無機矽酸鹽與磷酸鹽螢光體能量傳遞之研究

Abstract

本研究利用固態合成法製備Ce3+/Tb3+共摻Ca8La2(PO4)6O2及Sr4Y6(SiO4)6O、Eu2+/Mn2+共摻CaScAlSiO6與Ce3+單摻之Sr8La2(PO4)6O2等磷酸鹽及矽酸鹽螢光體，以XRD和螢光光譜儀進行其結構與發光特性的鑑定，並探討其能量傳遞機制及臨界距離，此外亦量測其螢光衰變、CIE色度座標、量子效率，並進一步將所製備之螢光體應用於白光LED的封裝。 本論文研究中第一部分為Ce3+/Tb3+共摻Ca8La2(PO4)6O2及Sr4Y6(SiO4)6O螢光體能量傳遞之探討，其中Ce3+為敏化劑而Tb3+為活化劑，本研究發現在Ca8La2(PO4)6O2：Ce3+, Tb3+及Sr4Y6(SiO4)6O：Ce3+, Tb3+主體中能量傳遞皆為偶極-偶極交互作用。 第二部分則探討了Eu2+/Mn2+共摻CaScAlSiO6螢光體中之能量傳遞，以Mn2+作為活化劑時，在可見光區的放光為dd的能階躍遷，在光學選擇律中屬於宇稱及自旋禁制，所以在紫外或可見光的激發下，其發光訊號很微弱，當Eu2+/Mn2+共摻時，以Eu2+作為敏化劑而Mn2+作為活化劑，經由能量傳遞提升Mn2+放光強度，其能量傳遞機制為偶極-四極交互作用，透過不同Eu2+/Mn2+濃度比例調配其色調，搭配紫外LED晶片封裝為白光二極體。 最後一部分為探討Ce3+單摻之Sr8La2(PO4)6O2螢光體之發光特性，最佳激發波長為356 nm，放射520 nm的黃綠色光，其可搭配商用螢光粉及紫外LED晶片應用於白光發光二極體之封裝。

In this study, Ca8La2(PO4)6O2:Ce3+,Tb3+, Sr4Y6(SiO4)6O:Ce3+,Tb3+, CaScAlSiO6:Eu2+,Mn2+ and Sr8La2(PO4)6O2:Ce3+ were synthesized by solid state method. The structure, luminescence and chromaticity properties, and quantum efficiency of phosphors were characterized by X-ray powder diffraction, fluorescence spectroscopy. We investigated the mechanism of energy transfer and critical distance in these silicate and phosphate phosphors. Finally, these phosphors we synthesized are applied to the fabrication of white-light LEDs. The first part investigates the energy transfer mechanism between Ce3+ and Tb3+in Ca8La2(PO4)6O2 and Sr4Y6(SiO4)6O.The Ce3+ acts as a sensitizer and Tb3+ acts as an activator. In Ce3+/Tb3+ codoped phosphors, the intensity of luminescence in long wavelength range was increased through the energy transfer. Based on the analysis, the energy transfer mechanism from Ce3+ to Tb3+ was via dipole-dipole interaction. The second part investigates the Eu2+Mn2+ energy transfer in the CaScAlSiO6:Eu2+,Mn2+, where Mn2+ acts as a activator, and Eu2+ serves as a sensitizer to enhance the luminescence of Mn2+ through the energy transfer. Based on the analysis, the energy transfer mechanism from Eu2+ to Mn2+ was via dipole-quadrupole interaction. By adjusting the ratio between Eu2+ and Mn2+, we can make adjust the hue and the phosphor can also be used for fabrication of single-composition white-light LED. The final part describes the luminescence characterization, quantum efficiency and fluorescence decay of Sr8La2(PO4)6O2:Ce3+. Its excitation band is in the range of n-UV, and the emission wavelength is 520 nm. It is suitable for the White-LED fabrication by combining commercial phosphors and UV-LED chip.