The introduction of LED, OLED and LCD

The introduction of LED, OLED and LCD

Feb 20, 2017


LCD is the full name of the LCD Liquid Crystal Display, mainly TFT, UFB, TFD, STN displayand other types of LCD monitor.

The structure of the LCD is placed in the liquid crystal box two parallel glass substrate, glass substrate is provided under the TFT (thin film transistor), on the glass substrate is arranged on the color filter, rotation direction signal and the voltage change by TFT to control the liquid crystal molecules, so as to achieve the control of each pixel or to exit light to display.This screen is called TFT display.

LCD is a kind of material between solid and liquid, it is not luminous, need to use additional light source. Therefore, the number of lamps is related to the brightness of lcd.

The visual angle of LCD is a headache problem. When the backlight passes through the polarizer, the liquid crystal and the orientation layer, the light output is directional. That is to say, most of the light is emitted from the screen vertically, so from a larger perspective to see the LCD display, they can not see the original color, and even can only see all white or all black.


LED is a light emitting diode Light Emitting Diode. The LED application can be divided into two categories: one is the LED display; two LED single application, including LED backlight, infrared LED. Now on the LED display, with: low power consumption, long service life, low cost, high brightness, less failure, large viewing angle, visual distance and so on.

Principle of LED luminescence and luminescent materials:

The semiconductor material has a very interesting property, is called the carrier; the carrier is divided into two categories: one is the negatively charged electrons,; another kind is the hole, positively charged. LCD light-emitting principle is the use of two kinds of carrier under certain conditions can be combined, the release of energy in the form of a photon from light. It will be in accordance with different materials, electron and hole occupied energy level is different, electron and hole can meet relative height difference is decided on the two carrier with a level of energy, it can generate photons with different energies, which can control the LED light emitted by the wavelength, too is the spectrum or color.

The materials used in LED are mainly 3A-5A element compound semiconductors (e.g. GaP, GaAs, GaN, AlInGaP, etc.). As for why it will emit light of different colors, it is LED itself depends on the materials, such as: red light with AlInGa (arsonium AlGaAs), green GaP (Lin Huajia), blue light with ZnS (zinc sulfide) or GaInN (indium gallium nitride)... Wait

LED can be divided into visible light diode and infrared light emitting diode according to its luminous wavelength. The luminescent principle is the use of electron and hole in a semiconductor integrated, will release energy in the form of a photon from light, and light emitting diode using the material to compound semiconductor 3A, 5A elements, such as: GaAs, GaP, AlGaP, AlInGaP and so on, the emission wavelength and brightness for use the materials vary.

The difference between LCD and LED

Compared with the LCD display, LED has more advantages in terms of brightness, power consumption, visual angle and refresh rate, which has been cancelled to the navigation of the LED. Using LED technology, you can create a thinner, brighter, clearer display than LCD.

1) LED and LCD power consumption ratio of about 1:10, LED more energy.

2) LED has a higher refresh rate, better performance in terms of video performance.

3) LED provides a wide viewing angle of 160 degrees, you can display a variety of text, numbers, color images and animation information, you can play TV, video, VCD, DVD and other color video signals.

4) LED display of a single element reaction speed is 1000 times the LCD LCD screen, can also be taken care of in the light, and to adapt to low temperature of minus 40 degrees.


OLED-- organic light emitting diode

It and LED, though only one letter difference, but in fact the two describe a completely different things. We all know that the LCD panel is through the backlight light, through the refraction of the liquid crystal molecules and produce a variety of different colors, the liquid crystal molecules themselves can not emit light, and LED refers only to the backlight. The OLED itself is able to emit light, so no backlight. LED is used in metal materials, and OLED is the use of organic materials; some more advanced OLED, it does not need light can be self luminous, better contrast, usually with LED, is to have the backlight lamp irradiation can see.



At present, the light emitting diode using materials are inorganic semiconductor materials, are difficult to be applied to large area and requires high-resolution components (EX: screen), to solve these problems depends on the type of organic semiconductor materials (materials containing hydrocarbons), it is coated on a glass sheet conductive, through to current. You can release a variety of different wavelengths of light.

OLED luminescence principle

Organic luminous principle and principle of light emitting diode is similar to that of the same material utilization characteristics, the electron hole in the light emitting layer with electrons from excited state falls back to the ground state, the excess energy is released in the form of wave, and achieve the light function. Therefore, only the OLED and PLED call. OLED is a small molecule organic light emitting diode, PLED is a polymer organic light emitting diode. )

OLED structure

The basic structure of organic light emitting diode as shown below, is to use the same material properties, the electron hole in the light-emitting layer with the electronic excited state by the form back to the ground state, the excess energy in the form of wave release, thus achieving different wavelength light emitting components produced. OLED is used to inject electrons and holes between the two electrodes, and the use of organic molecules to stimulate, and achieve luminous function. The anode is ITO conductive glass film, in the form of evaporation, attached to the glass or transparent plastic substrate, the cathode contains Mg, Al, Li and other metals. In between the two electrodes is the light emitting area of multiple organic thin film formation, including the hole injection zone and hole transfer region, the organic light emitting layer and electron transport layer, in the actual production, considering the different needs of different, sometimes contain other films.

OLED color mode

The organic light emitting diode to green technology is the most mature, blue light and red light to be commercialized. Color organic light emitting diode display is divided into monochrome, color and color, colorful, is composed of a plurality of monochrome display areas, each area is composed of repeated full-color monochrome; pixel red, green and blue three colors, the pixel size is fine, the higher the resolution. In display applications, color is the necessity of success in market.

What are the advantages of OLED technology?

OLED is an organic light emitting diode, also known as laser display with light, electrical power and other characteristics, so from the beginning of 2003, the display device has been widely used in a MP3 player, and for DC and mobile phone are digital products, previously only in some exhibition shows the OLED screen project samples. Not into the practical application stage. But the OLED screen has many incomparable advantages of LCD, so it has been optimistic about the industry.

OLED application

OLED are mainly used in vehicle type displays, mobile phones, game consoles, handheld portable mini computer, personal digital assistant (PDA), car audio and digital camera... Etc.. The future will be towards the high efficiency fluorescent material development, 5 inch full-color display production, the organic components of new application development, high resolution full-color display the development of small size, such as intelligent mobile telephone.

In the current liquid crystal display technology, OLED has many advantages, such as ultra-thin, good seismic performance, large viewing angle, short response time, low temperature, high luminous efficiency and so on. It should be noted that, although OLED has gradually been well known, but now we do not see a large area of OLED products listed.