Study On Fluorescent Properties And Preparation Of LED With White Light

White light-emitting diode (LED) is a new kind of light source with many advantages such as energy conservation, environmental protection, low-power consumption and so on. Under the circumstances of global energy lack and global environmental protection, the usage of LED semiconductor lighting materials is a main approach to achieve the aim of environmental protection. At present, the main method to prepare white LED is using yellow fluorescent powder to spread on LED chips. The fluorescent powders of YAG doped with rare-earth metal have several good properties, such as good color with gentle temperature and thermal stability etc. yellow fluorescent powders of YAG in our country and even in the international world is a hot topic among researchers.Three main methods to prepare white LED were introduced in this paper, and several other color fluorescence powders’research progress was also mentioned. The classification of rare-earth luminescent materials, luminescent mechanism and luminescent properties were highlighted. There are several ways to prepare fluorescent powder of YAG, such as high temperature solid-phase method, spray pyrolysis method, combustion method, sol gel process and method of precipitation. In this paper, fluorescent powders of YAG is prepared under reducing atmosphere of N2—H2by high temperature solid method, the crystal structure and crystal phase of fluorescent powders under different calcining temperature were characterized by XRD and TEM, the result showed that the optimum temperature is1400℃and the optimum time is3hours. The influence on fluorescent powders with different Ce ions doped into was discussed, and these samples were characterized by XRD and fluorescent spectrometer. The result demonstrated that the as-synthesised fluorescent powder belong to the structure of Yttrium aluminum garnet structure of the cubic, and the optimum of Ce3+doped into the sample is0.06. When matrix of cationic such as Ga3+, Tb3+, Sm3+etc rare-earth metals were doped into to replaced Y3+, the emission peak shifted, improved the color of the fluorescent powder, better matched with blue LED.Gd2-x (MoO4)3:Eux3+red fluorescent powder was successfully prepared throng high temperature solid method. The products phase, powders’excitation spectrum and emission spectrum were characterized and studied by XRD and fluorescent spectrometer respectively. The result showed that the fluorescent powder belong to tetragonal scheelite structure, all the products can be excited by UV light at395nm and blue light at464nm to obtain the red characteristics of transition which belong to5D0â†'7F2of Eu3+, and the optimum burning temperature is950℃with sintering3hours. When the Li2CO3as solubilizer was added to the system, the quenching problem of Eu3+was solved, this enhance the concentration of Eu3+ doped into the system greatly, simultaneously the emission intensity of the fluorescence was improved also.