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1、<p><b> 發(fā)光二極管</b></p><p> LED(Light Emitting Diode),發(fā)光二極管,是一種固態(tài)的半導體器件,它可以直接把電轉(zhuǎn)化為光。LED的心臟是一個半導體的晶片,晶片的一端附在一個支架上,一端是負極,另一端連接電源的正極,使整個晶片被環(huán)氧樹脂封裝起來。半導體晶片由兩部分組成,一部分是P型半導體,在它里面空穴占主導地位,另一端是N型半導體,在
2、這邊主要是電子。但這兩種半導體連接起來的時候,它們之間就形成一個“P-N結(jié)”。當電流通過導線作用于這個晶片的時候,電子就會被推向P區(qū),在P區(qū)里電子跟空穴復(fù)合,然后就會以光子的形式發(fā)出能量,這就是LED發(fā)光的原理。而光的波長也就是光的顏色,是由形成P-N結(jié)的材料決定的。 </p><p> 50年前人們已經(jīng)了解半導體材料可產(chǎn)生光線的基本知識,第一個商用二極管產(chǎn)生于1960年。LED是英文light emittin
3、g diode(發(fā)光二極管)的縮寫,它的基本結(jié)構(gòu)是一塊電致發(fā)光的半導體材料,置于一個有引線的架子上,然后四周用環(huán)氧樹脂密封,即固體封裝,所以能起到保護內(nèi)部芯線的作用,所以LED的抗震性能好。</p><p> 發(fā)光二極管的核心部分是由P型半導體和N型半導體組成的晶片,在P型半導體和N型半導體之間有一個過渡層,稱為P-N結(jié)。在某些半導體材料的PN結(jié)中,注入的少數(shù)載流子與多數(shù)載流子復(fù)合時會把多余的能量以光的形式釋放
4、出來,從而把電能直接轉(zhuǎn)換為光能。PN結(jié)施加反向電壓時,少數(shù)載流子難以注入,故不發(fā)光。這種利用注入式電致發(fā)光原理制作的二極管叫發(fā)光二極管,通稱LED。 當它處于正向工作狀態(tài)時(即兩端加上正向電壓),電流從LED陽極流向陰極時,半導體晶體就發(fā)出從紫外到紅外不同顏色的光線,光的強弱與電流有關(guān)。 </p><p> 最初LED用作儀器儀表的指示光源,后來各種光色的LED在交通信號燈和大面積顯示屏中得到了廣泛應(yīng)用,產(chǎn)生了
5、很好的經(jīng)濟效益和社會效益。以12英寸的紅色交通信號燈為例,在美國本來是采用長壽命、低光效的140瓦白熾燈作為光源,它產(chǎn)生2000流明的白光。經(jīng)紅色濾光片后,光損失90%,只剩下200流明的紅光。而在新設(shè)計的燈中,Lumileds公司采用了18個紅色LED光源,包括電路損失在內(nèi),共耗電14瓦,即可產(chǎn)生同樣的光效。 汽車信號燈也是LED光源應(yīng)用的重要領(lǐng)域。 </p><p> 對于一般照明而言,人們更需要白色的光源
6、。1998年白光的LED開發(fā)成功。這種LED是將GaN芯片和釔鋁石榴石(YAG)封裝在一起做成。GaN芯片發(fā)藍光(λp=465nm,Wd=30nm),高溫燒結(jié)制成的含Ce3+的YAG熒光粉受此藍光激發(fā)后發(fā)出黃色光射,峰值550nm。藍光LED基片安裝在碗形反射腔中,覆蓋以混有YAG的樹脂薄層,約200-500nm。 LED基片發(fā)出的藍光部分被熒光粉吸收,另一部分藍光與熒光粉發(fā)出的黃光混合,可以得到得白光。現(xiàn)在,對于InGaN/YAG白色
7、LED,通過改變YAG熒光粉的化學組成和調(diào)節(jié)熒光粉層的厚度,可以獲得色溫3500-10000K的各色白光。這種通過藍光LED得到白光的方法,構(gòu)造簡單、成本低廉、技術(shù)成熟度高,因此運用最多。 </p><p> 上個世紀60年代,科技工作者利用半導體PN結(jié)發(fā)光的原理,研制成了LED發(fā)光二極管。當時研制的LED,所用的材料是GaASP,其發(fā)光顏色為紅色。經(jīng)過近30年的發(fā)展,現(xiàn)在大家十分熟悉的LED,已能發(fā)出紅、橙、
8、黃、綠、藍等多種色光。正是這些彩色光源使LED廣泛用來顯示文字、圖形、圖像、動畫、行情、視頻、錄像信號等各種信息。</p><p> LED顯示屏分為圖文顯示屏和視頻顯示屏,均由LED矩陣塊組成。圖文顯示屏可與計算機同步顯示漢字、英文文本和圖形;視頻顯示屏采用微型計算機進行控制,圖文、圖像并茂,以實時、同步、清晰的信息傳播方式播放各種信息,還可顯示二維、三維動畫、錄像、電視、VCD節(jié)目以及現(xiàn)場實況。LED顯示屏
9、顯示畫面色彩鮮艷,立體感強,靜如油畫,動如電影,廣泛應(yīng)用于金融、稅務(wù)、工商、郵電、體育、廣告、廠礦企業(yè)、交通運輸、教育系統(tǒng)、車站、碼頭、機場、商場、醫(yī)院、賓館、銀行、證券市場、建筑市場、拍賣行、工業(yè)企業(yè)管理和其它公共場所。 </p><p> LED顯示屏可以顯示變化的數(shù)字、文字、圖形圖像;不僅可以用于室內(nèi)環(huán)境還可以用于室外環(huán)境,具有投影儀、電視墻、液晶顯示屏無法比擬的優(yōu)點。</p><p&
10、gt; LED之所以受到廣泛重視而得到迅速發(fā)展,是與它本身所具有的優(yōu)點分不開的。這些優(yōu)點概括起來是:亮度高、工作電壓低、功耗小、小型化、壽命長、耐沖擊和性能穩(wěn)定。LED的發(fā)展前景極為廣闊,目前正朝著更高亮度、更高耐氣候性、更高的發(fā)光密度、更高的發(fā)光均勻性,可靠性、全色化方向發(fā)展。</p><p> Light Emitting Diode</p><p> LED (Light Em
11、itting Diode), light-emitting diode, is a solid state semiconductor devices, which can be directly converted into electricity to light. LED is the heart of a semiconductor chip, the chip is attached to one end of a stent
12、, is the negative side, the other end of the power of the cathode, the entire chip package to be epoxy resin. Semiconductor chip is composed of two parts, part of the P-type semiconductor, it inside the hole-dominated, t
13、he other side is the N-type semiconductor, here</p><p> 50 years ago, people have to understand semiconductor materials can produce light of the basic knowledge, the first commercial diodes in 1960. English
14、 is the LED light emitting diode (LED) acronym, and its basic structure is an electroluminescent semiconductor materials, placed in a wire rack, then sealed with epoxy resin around, that is, solid package, Therefore, the
15、 protection of the internal batteries can play the role of line, so the seismic performance LED good. </p><p> LED is the core of the P-type semiconductor and components of the N-type semiconductor chips, t
16、he P-type semiconductor and N-type semiconductor between a transition layer, called the PN junction. In some semiconductor materials in the PN junction, the injection of a small number of carrier-carrier and the majority
17、 of the extra time will be in the form of light energy to release, thus the power to direct conversion of solar energy. PN junction on reverse voltage, a few hard-carrier injection, it </p><p> Instruments
18、used for the first LED light source instructions, but all kinds of light colored LED lights in traffic and large screen has been widely applied, have a very good economic and social benefits. The 12-inch red traffic ligh
19、ts as an example, is used in the United States have long life, low-efficiency 140 watt incandescent lamp as a light source, it produced 2,000 lumens of white light. The red filter, the loss-90 percent, only 200 lumens of
20、 red light. In the light of the new design, Lumi</p><p> For general lighting, people need more white light sources. The 1998 white LED successful development. This is the GaN LED chip and Yttrium Aluminum
21、Garnet (YAG) package together cause. GaN chip of the Blu-ray (λ p = 465nm, Wd = 30nm), made of high-temperature sintering of the Ce3 + YAG phosphors excited by this Blu-ray after irradiating a yellow, the peak 550 nm. Bl
22、ue-chip installed in the LED-based Wanxing reflection in the cavity, covered with a resin mixed with YAG thin layer, about 200-500 </p><p> In the 1960s, the use of science and technology workers semiconduc
23、tor PN junction of The principle of developing a LED light-emitting diodes. At that time, the development of LED, the materials used are GaASP, its luminous color is red. After nearly 30 years of development, and now we
24、are very familiar with the LED, has been sent to red, orange, yellow, green, blue, and other shade. Used to display text, graphics, animation, market, image and video, video signal etc all kinds of information of t</p
25、><p> The LED display screen and video display into the text by LED matrix blocks. Graphic display can be displayed with computer, English, Chinese text and graphics, Video screen using microcomputer control,
26、graphic, image, with real-time, synchronization, clear information dissemination way play all kinds of information, but also shows 2d, 3d animation, videos, TV, VCD programs and live. The LED display screen display brigh
27、t colors, stereo sense is strong, such as oil, such as films, widely used in </p><p> The LED display can display the change of digital image; text, graphics, Not only can be used for indoor environment can
28、 also be used in outdoor environment, projectors, LCD TV wall, and the incomparable advantages. </p><p> LED by the wide attention and rapid development, and it is the advantages of itself. These advantages
29、 in is: high brightness, working voltage, low consumption, miniaturization, impact resistance and long service life and stable performance. LED the development prospect, is currently towards a higher brightness, higher r
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