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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(dǎo)體器件,它可以直接把電轉(zhuǎn)化為光。LED的心臟是一個(gè)半導(dǎo)體的晶片,晶片的一端附在一個(gè)支架上,一端是負(fù)極,另一端連接電源的正極,使整個(gè)晶片被環(huán)氧樹(shù)脂封裝起來(lái)。半導(dǎo)體晶片由兩部分組成,一部分是P型半導(dǎo)體,在它里面空穴占主導(dǎo)地位,另一端是N型半導(dǎo)體,在
2、這邊主要是電子。但這兩種半導(dǎo)體連接起來(lái)的時(shí)候,它們之間就形成一個(gè)“P-N結(jié)”。當(dāng)電流通過(guò)導(dǎo)線作用于這個(gè)晶片的時(shí)候,電子就會(huì)被推向P區(qū),在P區(qū)里電子跟空穴復(fù)合,然后就會(huì)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(zhǎng)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(dǎo)體材料可產(chǎn)生光線的基本知識(shí),第一個(gè)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(xiě),它的基本結(jié)構(gòu)是一塊電致發(fā)光的半導(dǎo)體材料,置于一個(gè)有引線的架子上,然后四周用環(huán)氧樹(shù)脂密封,即固體封裝,所以能起到保護(hù)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(dǎo)體和N型半導(dǎo)體組成的晶片,在P型半導(dǎo)體和N型半導(dǎo)體之間有一個(gè)過(guò)渡層,稱為P-N結(jié)。在某些半導(dǎo)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(shí)會(huì)把多余的能量以光的形式釋放
4、出來(lái),從而把電能直接轉(zhuǎn)換為光能。PN結(jié)施加反向電壓時(shí),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(dāng)它處于正向工作狀態(tài)時(shí)(即兩端加上正向電壓),電流從LED陽(yáng)極流向陰極時(shí),半導(dǎo)體晶體就發(fā)出從紫外到紅外不同顏色的光線,光的強(qiáng)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(lái)各種光色的LED在交通信號(hào)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(jì)效益和社會(huì)效益。以12英寸的紅色交通信號(hào)燈為例,在美國(guó)本來(lái)是采用長(zhǎng)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(jì)的燈中,Lumileds公司采用了18個(gè)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(hào)燈也是LED光源應(yīng)用的重要領(lǐng)域。 </p><p> 對(duì)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(kāi)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(lán)光(λp=465nm,Wd=30nm),高溫?zé)Y(jié)制成的含Ce3+的YAG熒光粉受此藍(lán)光激發(fā)后發(fā)出黃色光射,峰值550nm。藍(lán)光LED基片安裝在碗形反射腔中,覆蓋以混有YAG的樹(shù)脂薄層,約200-500nm。 LED基片發(fā)出的藍(lán)光部分被熒光粉吸收,另一部分藍(lán)光與熒光粉發(fā)出的黃光混合,可以得到得白光?,F(xiàn)在,對(duì)于InGaN/YAG白色
7、LED,通過(guò)改變YAG熒光粉的化學(xué)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(guò)藍(lán)光LED得到白光的方法,構(gòu)造簡(jiǎn)單、成本低廉、技術(shù)成熟度高,因此運(yùn)用最多。 </p><p> 上個(gè)世紀(jì)60年代,科技工作者利用半導(dǎo)體PN結(jié)發(fā)光的原理,研制成了LED發(fā)光二極管。當(dāng)時(shí)研制的LED,所用的材料是GaASP,其發(fā)光顏色為紅色。經(jīng)過(guò)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(lán)等多種色光。正是這些彩色光源使LED廣泛用來(lái)顯示文字、圖形、圖像、動(dòng)畫(huà)、行情、視頻、錄像信號(hào)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(jì)算機(jī)同步顯示漢字、英文文本和圖形;視頻顯示屏采用微型計(jì)算機(jī)進(jìn)行控制,圖文、圖像并茂,以實(shí)時(shí)、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(dòng)畫(huà)、錄像、電視、VCD節(jié)目以及現(xiàn)場(chǎng)實(shí)況。LED顯示屏
9、顯示畫(huà)面色彩鮮艷,立體感強(qiáng),靜如油畫(huà),動(dòng)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(yùn)輸、教育系統(tǒng)、車站、碼頭、機(jī)場(chǎng)、商場(chǎng)、醫(yī)院、賓館、銀行、證券市場(chǎng)、建筑市場(chǎng)、拍賣行、工業(yè)企業(yè)管理和其它公共場(chǎng)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(wú)法比擬的優(yōu)點(diǎn)。</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(diǎn)分不開(kāi)的。這些優(yōu)點(diǎn)概括起來(lái)是:亮度高、工作電壓低、功耗小、小型化、壽命長(zhǎng)、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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