PM-OLED technology
PM-OLED technology
PM-OLED (Passive Matrix Organic Light-EmitTIng Diodes), with self-luminous, thin and light, high response speed, wide viewing angle, low driving voltage, wide operating temperature range and other characteristics, suitable for automotive displays and the consumption of volume, audio and video functions Sex electronics. However, insufficient luminous efficiency, incomparable product lifespan compared with mainstream LCDs, and immature mass production technologies are all problems that PM-OLED manufacturers need to overcome. This article will discuss the current development of PM-OLED technology.
Preface Organic Light Emitting Diode (Organic Light EmitTIng Diode; OLED), or organic electroluminescent display (Organic Electroluminescent Display; OELD) is a self-luminous display.
Depending on the organic thin-film material used, organic light-emitting diodes can be divided into small molecules (Small Molecular; molecular weight less than 1,000) and polymers (Polymer; molecular weight greater than 10,000).
In addition, the driving method can be classified into passive matrix (Passive Matrix) and active matrix (AcTIve Matrix). The research scope of this article is the development status of small molecule passive organic light emitting diode (Passive Matrix Organic Light EmitTIng Diode; PM-OLED).
Commercialization Process In 1997, Pioneer released a car stereo with a monochrome PM-OLED panel with a resolution of 256x64; in 1999, Tohoku Pioneer successfully developed a 5.2-inch, 320x240 pixels, 256-color full color (Full color) PM-OLED panel; Motorola mobile phone "Timeport" uses Tohoku Pioneer's 1.8-inch area color PM-OLED panel in 2000; Samsung launched a mobile phone with full-color PM-OLED panel in 2001; Fujitsu mobile phone F505i in 2002 The secondary screen is paired with Tohoku Pioneer's 1.0-inch full-color PM-OLED panel. Since then, the application of PM-OLED in mobile phone secondary screens has risen in great numbers.
In the following, we will briefly discuss the current development of PM-OLED technology in terms of the basic structure, operating principle, organic light-emitting materials and full-color display technology of PM-OLED.
Current status of PM-OLED technology development:
The basic structure of a typical PM-OLED is composed of a glass substrate, ITO (indium tin oxide; indium tin oxide) anode (Anode), organic light-emitting layer (Emitting Material Layer) and cathode (Cathode), etc., of which, thin and transparent The ITO anode and the metal cathode sandwich the organic light-emitting layer like a sandwich. When the voltage injected into the anode hole (Hole) and the electrons (Electron) from the cathode combine in the organic light-emitting layer, the organic material is excited to emit light.
At present, the multi-layer PM-OLED structure with better luminous efficiency and commonly used, in addition to the glass substrate, the cathode electrode and the organic light-emitting layer, it is necessary to fabricate a hole injection layer (HIL) and a hole transmission layer (HIL) Hole Transport Layer (HTL), Electron Transport Layer (ETL) and Electron Inject Layer (EIL) and other structures, and an insulation layer is required between each transport layer and the electrode, so thermal evaporation (Evaporate) ) The processing difficulty is relatively increased, and the production process is also complicated.
Since organic materials and metals are quite sensitive to oxygen and moisture, after the production is completed, they need to be protected by packaging. Although the PM-OLED needs to be composed of several organic thin films, the thickness of the organic thin film layer is only about 1,000 ～ 1,500A ° (0.10 ～ 0.15 um), and the total thickness of the entire display panel (Panel) is less than 200um after encapsulation and desiccant (Desiccant) (2mm), with the advantage of thinness.
Principle of operation Organic light-emitting diodes are similar to inorganic light-emitting diodes. When the component is forward biased by direct current (DC), the applied voltage energy will drive the electron (Electron) and hole (Hole) into the component from the cathode and anode respectively, when the two meet in conduction , Combination, that is, the so-called Electron-Hole Capture (Electron-Hole Capture). When a chemical molecule is excited by external energy, if the electron spin (Electron Spin) and the ground state electron are paired, it is a singlet (Singlet), and the light released is the so-called fluorescence (Fluorescence); otherwise, if Excited state electrons and ground state electron spins are not paired and parallel, which is called the triplet state (Triplet), and the light released is so-called phosphorescence (Phosphorescence).
When the state position of the electron returns from the excited high energy level to the stable low energy level, its energy will be released in the form of photon (Light Emission) or heat energy (Heat Dissipation), and the part of the photon can be used as a display function; However, organic fluorescent materials cannot observe triplet phosphorescence at room temperature, so the theoretical limit of the luminous efficiency of PM-OLED devices is only 25%.
The principle of PM-OLED luminescence is to use the energy difference of materials to convert the released energy into photons, so we can choose the appropriate material as the luminescent layer or dope the luminescent layer with dye to get the luminous color we need. In addition, the combination reaction of electrons and holes is generally within tens of nanoseconds (ns), so the response speed of PM-OLED is very fast.
Organic light-emitting materials The characteristics of organic materials deeply affect the performance of the device's photoelectric properties. In the choice of anode material, the material itself must have a high work function (High work function) and light transmittance, so it has a high work function of 4.5eV-5.3eV, stable properties and transparent ITO transparent conductive film, It is widely used in anodes. In the cathode part, in order to increase the luminous efficiency of the device, the injection of electrons and holes usually requires low work function (Low work function) metals such as Ag, Al, Ca, In, Li, and Mg, or composite metals with low work function. Make cathode (for example: Mg-Ag magnesium silver).
Organic materials suitable for transferring electrons are not necessarily suitable for transferring holes, so the electron transport layer and the hole transport layer of the organic light-emitting diode must use different organic materials. At present, the most commonly used material for the electron transport layer must have high stability, thermal stability, and good electron transportability. Generally, fluorescent dye compounds are generally used. Such as Alq, Znq, Gaq, Bebq, Balq, DPVBi, ZnSPB, PBD, OXD, BBOT and so on. The material of the hole transport layer belongs to an aromatic amine fluorescent compound, such as organic materials such as TPD and TDATA.
The material of the organic light-emitting layer must have the characteristics of strong fluorescence in the solid state, good carrier transmission performance, good thermal and chemical stability, high quantum efficiency and vacuum evaporation. The materials used for the electron transport layer or the hole transport layer are the same. For example, Alq is widely used for green light, and Balq and DPVBi are widely used for blue light.
P-OLED microdisplays will soon be put into commercial R & D and production of the smallest P-OLED screen of the King ’s Record Micr oEmissive Displays (MED) company. The first consumer electronics product will be launched by the Japanese digital camera factory NHJ in the middle of this year, combined with recording and playback MP3 And high-resolution digital camera, MED's ME3203 is a low-power 1/4 VGA resolution (3 20 x RGB x 240) P-OLED microdisplay (Microdis play), which will be used in the electronic viewfinder and eyepiece of new products on. It is understood that this new global product was designed and developed by a digital camera factory in Taiwan.
MED strategy Ian Underwood said that for the commercialization of microdisplay technology, MED has invested five years, and it has now matured and achieved a world-class unique technology level.
Prospects for the development of PM-OLED OLED is a flat panel display technology with great development prospects, it has very excellent display performance, especially self-luminous, simple structure, ultra-thin, fast response, wide viewing angle, low power consumption and achievable Features such as flexible display are known as "dream displays". In addition, their production equipment investment is much smaller than TFT-LCD, which has been favored by major display manufacturers and has become the main force of the third generation of display devices in the field of display technology.
At present, OLED is on the eve of mass production. It can be believed that with the further research and the continuous emergence of new technologies, OLED display devices will surely have a breakthrough development.
Insulated Power Cable,Bimetallic Crimp Lugs Cable,Pvc Copper Cable,Cable With Copper Tube Terminal
Taixing Longyi Terminals Co.,Ltd. , https://www.lycopperlugs.com