通过在YAG:Ce^(3+)和YAG:Ce^(3+),Pr^(3+)荧光粉体系中分别掺入Cr^(3+)离子来提高蓝光管芯白光LED的显色指数。Cr^(3+)离子的加入,增加了红光发射,这归因于Cr^(3+)的^2E-^4A2跃迁的零声子线和声子边带发光。Ce^(3+)→Cr^(3+)的能量传递是增强红光发射的重要方式,在YAG:Ce^(3+),Cr^(3+)体系中,由发射光谱得到的Cr^(3+)的红光与Ce^(3+)黄光发射强度的比值(I2/I1)与通过寿命测量得到的强度比很好符合。YAG:Ce^(3+),Pr^(3+),Cr^(3+)体系中,在只有Ce^(3+)离子被激发的状态下(λ(ex)=340nm),3种能量传递过程同时存在:Ce^(3+)→Pr^(3+)、Ce^(3+)→Cr^(3+)和Pr^(3+)→Cr^(3+),进一步增加了红光比例。利用这两种荧光粉和460nm蓝光发射管芯封装得到的白光LED,在正向驱动电流为20mA时,LED的显色指数分别为80.4和81.4。
Triply doped Y_3Al_5O_(12):Ce~(3+),Pr~(3+),Cr~(3+)phosphors with Ce~(3+)and Pr~(3+)substituting for Y~(3+)sites and Cr~(3+)substituting for Al~(3+)site are prepared by solid state reaction.A broad emission spectrum composed a yellow emission band from Ce~(3+),a light red emission line from Pr~(3+)and a deep red emission line from Cr~(3+), which are generated through energy transfer among the dopant ions.The study of photoluminescence and fluorescence decay indicates that there exist energy transfers from Ce~(3+)→Cr~(3+)and Ce~(3+)→Pr~(3+)→Cr~(3+).The effect of energy transfer on relative intensities of the three emissions is analyzed.A white LED is fabricated using a blue LED chip coated with the triply doped phosphor and shows a color rendering index of 81.4 and 80.4, respectively.It is higher than that either using Ce~(3+)and Cr~(3+)doubly doped phosphor or Ce~(3+)singly doped phosphors.