Leds đầy màu sắc

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Diode phát ra ánh sáng LED, được phát minh vào năm 1962 trên các thí nghiệm Electroluminescence Được gọi là "diode" bởi vì các bộ phận phát ra ánh sáng được cấu tạo bởi giàu điện tử bán dẫn kết nối với một trong nhiều lỗ khác, lỗ có thể được xem như là các hạt tích điện dương

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Nội dung Text: Leds đầy màu sắc

Contents 1. General knowledge about LED 2. The structure 3. Operation principle 4. Colors of LED
What is LED? LED- Light emitting diode, was invented in 1962 on electroluminescence experiments Called as “diode” because of the light emitting parts are composed by electron-rich semiconductor connected to the other hole-rich one, the hole can be viewed as positively charged particles
What is LED? Nowadays, LEDs are semiconductor light source used as indicator lamps in many devices and are increasingly used for other lighting with the variability across the visible, ultraviolet and infrared wavelengths, and very high brightness
Kinds of LED Low/Medium power LEDs: High power LEDs: used to the current used isn‟t higher illuminate surfaces and than 150mA, mostly used to wholeenvironments. obtain light signals or Single chip Power LEDs decoration and Multi chip Power LEDs
Structure
Structure: materials The semiconductor gallium arsenide (GaAs) was used in early LEDs. Later, GaP was used as the light-emitter to achieve pale green light. Blue LEDs using silicon carbide (SiC) and ultrabright blue LEDs made of gallium nitride (GaN) Super-bright red. yellow, and green LEDs were produced by using gallium aluminum arsenide phosphide (GaAIAsP). Materials with refractive index that could allow light to „get out‟
Operation: electroluminescence LEDs give off lights on the principle of electrical luminescence known as electroluminescence
Operation When LED is in term of forward- bias Charge-carriers electrons and holes flow into the junction from electrodes with different voltages
Operation When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon
Operation: band gap The band gap of the semicondutor substrate is just right equal to the energy of an emitted photon, that determine the wavelength and color of lights
Colors LEDs are available in red, orange, amber, yellow, green, blue and white. Blue and white LEDs are much more expensive than the other colours
Colors The color of LED is determined by the semiconductor material, not by the colors of the 'package' ( the plastic body)
Colors: monochromatic Human eye can see light with wavelengths from 380 nm (violet light) to 720 nm (red light). And the wavelength of the light emitted, and thus its color depends on the band gap energy of the materials forming the p-n junction
Colors: monochromatic So if we want a red- light emitting LED we will design a band gap materials in the range of 1.7 eV The compound semiconductors of the gallium (Ga) as GaAs, GaAsP AlGaP GAP , , , InGaN have slot values range from 1 eV to 3.5 eV and it can emit all colors of visible light
Colors: monochromatic
Colors: white LEDs There are 2 primary ways of producing high intensity white- light using LEDs
Colors: white LEDs One is to use individual LEDs that emit three primary colors red, green, and blue and then mix all the colors to form white light
Colors: white LEDs That method is called multi- colored white LEDs (sometimes referred to as Red Green Blue LEDs). RGB LEDs need electronic circuits to control the blending and diffussion of different colors