Synthesis And Iuminescence Properties Of CaFCl:Tb³⁺,Yb³⁺ Nanoparticles

The luminescent properties of CaFCl:Tb3+have been investigated in this paper. Our research is important for the study of green phosphors suitable for ultraviolet LED chips. Moreover, the quantum cutting of CaFCl:Tb3+,Yb3+was realized for the first time, which can provide potential applications for the enhancement of photoelectric conversion efficiency of silicon solar cells.1. The CaFCl:Tb3+nanoparticles were prepared by the one-step sol-gel method, which was reported for the first time. High efficient emissions that originated from Tb3+ions were observed under the376nm excitation. Moreover, the luminescence intensity increases with increasing Tb3+concentration until the concentration rises to25%. The CaFCl:Tb3+@SiO2nanoparticles were prepared by the Stober method. The best coating conditions were acquired:the volume ratio between ethylalcohol and isopropanol was1:10, the volume of ammonium hydroxide and tetraethoxysilane were0.06ml and0.03ml, respectively. A broad band of amorphous SiO2was observed in the XRD patterns. The transmission electron microscope (TEM) demonstrated the SiO2was successfully coated to the surface of the CaFCl. The SiO2coating not only prevented the samples from deliquescing and but strengthened the emission intensity of the samples.2. Charge compensations were introduced to optimize luminescence of the sample. A series of CaFCl:Tb3+, A+(A=Li, Na and K) nanoparticles were synthesized by the sol-gel method. The luminescent properties of the samples were studied by measuring excitation and emission spectra of the CaFCl:Tb3+, A+. The possible reasons why oxygen defects OF existing in the CaFCl were discussed. The effect of charge compensators A+(A=Li, Na and K) co-doped with Tb3+in CaFCl was investigated. All the charge compensators weaken the emission of defects. Furthermore, Li+ion was the best charge compensator, because it not only reduced the emission of defects but also increased the emission intensity of Tb3+ion.3. The CaFCl:25%Tb3+,x%Yb3+nanoparticles were prepared via the sol-gel method and the luminescent properties of the samples were investigated. Infrared quantum cutting involving Yb3+950-1050nm (2F5/2â†'2F7/2) emission was acquired under the excitation of5D4energy level of Tb3+at484nm. Besides, excitation spectrum that originated from Tb3+ions and defects was detected under the986nm emission. The above results indicated the evidence for cooperative energy transfer from Tb3+to Yb3+ions. Moreover, the emission intensity of Yb3+reached its strongest when the doping concentration was40%. In addition, the CaFCl:25%Li+,25%Tb3+,10%Yb3+nanoparticles were synthesized by the same method, and the luminescent properties of the samples were also studied. Comparing the excitation spectrum of Tb3+with Li+doping, the excitation of defects was weakened under986nm emissions. Doping Li+not only optimized the luminescence performance but also improved the luminous efficiency of the samples.