【摘要】：商用白光LED是由藍(lán)光In Ga N芯片和Ce:YAG熒光粉封裝在一起制成的,熒光粉混合于環(huán)氧樹(shù)脂/硅膠中并涂覆于芯片上。然而由于環(huán)氧樹(shù)脂/硅膠導(dǎo)熱性和化學(xué)穩(wěn)定性較差,在高功率芯片照射或者較高溫度使用環(huán)境下容易發(fā)生老化、黃化,造成LED色偏進(jìn)而嚴(yán)重縮短器件的使用壽命。另外,由于紅光成分的缺乏,此類(lèi)LED器件往往呈現(xiàn)出較高的色溫和較低的顯色指數(shù)。研究表明,與熒光粉相比,Ce:YAG熒光晶體呈現(xiàn)出更加優(yōu)異的光學(xué)性能和更高的熱穩(wěn)定性能。因此,本論文提出通過(guò)提拉法生長(zhǎng)出高質(zhì)量Ce:YAG單晶材料來(lái)替代傳統(tǒng)的商用熒光粉,并通過(guò)在Ce:YAG晶體中共摻雜稀土離子/過(guò)度金屬離子Tb,Mn,Eu等來(lái)增加發(fā)射光中的紅光成分,從而改善白光LED的相關(guān)光學(xué)性能。提拉法生長(zhǎng)得到高質(zhì)量的Ce:YAG,Ce,Tb:YAG,Ce,Mn:YAG,Ce,Mn,Tb:YAG及Ce,Eu:YAG 5種晶體。采用X射線(xiàn)粉末衍射技術(shù)(XRD),SEM/STEM,吸收(UV-vis)和熒光光譜(PL),變溫光譜,壽命衰減,X射線(xiàn)精細(xì)結(jié)構(gòu)譜(EXAFS),電子順磁共振譜(EPR),光電性能測(cè)試等手段對(duì)這五種晶體的光學(xué)性能進(jìn)行了詳細(xì)的分析研究。主要研究?jī)?nèi)容及結(jié)果如下:1、X射線(xiàn)粉末衍射(XRD)結(jié)果表明,稀土離子Tb,Eu和過(guò)渡金屬離子Mn的摻雜會(huì)導(dǎo)致YAG晶胞體積產(chǎn)生輕微的改變,但并不影響YAG晶體的晶相結(jié)構(gòu)。2、吸收光譜表明,Ce:YAG,Ce,Tb:YAG,Ce,Mn:YAG,Ce,Mn,Tb:YAG及Ce,Eu:YAG這5種晶體除了在發(fā)光中心460nm處均有著強(qiáng)烈的吸收(對(duì)應(yīng)于Ce~(3+)的4f→5d軌道的躍遷吸收)外,同時(shí)也出現(xiàn)了摻雜離子Tb,Mn,Eu的特征吸收峰,在460nm藍(lán)光激發(fā)下,5種晶體的發(fā)射光譜可由中心波長(zhǎng)約530nm(5d~(1 2)E_gГ8_g→4f~(1 2)F_(7/2)Г_(8u))的500nm~650nm寬帶發(fā)射峰組成,其中Ce,Mn:YAG和Ce,Mn,Tb:YAG晶體樣品的發(fā)射光譜中均出現(xiàn)了567nm的寬帶發(fā)射峰(Mn~(2+)的~4T_1→~6A_1的軌道躍遷),一定程度上彌補(bǔ)了紅光成分的缺失。3、研究了Ce,Mn,Tb:YAG晶體的在303K-563K溫度范圍內(nèi)的變溫光譜,結(jié)果表明,與商用熒光粉相比,隨著溫度的升高,單晶呈現(xiàn)出更小的光損失,具有更高的熱穩(wěn)定性。4、研究了Ce,Mn:YAG的X射線(xiàn)精細(xì)結(jié)構(gòu)譜(EXAFS)和電子順磁共振譜(EPR),結(jié)果表明摻雜的Mn離子的價(jià)態(tài)主要以+2價(jià)為主。5、測(cè)試了5種晶體與460 nm藍(lán)光芯片封裝而成的白光LED的光電參數(shù),探討了摻雜離子的種類(lèi)、晶片厚度、支架、AB膠、驅(qū)動(dòng)電流等對(duì)晶片發(fā)光性能的影響。結(jié)果表明,Tb離子的摻入能一定程度上降低白光LED的色溫,但顯色指數(shù)較低;Mn離子的摻入能夠提高白光LED的顯色指數(shù),降低色溫;Eu的摻入對(duì)Ce~(3+)的發(fā)光有淬滅作用。6、研究了Ce,Mn:YAG單晶片的H_2退火工藝,結(jié)果表明,合適溫度下的退火能夠消除晶體生長(zhǎng)和加工中產(chǎn)生的缺陷和應(yīng)力,一定程度上的提高了晶片的發(fā)光性能。
[Abstract]:Commercial white LED is made of blue In Ga N chip and Ce:YAG fluorescent powder. The phosphor is mixed in epoxy resin / silica gel and coated on the chip. However, due to the poor thermal conductivity and chemical stability of epoxy resin / silica gel, it is easy to aging and yellowing in the environment of high power chip irradiation or high temperature, resulting in LED color deviation and seriously shortening the service life of the device. In addition, due to the lack of red light composition, this kind of LED devices often show higher color temperature and lower color index. The results show that compared with the fluorescent powder, Ce:YAG fluorescence crystal has better optical properties and higher thermal stability. Therefore, in this paper, high quality Ce:YAG single crystal materials are grown by Czochralski method to replace the traditional commercial phosphors, and rare earth ions / excessive metal ions Tb,Mn, are co-doped in Ce:YAG crystals. Eu et al., etc., to increase the red light composition in the emitted light, so as to improve the related optical properties of white light LED. High quality Ce:YAG,Ce,Tb:YAG,Ce,Mn:YAG,Ce,Mn,Tb:YAG and Ce,Eu:YAG crystals were obtained by Czochralski method. X-ray powder diffraction technique (XRD), SEM/STEM, absorption (UV-vis) and fluorescence spectrum (PL), variable temperature spectrum, lifetime decay, X-ray fine structure spectrum (EXAFS), electron parammagnetic resonance spectrum (EPR), The optical properties of these five crystals were analyzed and studied in detail by means of photoelectric performance test. The main research contents and results are as follows: 1. X-ray powder diffraction (XRD) results show that the doping of rare earth ion Tb,Eu and transition metal ion Mn can lead to a slight change in the cell volume of YAG. However, the crystal phase structure of YAG crystal is not affected. 2, the absorption spectra show that Ce:YAG,Ce,Tb:YAG,Ce,Mn:YAG,Ce,Mn,Tb:YAG and Ce, The five crystals of Eu:YAG not only have strong absorption at the luminous center 460nm (corresponding to the transition absorption of 4f 鈮，

本文編號(hào)：2483899