Investigations on the novel properties and packaging performance of phosphors in light-emitting diodes

• Main Authors: Yu-Sheng Tang, 湯友聖
• Other Authors: Shu-Fen Hu
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/499jj3

碩士 === 國立臺灣師範大學 === 光電科技研究所 === 96 === The development of blue light-emitting diodes (LEDs) is hindered mainly due to the difficulties in the processing. After the initial discovery of white light generation by using GaN based LEDs in combination with a yellow phosphor (cerium doped yttrium aluminum garnet, YAG:Ce) by Nakamura et al. of Nichia, a great progress has been achieved in the development of white LEDs. The light emitting diodes has several advantages over the conventional light sources such as energy saving, eco friendly characteristics and so on. Due to the arising eco-awareness, various nations target to achieve the goal of “Kyoto Protocol” of decreasing the levels of carbon dioxide in next 3～4 years. However, the above mentioned strategy of white light generation faces serious problems such as low conversion efficiency of blue LED and poor color rendering index. In this regard, silicate based phosphors have attracted much attention due to its superior luminescence properties in comparison with YAG. However the silicate based phosphors are also found to be thermally unstable. The present work is focused on near UV excitable phosphate based phosphors exhibiting high color saturation properties. We have observed that the luminescence of Eu2+ doped KSrPO4 is thermally more stable than YAG phosphor and not sensitive to moisture. The studies on Sr3(Al2O5)Cl2 doped with Eu2 were also performed which showed the peak broadening as well as red shift of the spectrum (PL) as compared to YAG. This provides the solution for problem of low color rendering index. The phosphor materials were characterized by various techniques such as X- ray diffraction analysis (XRD), scanning electron microscopy (SEM), photoluminescence (PL) measurements etc. A part of the present studies related to the KSrPO4 phosphor and its thermal stability has been published in the journal, Appl. Phys. Lett. 90, 151108 (2007) and we have also filed a patent on UV excitable Sr3(Al2O5)Cl2:Eu2+ phosphors for application in LEDs.