【作者】 赵玉晶；

【导师】 何大伟；

【作者基本信息】 北京交通大学 ， 光学， 2010， 硕士

【摘要】 白光LED是一种新型的固体照明光源。目前制备白光LED的主流方法是采用荧光粉转换方法。而以硅酸盐为单一基质的白光荧光粉由于其良好的发光性能,成为白光LED照明的研究热点。本文采用溶胶凝胶法合成了Sr2SiO4：Dy3+以及Dy3+,Eu3+系列共激活的Sr2SiO4高亮度白光LED用荧光粉,并对其结构特性及近紫外光激发下的发光特性进行了研究。利用XRD、SEM等手段对样品Sr2SiO4：Dy3+,Eu3+进行表征,并测试其发光性能。对Sr2SiO4：Dy3+荧光粉的光谱分析表明,样品有几个明显的激发峰,分别位于325nm、350nm、365nm和386nm附近,分别对应Dy3+离子6H15／2→6P3／2,6H15／2→6P7／2,6H15／2→6P5／2,6H15／2→4M21／2的跃迁。在386nm近紫外光激发下样品的发射主峰位于486nm、491nm、577nm附近,其中486nm和491nm的发射峰对应于Dy3+离子4F9／2→6H15／2的跃迁,577nm对应于Dy3+离子4F9／2→6H13／2的发射跃迁,蓝光与黄光复合产生白光发射。研究了Dy3+掺杂浓度对Sr2SiO4：Dy3+材料发射光谱强度的影响。进一步分析计算其色坐标为(0.35,0.38),与白光的最佳色坐标(0.33,0.33)相差很多,需要进一步改善红光发射部分。为了增强红光发射,我们制备了Dy3+,Eu3+共掺杂的Sr2SiO4样品,光谱分析表明,除了Dy3+在蓝色发射带和黄色发射带的特征发光峰之外,在610-620nm处有一宽谱带发射峰,为Eu3+的5D0—7F2能级的跃迁发射,红光区的发射有所增强。通过不断改变掺杂Eu3+离子含量,并分析其光谱的变化特性,得到最接近白光的稀土掺杂浓度,即Dy3+的掺杂浓度为4mol%,Eu3+的掺杂浓度约为1mol%,色温为5603K。另外,还研究了退火温度及电荷补偿剂对于样品发光强度的影响。当温度由900℃逐渐升高到1100℃时,样品的发光强度明显增强。进一步提高退火温度时,发现发光强度几乎不发生变化。随着电荷补偿剂浓度的增大,Sr2SiO4：Dy3+,Eu3+材料发射光谱强度先增大、后减小。当掺入的电荷补偿剂不同时,增强的效果亦不同,其中以加入Li+情况最为明显。更多还原

【Abstract】 White LED is a new-style solid state light source. Presently, it is the main way to make white LED combining with phosphors. And the single matrix white light silicate phosphor has attracted much research interest in the area of illumination due to its superiorities in luminescence properties.Sr2SiO4:Dy3+and Sr2SiO4:Dy3+, Eu3+phosphors for white LED were prepared via sol-gel process. The structure and emission spectra excited by near violet light were investigated.The structure of all the samples were characterized by Powder X-ray diffraction(XRD), the morphologies of the samples were observed by scanning electron microscopy(SEM) and the excitation and emission spectra of samples were obtained using fluorescence spectrophotometer.The excitation spectra of Sr2SiO4:Dy3+show strong absorption near 325nm、350nm、365nm and 386nm due to H15/2→6P3/2,6H15/2→6P7/2,6H15/2→6P5/2,6H15/2→4M21/2 transition of Dy+. The emission spectrum of Dy3+has three groups of emissions located at about 479nm、491nm、571nm under 386nm UV excitation. The emission peaks at 479nm and 491nm (Blue) attribute to the 4F9/2→6H15/2 transition and 571nm (Yellow) attributes to the 4F9/2→6H13/2 transition. The two colors make white light. The effect of Dy3+concentration on the emission spectrum intensity of Sr2SiO4:Dy3+was investigated. The color coordinates (CIE) analysis indicates Sr2SiO4:Dy3+is located at (0.35,0.38) which is near white color region, but not at the best location. Therefore, it is necessary to improve the red light emission.The emission spectrum of Eu3+and Dy3+co-doped Sr2SiO4 phosphors under UV excitation were investigated for enhancing red emission. The emission spectrum consists of three bands. The blue and yellow bands attribute to Dy3+ions and the red band from 610nm to 620nm attributes to the 5D0—7F2 transition of Eu3+ions. The emission intensity of red band is lightly enhanced.The effect of Eu3+concentration on the emission spectrum intensity of Sr2SiO4: Dy3+, Eu3+was investigated. The best doping concentration for white phosphors was achieved when the concentration for Eu3+and Dy3+were 1mol% and 4mol%, respectively. And the corresponding color temperature of the Sr2SiO4:0.04Dy3+, 0.01Eu3+was 5603K. In addition, several experimental factors such as annealing temperature and the condition of the charge compensation, which had influence on the photoluminescence (PL) intensity of Sr2SiO4: Dy3+, Eu3+phosphors were also studied. As the annealing temperature increased from 900℃to 1100℃, the PL intensity was significantly enhanced. However, the PL intensity showed almost no change when the annealing temperature was further increased. The effect of charge compensation on the emission spectra of Sr2SiO4:Dy3+, Eu3+phosphor was also studied. The emission spectra intensity of Sr2SiO4: Dy3+, Eu3+phosphor firstly increased to a maximum value and then began to decrease with the continuously increasing of the charge compensation concentration. Furthermore, different charge compensations showed different effect on the emission intensity, and the most obvious effect was observed when Li+is employed as the charge compensation.There are 23 figures,4tables and 44 references in this paper.更多还原