OLED(Organic Light-Emitting Diode), also known as electromechanical laser display, organic light emitting semiconductor.Ching w. Tang, a chinese-american professor, found it in a laboratory in 1979.OLED display technology has the advantages of spontaneous light, wide Angle, almost infinite high contrast, low power consumption, high reaction speed and so on.
The basic structure of OLED
An indium tin oxide (ITO), a thin, transparent semiconductor, connected to the positive pole of electricity, plus another metal cathode, such as a sandwich.The whole structure includes：Hole transport layer(HTL)、Light-emitting layer(EL) And the electron transport layer(ETL).When the power supply to the appropriate voltage, the anode hole charge will be in the light emitting layer and cathode, produce light, according to its different formula to produce red, green and blue RGB trichromatic, constitute a basic color.The characteristics of OLED are their own luminescence. Unlike TFT and LCD need backlight, so the visibility and brightness are high.Secondly, low voltage demand and high power efficiency, combined with fast response, light weight, thin thickness, simple construction and low cost, are regarded as one of the most promising products of the 21st century.
- Display: active light, wide Angle of view;Fast response and stable image;High brightness, rich color, high resolution.
- Working conditions: drive low power, low energy consumption, can be compatible with solar cells, integrated circuits and so on.
- Wide adaptability: using glass substrate to realize large-area flat panel display;If you use flexible materials as a substrate, you can make a collapsible displayBecause OLED are all solid state, the vacuum device, shock resistance, resistance to low temperature (-40 ℃), and other characteristics, has very important application in military aspects, such as used as modern weapons such as tanks, aircraft display terminal.
OLED for spontaneous light material, don’t need to the back plate, wide Angle at the same time, uniform quality, quick response speed, color, use simple drive circuit can be more easily to glow, simple process and can be made into flexure type panel, conform to the principle of thin and short, application scope belong to small and medium size panel.
The luminescence principle of organic light-emitting diodes is similar to that of inorganic luminescent diodes.When components derived by direct current (dc) forward bias, combined with outside voltage energy will drive electrons and holes respectively by the cathode and anode injection element, when the two have met in the conduction, combined, which formed the so-called electronic – hole recombination.When the chemical molecules are excited by the foreign energy, if the electron spins and the ground state electron pair, then the single weight state, the light released by it is called fluorescence;On the contrary, if the excited state electron and the ground state electron spin are not pair and parallel, it is called triplet, the light released by it is called phosphorescence.
When the state of the electronic location by the excited state of high-energy order returned to the steady low order, its energy will respectively by a photon of light materials at room temperature and cannot be observed triplet phosphor, so the PM – OLED device the theoretical limit value of luminous efficiency is only 25%.