Popular science: What is the difference between OLED and LED?

Everyone must see the term "LED" frequently. It has only one letter difference with OLED, but in fact, the two describe completely different things. We all know that liquid crystal panels emit light through a backlight, and various kinds of colors are produced by the refraction of liquid crystal molecules. Liquid crystal molecules cannot emit light by themselves, and LEDs only refer to backlights. The OLED itself emits light, so no backlight is needed. LEDs are made of metal materials, while OLEDs are made of organic materials. OLEDs are more advanced. They can emit light without illumination, and the contrast is better. Usually, LEDs must have backlights to see things.

First, LED lighting principle and luminescent materials

Semiconductor materials have a very interesting property, the so-called carriers; carriers are divided into two categories: one is electrons, with negative electricity; the other is holes, with positive electricity. The principle of illumination of an LCD is that it can be combined under certain conditions by using two kinds of carriers, and the released energy is emitted in the form of photons to emit light. It depends on the material, the energy level occupied by electrons and holes is different, that is to say, the relative height difference between electrons and holes is the difference between the energy of the two carriers, which can produce different energy. The photon, by which the wavelength of the light emitted by the LED, that is, the spectrum or color, can be controlled.

The material used for the LED is mainly a 3A-5A element compound semiconductor (such as GaP, GaAs, GaN, AlInGaP, etc.). As for why it emits different colors of light, it depends on the material of the LED itself. For example, red light uses AlInGa (deuterated aluminum gallium), green light uses GaP (gallium phosphide), and blue light is used. ZnS (zinc sulfide) or GaInN (gallium indium nitride)...etc.

LEDs are distinguished by their wavelengths of light emission and can be broadly classified into visible light diodes and infrared light emitting diodes. The principle of light emission is that when the electrons in the semiconductor are combined with the holes, the released energy is emitted in the form of photons, and the materials used in the light-emitting diodes are mainly compound semiconductors of the 3A and 5A elements, such as GaAs. GaP, AlGaP, AlInGaP, etc., the wavelength and brightness of the light will vary depending on the materials used.

Second, OLED--organic light-emitting diode

At present, the materials used in light-emitting diodes are inorganic semiconductor materials, which are difficult to apply to large-area components and require high-resolution components (EX: screen). To solve these problems, it is necessary to use new organic semiconductor materials (ie, hydrocarbon-containing compounds). Material), it is coated on a conductive glass sheet, and current can be used to emit light of various wavelengths.

1, OLED lighting principle

The principle of organic light emission is similar to that of light-emitting diodes. The material properties are also used to combine the electron holes on the light-emitting layer. The electrons are returned to the ground state from the excited state, and the excess energy is released in the form of waves to achieve the function of light emission. Therefore, there are OLED and PLED names. (OLED is a small molecule organic electroluminescent diode, PLED is a polymer organic electroluminescent diode.)

2, OLED structure

The basic structure of the organic light-emitting diode is shown in the figure below. It also uses the characteristics of the material to combine the electron holes on the light-emitting layer, and the electrons are returned from the excited state to the ground state, and the excess energy is in the form of waves. Released, thus achieving the production of illuminating components having different wavelengths. OLEDs use the function of injecting electrons and holes between two electrodes and using the excitation of organic molecules to achieve luminescence. The anode is an ITO conductive glass film, which is deposited on a glass or a transparent plastic substrate by vapor deposition, and the cathode contains a metal such as Mg, Al or Li. Between the two electrodes is a light-emitting region formed by a plurality of organic thin films, including a hole injection region, a hole transfer region, an organic light-emitting layer, and an electron transport layer. In actual mass production, different needs are considered, and sometimes other components are included. Different films.

3, OLED colorization

At present, the technology of organic light-emitting diodes with green light is the most mature, and blue light and red light are still to be commercialized. The color of the OLED display is divided into monochrome, colorful and full color. The color is composed of several monochrome display areas, each area is still monochrome; the full color is a repeating pixel of red, green and blue light. Composition, the finer the size of the pixel, the higher the resolution. In the application of the display, full color is a necessary condition for market success.

4. What are the advantages of OLED technology?

OLED is an organic light-emitting diode, also known as organic electro-laser display. Because of its characteristics of lightness and power saving, since 2003, this display device has been widely used in MP3 players, and DC for the same digital products. With mobile phones, engineering samples using OLED screens have only been shown at some exhibitions, and have not yet entered the stage of practical application. But OLED screens have many advantages that LCDs can't match, so it has always been favored by the industry.

5, OLED application

At present, OLED is mainly used in automotive displays, mobile phones, game consoles, handheld portable small computers, personal digital assistants (PDAs), car audio and digital cameras. In the future, we will develop high-fluorescence-efficient materials, the production of 5-inch full-color displays, the development of new applications for organic components, and the development of high-resolution full-color small-sized displays, such as smart mobile phones.

In the current liquid crystal display technology, OLED has many advantages such as ultra-thin, good seismic performance, large viewing angle, short response time, good low temperature, and high luminous efficiency. It should be noted that although OLEDs have gradually become known, we have not seen a large number of OLED products on the market.