發光二極體用之多光色螢光材料合成與特性分析

Abstract

本研究著重於螢光粉與量子點之合成與分析，螢光粉包含適用藍光與紫外光激發，量子點以銦磷(InP)之奈米結構。藍光激發螢光粉為鋰鍶矽酸鹽類(Li2SrSiO4:Ce3+,Eu2+)、釔鋁氧化物(Y3Al5O12:Ce3+)與氮化物(CaAlSiN3:Eu2+)，由同步輻射吸收光譜，獲知發光中心之價數變化情況；以半衰期與理論計算證實發光中心間之作用力，探討缺陷形成能量；成功實際封裝高演色性(Ra = 93)之白光，利用黃色螢光粉添加紅色氮化物以提高白光演色性。 紫外光激發螢光粉主要為成長鋰鍶磷酸鹽(LiSrPO4)單晶，成功地解出新穎之單晶結構，並操作第一原理計算鉀鍶磷酸鹽(KSrPO4)摻雜銪(Eu)之主體能隙與發光中心之電子傳遞機制；以同步輻射真空紫外光波長172 nm激發矽酸鹽類(BaY2Si3O10)，可應用於電漿顯示器之新穎化合物；此外，利用共摻雜發光中心之硼酸鹽類(ZnB2O4:Bi3+, Eu3+)以提高紅光發光效率；且單一化合物(NaSrBO3:Ce3+, Tb3+, Sm3+)摻雜三種發光中心即可形成白光，可大幅地降低成本。 銦磷量子點，乃利用水熱法合成顆粒大小不同之奈米結構，因能隙不同以調控其發光光色；藉由細胞毒性測試得知其毒性極低；其可適用於藍光與紫外光激發，成功地封裝紅光發光二極體。

Examining the photoluminescence spectra, it was confirmed that the energy transfer from Ce3+ ions to Eu2+ rarely contribute to the luminescent enhancement of Li2SrSiO4:Ce3+,Eu2+. The proposed argument was validated with the first principle calculation about the defects formation energies. Furthermore, a mixture of Y3Al5O12:Ce3+ and CaAlSiN3:Eu2+ was coated on a blue light-emitting diodes (LEDs), the resultant white LEDs had a high luminous efficacy of ηL = 68 lm/W, a high color rendering index of Ra = 93, and a color temperature of CCT = 3,007 K (at 50 mA). On the other hand, we also emphasized that the physical and chemical properties of UV-LED pumped phosphors such as phosphate ABPO4:RE (A = Li, K; B = Sr, Ba; RE = Eu2+, Tb3+ and Sm3+), BaY2Si3O10:RE (RE = Ce3+, Tb3+, Eu3+), ZnB2O4:Bi3+, Eu3+ and NaSrBO3:RE (RE = Ce3+, Tb3+, Sm3+). This study elucidated the crystalline structure and lattice parameters of the products via a solid state reaction, using powder X-ray diffraction (XRD) and general structure analysis system (GSAS) refinement. The density functional calculations are performed using the generalized gradient approximation plus an on-site Coulomb interaction correction (GGA+U) scheme to investigate the electronic structures of the KSrPO4 system. Therefore, we proposed a novel mixture of variously colored quantum dots (InP) and silicone resin as a color-converting material, which can be applied to a UV-LED or Blue-LED chip. In the case of non-toxic InP QDs, the full color emission wavelengths can be easily adjusted by controlling the particle size (quantum confinement effect), and such QDs can be dispersed uniformly in silicone resin. This fact can perhaps be exploited to solve the problems of the efficiency and coating technology of LED devices.