纳米发光材料电荷迁移激发光谱的红移机理研究

Theoretical investigation on red shift of charge transfer excitation spectrum for nano-sized phosphors

基于Kronig-Penney模型,得出了晶体材料禁带宽度或特定能级在禁带中的位置随着晶体体积畸变而变化的趋势,进而推断出Y_2O3:Eu^(3+)发光材料的零声子电荷迁移能E_(zp)将随着材料纳米尺寸的下降而下降.此外,Y_2O3:Eu^(3+)纳米发光材料晶格环境刚性的下降导致了发光中心电荷迁移(CT)态坐标偏差的增大,这意味着在CT激发中发光中心将跃迁至更高的振动能级。随着Y_2O3:Eu^(3+)发光材料纳米尺寸的下降,振动能E_(vib)的上升幅度小于零声子电荷迁移能E_(zp)的下降幅度,电荷迁移能蜀E_(CT)由此下降,CT激发光谱向低能端移动。

Based on Kronig-Penney model, the changing tendency of band gap or a particular level with the volume deformation in crystalline materials was derived. Based on the tendency, the zero-phonon chargetransfer （CT） energy Ezp was deduced to be decreased when the size of Y2O3：Eu^3＋ phosphor decreases in nano-scale. In addition, the rigidity decrease of lattice environment in Y2O3：Eu^3＋ nano-phosphor leads to the enlargement of CT state coordinate offset, an optical center would reach a higher vibration level Evib in CT excitation. The increasing magnitude in Evlb is smaller than the decreasing magnitude of Ezp when the size of Y2O3：Eu^3＋ phosphor decreases in nano-scale. As a result, the CT energy ECT is decreased, and the CT excitation spectrum shifts to lower energy.