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How Does Oled Display Work

May 18, 2018

The basic structure of an OLED display is composed of a thin and transparent indium tin oxide (ITO) with a semi-conductor characteristic, which is connected to the positive electrode of electricity, and another metal cathode, which is formed into a sandwich structure. The entire structural layer includes a hole transport layer (HTL), a light emitting layer (EL) and an electron transport layer (ETL). When the power is supplied to an appropriate voltage, positive hole and cathode charges are combined in the light emitting layer to produce light, and red, green, and blue RGB primary colors are generated according to different recipes to form a basic color. The characteristics of OLEDs are self-illumination, unlike TFT LCDs that require backlights, so visibility and brightness are high, followed by low voltage requirements and high power-saving efficiency, coupled with fast response, light weight, thin thickness, simple construction, and low cost Etc., is considered one of the most promising products of the 21st century. The

The light emitting principle of organic light emitting diodes is similar to that of inorganic light emitting diodes. When the element is subjected to direct bias derived from direct current (DC), the applied voltage energy will drive electrons and holes to inject elements from the cathode and the anode, respectively, when the two meet in conduction. In combination, a so-called Electron-Hole Capture is formed. When a chemical molecule is excited by external energy, if the electron spin is paired with the ground state electron, it is a singlet, and the released light is so-called Fluorescence; The state electrons and the ground electron spins are not parallel and parallel, and they are called triplets. The light they release is the so-called Phosphorescence. The

When the electron's state position returns from the excimer high energy level to the steady state low energy level, its energy will be emitted in the form of Light Emission or Heat Dissipation, respectively. The photon part can be used as a display function. However, the triplet phosphorescence cannot be observed at room temperature in the organic fluorescent material, so the theoretical limit of the luminous efficiency of the PM-OLED device is only 25%. The

The principle of PM-OLED light emission is to use the energy level difference of the material to convert the released energy into photons, so we can choose the appropriate material as the light emitting layer or dope the dye in the light emitting layer to get the light color we need. In addition, the combined reaction of electrons and holes is generally within tens of nanoseconds (ns), so the response speed of PM-OLEDs is very fast. The

P.S.: Typical structure of PM-OLED. A typical PM-OLED is composed of a glass substrate, an indium tin oxide (ATO) anode, an organic light emitting layer (Emitting Material Layer), a cathode (Cathode), and the like, wherein the thin and transparent ITO anode The organic light-emitting layer is sandwiched with a metal cathode like a sandwich. When holes (holes) injected into the anode and electrons of the cathode (electron) are combined in the organic light-emitting layer, the organic material is excited to emit light. The

At present, the multi-layer PM-OLED structure with better luminous efficiency and commonly used, in addition to the glass substrate, the yin and yang electrodes and the organic light-emitting layer, a hole injection layer (HIL) and a hole transport layer are still required to be fabricated. Hole Transport Layer (HTL), Electron Transport Layer (ETL), Electron Inject Layer (EIL), etc., and an insulating layer is required between each transport layer and the electrode, so the thermal evaporation (Evaporate) ) The difficulty of processing is relatively high 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 must be protected by encapsulation. 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 to 1,500 Å (0.10 to 0.15 um), and the total thickness of the entire display panel (Panel) is less than 200 μm after the package is filled with desiccant. (2mm), with the advantage of thinness