike, so they are often confused. So do you know the difference between the two? Let’s learn together.

One of the main differences between LEDs and LCDs is that LEDs use PN junction diodes that emit light when current is passed through them, while LCDs use liquid crystals or plasma to emit visible light. Liquid crystal is filled between the glass electrodes, and when power is applied to it, the liquid crystal becomes energized and emits light.

Tips: What is a PN node

p-n node

When a p-type semiconductor is connected to an n-type semiconductor, the contact thus formed is called a p-n junction. All semiconductor devices contain one or more PN junctions. The p-n junction is actually the control element of the semiconductor device.

Formation of p-n junction

In practical applications, a PN junction is not formed simply by placing a p-type semiconductor block close to an n-type semiconductor block. In fact, p-n junctions are fabricated by special techniques, namely growth, alloying and diffusion methods.

p-n junctio fig
p-n junctio fig

The most common method of making pn junctions is called alloying. Alloy junctions are made of n-type semiconductors made of germanium or silicon by melting trivalent indium particles placed on either side. The entire arrangement or system is heated to about 500 degrees Celsius. Indium is absorbed into germanium or silicon to create a p-region, thus forming a pn junction.

Another method of forming a pn junction is called diffusion. In this process, a semiconductor wafer p-type or n-type with one conductivity is placed in a container containing the impurity oxide to be added. The combination is slowly passed through a furnace controlled at a temperature of 800⁰C to 1200⁰C, depending on the type of junction. At such high temperatures, a gas of impurity atoms diffuses into the semiconductor material, forming a thin layer of opposite conductivity. Therefore, a pn junction is formed.

Either LED or LCD, both can be used to display images and text. But the chemistry is not the same. LEDs use gallium arsenide and gallium phosphide, two compounds that emit visible light when heated.

p-n junctio fig
p-n junctio fig

When the monochromatic light is displayed, it is usually used to display basic elements such as numbers and letters or some specific symbols. When there is only monochromatic light, it is still unable to display the picture or more complex patterns and other elements normally.

LCD, on the other hand, is a thin layer of liquid crystal filaments between glass electrodes. When power is applied to the electrodes, they begin to emit light energy in the form of photons. Therefore, the LCD can directly display text or images in the form of dot matrix and line segments.

Definition of LED

The complete form of LED is light-emitting diode, so light-emitting diode is the abbreviation of LED. An LED is a PN junction diode that emits light when current flows forward. LEDs are constructed by doping p-type and n-type materials. When power is applied to the LED, the P-type and N-type material charges will chemically react, the charges will recombine, and provide energy in the form of heat and light.

brightness contrast
brightness contrast

The material of semiconductors is translucent (allowing light to pass through) and it emits light through their junctions. The semiconductor material uses zinc arsenic compounds, which can produce red or yellow light. It is also available in green, red and amber colors.

When multiple LED displays are combined together, the distance from one of the lights to the other is measured. This distance is generally represented by the capital letter “P”. For example, the P2 LED display is the LED light to the other LED light. The distance is 2 mm.

Definition of LCD screen

LCDs are used to display text and images in the form of dots or line segments. LCDs have liquid crystal filaments that are filled between transparent electrodes. When current is passed between the electrodes, the filament becomes energized and emits visible light.

Liquid crystals used in displays have both solid and liquid properties. When no potential is applied to the liquid crystal, it becomes transparent, but upon activation, the crystal scatters light in all directions and appears bright.

light crystal diode
light crystal diode

The LCD power consumption is very low and it also has a seven segment display. But it is equivalent to an LED, which is a slower device and takes more time to switch. DC shortens their lifespan, so they are mostly used with AC at frequencies below 500 Hz.

The main difference between LED and LCD

  • An LED is a PN junction diode that emits visible light when forward bias is applied to it. LCDs use liquid filaments that are filled between glass electrodes to emit light.
  • LED stands for Light Emitting Diode while LCD stands for Liquid Crystal Display
  • LCDs use cold cathode fluorescent lamps to provide backlighting for the screen, and LEDs use PN junction diodes to display light. Backlighting refers to turning the display on and off for better viewing.
  • The scalability of LED is very strong, so the resolution is much better than LCD, and it is easy to implement, so many 4K and 8K displays are being converted from LCD to LED. Resolution is the number of pixels on the screen display.
  • Due to the plasma, LEDs consume more power compared to LCDs. Filaments used in LCDs consist of plasma, which requires less power to activate.
  • LEDs have a smaller display area compared to LCDs because LEDs use PN junction diodes that display light in only one direction, while LCD displays light up in all directions. However, after the LED is made into an LED display, it can be spliced ​​in an infinite area, while the LCD can only be made according to the specified size, and cannot be spliced ​​in an infinite area.
  • Compared with LCD, to achieve the same picture effect, the cost of LED is higher.
  • LEDs use gallium arsenide, which emits light when heated, while LCDs use liquid crystals that energize and provide light.
  • LEDs have shorter switching times compared to LCDs. Toggle times are their displayed activation and deactivation times.
  • DC will shorten the lifespan of LCDs, while LEDs have no effect.
  • Compared to LCD, LED has lower contrast ratio. Contrast ratio is the ratio of the brightness of the visible light to the darker light on the screen.
  • LCDs use mercury that pollutes the environment, while LEDs do not.

in conclusion:Both LED and LCD are modern technologies. Neither is the strongest, only which is more suitable.