【作者】 王珍；

【导师】 李友芬；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2016， 硕士

【摘要】 白光LED发光效率高、无污染、寿命长,是实现绿色照明的重要策略之一。采用荧光粉与LED芯片的有效结合可制备出理想的白光,荧光光粉性能的好坏对白光LED的显色效果产生直接影响。而太阳能电池可将无污染可再生的太阳能转化为电能运用在通讯／通电、石油、海洋等诸多领域,但由于太阳能电池光谱响应区域与太阳光谱不匹配,使其转光效率低下,因此,寻找合适的下转换发光材料将不能被太阳能电池吸收的紫外波段转换为可见-近红外波段具有重要意义。本论文采用固相反应法分别制备了近紫外激发的Y2SiO5:Ce3+蓝色荧光粉和Y2SiO5:Bi3+, Eu3+单一相全色荧光粉,以及适用于硅太阳能电池的下转换荧光粉Sr2SiO4:Ce3+,Tb3+,Yb3+。主要工作如下：1.采用固相法合成了单一相X2-Y2SiO5:Ce3+的发光材料。样品激发光谱是波长为280-370nm的带状谱,发射光谱主峰位于393及418nm左右,来自于Ce3+的4f→5d自旋允许跃迁。在添加B2O3、NaF、BaCO3作助熔剂中,Ba2+及Na+的掺杂能够显著提高样品的发光效果,当BaL2+及Na+的掺入量为1%时,样品发光强度分别提高1.8倍和1.4倍。2.采用固相法合成了主相结构为X2-Y2SiO5的Y2SiO5:Bi3+, Eu3+荧光粉。单掺Bi3+时,样品在近紫外激发下,分别在～358nm、～408nm、～490nm附近产生发射带,Bi3+的最佳掺杂浓度为1.5mol%。Bi3+, Eu3+共掺杂后导致样品在612nm出现Eu3+的典型发射主峰,对应Eu3+的5D0→7F2跃迁。通过调控Bi3+/Eu3+掺杂比,可实现样品从蓝光到红光的转变。3.对Sr2SiO4:Ce3+, Tb3+, Yb3+的发光性能进行了系统研究。Sr2SiO4:Yb3+在紫外激发下,由于Yb3+的2F5/2→2F7/2跃迁产生峰值位于977nm左右的近红外发射,与硅带隙宽匹配。通过Ce3+和Tb3+的引入,能够显著增强荧光粉在近红外的发射。机理分析表明,在三掺杂中,Ce3+与Tb3+之间通过电偶极对电偶极产生共振能量传递,Tb3+和Yb3+之间通过共合作能量传递过程,从而实现发光材料下转换。所得样品的最佳配比为：Sr2SiO4:4mol%Ce3+,6mol%Tb3+,3mol%Yb3+。更多还原

【Abstract】 The w-LED is considered as an environmental friendly lighting due to its advantages such as high lighting efficiency, pollution-free and long lifetime. The ideal of white light could be prepared by using the effective combination of phosphors and LED chips, therefore the fluorescent light powder performance is good or bad, which will influence directly on the color effect of white LED. Solar cells can be used in the communications/electricity, petroleum, marine, and many other areas as the pollution-free renewable solar energy because it can convert the solar energy into electrical energy. But the solar cell does not match with the solar spectrum, leading to the low efficiency for the light conversion. Therefore, looking for the right down-conversion luminescence materials is of great significance, in which the ultraviolet (UV) wavelengths unabsorbed by solar cells can be converted into the visible-near infrared (NIR) wave band.In this paper, Ce3+-doped and Bi3+-Eu3+ co-doped Y2SiO5 phosphors which have potential to be used for LED were synthesized by solid-state reaction method respectively. Ce3+-Tb3+-Yb3+tri-doped Sr2Si04 down-conversion material for Si solar cells were also studied.The thesis consists of the following results:1. The single phase X2-Y2Si05:Ce3+ phosphors were prepared by the solid-state method at high temperatures. The excitation spectra is a band spectrum of 280-370nm, and the emission peaks are located at 393nm and 418nm peaks, corresponding to 5d→4f spin allowed transition. With adding flux of B2O3, NaF and BaO, the luminescence intensity of specimens have been changed dramatically. The intensity can be enhanced to 1.8 times and 1.4 times respectively in the condition of 1wt%Ba2+ and 1wt%Na+.2. The Y2Si05:Bi3+, Eu3+ phosphors were prepared. Single Bi3+-doped Y2SiO5 exhibited three discernible emission peaks at-358,-408, and ～490 nm, respectively, upon UV excitation. When Eu3+ is codoped into Y2Si05:Bi3+, a red emission peaks at 612nm appeared, which is attribute to 5D0→7F2 of Eu3+ By adjusting the doping ratio of Bi3+/Eu3+, tunable emissions of phosphors between blue and red can be objected. Y2Si05:Bi3+, Eu3+ is a promising candidate of white light emitting.3. The luminescent properties of Sr2Si04:Ce3+, Tb3+, Yb3+ were studied. Single Yb3+-doped Y2Si05 exhibited a emission peak at 977 nm which is close to the band gap of Si solar cell. The near-infrared emission intensity was remarkably enhanced by adding Ce3+ and Tb3+ as sensitized ions. The Ce3+can transfer energy to Tb3+ ions by means of dipole-dipole interactions. Cooperative energy transfer occurred between Tb3+and Yb3+.The optimum doping concentration was obtained to be 4mol% Ce2+,6mol% Tb3+ and 3mol%Yb3+.更多还原