Pr3+掺杂Na5Lu9F32单晶发光性能的优化（英文）

应用坩埚下降法生长了Pr^3+离子掺杂的Na5Lu9F32单晶体.系统地研究了Pr^3+掺杂的Na5Lu9F32单晶的吸收光谱、荧光光谱和荧光衰减曲线.应用Judd-Ofelt理论分析计算了其光学强度等参数,结果表明Pr^3+离子处于Pr-F强共价键的高对称环境中.在440nm光的激发下观察到以482、523和605nm为中心的尖锐的强荧光发射带.研究了Pr^3+掺杂浓度对上述发光强度的影响规律,实验发现当Pr^3+掺杂浓度达到~0.5mol%时,其荧光发射强度达到最大.分析了环境温度从298K到443K变化时对荧光强度的影响,随着温度的增加,荧光强度逐步变弱,且其523nm的绿光受温度影响要小于482nm的蓝光和605nm的红光.

Efficient up-conversion Yb3+, Er3+ co-doped Na5Lu9F32 single crystal for photovoltaic application under solar cell spectrum excitation

Yb^3+/Er^3+co-doped Na5Lu9F32 single crystals used as a spectral up-converter to improve the power conversion efficiency of perovskite solar cells are prepared via an improved Bridgman approach. Green and red up-conversion(UC) emissions under the excitation of near-infrared(NIR) bands of 900–1000 nm and1400–1600 nm can be observed. The effectiveness of the prepared materials as a spectral converter is verified by the enhancement of power conversion efficiency of perovskite solar cells. The sample with a UC layer is 15.5%more efficient in converting sunlight to electricity compared to the UC layer-free sample due to the absorption of sunlight in the NIR range. The results suggest the synthesized Yb^3+/Er^3+co-doped Na5Lu9F32 single crystals are suitable for enhancing the performance of perovskite solar cells.

Investigation of the growth and optical properties of a Co^2＋-doped Na5Lu9F(32) single crystal

A 0.1 mol.% CoF2-doped Na5Lu9F（32）single crystal with high quality in the size of -φ10 mm×100 mm was grown by the Bridgman method. Three peaks located at 504, 544, and 688 nm and a broad band in the range of 1200–1600 nm centered at 1472 nm were observed in the absorption spectra. The absorption peak position suggests cobalt ions in the divalent state in the grown crystal. Moreover, the cobalt ions are confirmed to locate in the distorted cubic crystal structure. Upon excitation of 500 nm light, a sharp emission peak at 747 nm ascribed to the ^2T2（H1） →^4A2（F） transition was observed for the crystal. The Co^2＋-doped Na5Lu9F（32）crystal shows a potentially promising material for the application of a passively Q-switched laser operating in the near-infrared range.

Er^(3+)掺杂Na_5Lu_9F_(32)单晶体的红外光学特性

采用坩埚下降法成功地生长了Er^(3+)离子掺杂的Na_5Lu_9F_(32)(NLF)单晶体。测定了单晶体在400~2 500nm波段的吸收光谱与2.5~25μm红外波段的透过光谱。Na_5Lu_9F_(32)单晶体在400~7 150 nm宽波段范围具有好的光学透过性,在该波段的透过率达到90%。在透过光谱中几乎观察不到2.7μm中红外波段的吸收,说明单晶体中OH^-离子的含量极低。根据测定的吸收光谱,通过Judd-Ofelt理论计算了Er^(3+)在单晶体中的光学强度参数Ω_t(Ω_2=2.08,Ω_4=2.07,Ω_6=0.75),以及相应的辐射跃迁速率、荧光分支比和荧光寿命。根据Futchbauer-Ladenburg公式估算了样品的发射截面大约分别为1.42×10^(-20)cm^2(~4I_(13/2)→~4I_(15/2))和1.66×10^(-20)cm^2(~4I_(11/2)→~4I_(13/2))。在980 nm半导体激光器(LD)激发下,研究了单晶体的近红外1.5μm与中红外2.7μm的发射光谱特性。

Tm^(3+)掺杂Na_5Lu_9F_(32)单晶体的1.8μm优化发射性能研究（英文）

采用改进过的布里奇曼法成功地生长了Tm^(3+)离子浓度从0.5~4mol%变化的高质量Na_5Lu_9F_(32)单晶.在790nm LD激发下,研究了不同Tm^(3+)掺杂晶体在1.86μm波段的荧光发射性能、衰减曲线以及Tm^(3+)离子之间的能量传递过程.当Tm^(3+)离子掺杂浓度增加到~1.95mol%时,晶体在1.86μm处的荧光发射强度达到最大.然后,随着Tm^(3+)离子浓度进一步的增大,发射强度迅速下降.然而,Tm^(3+)离子在3F4能级处的荧光寿命随着Tm^(3+)掺杂浓度从0.5增加到4mol%,逐渐降低.同时计算了1.86μm处最大的受激发射截面为0.80×10^(-20) cm^2.Tm^(3+)离子的浓度猝灭效应和离子之间的交叉弛豫能量传递过程是造成1.86μm荧光发射变化的主要原因.