Preparation And Downconversion Investigation Of Rare Earth Ions Doped Luminescence Materials

In this paper,BaGd₂ZnO₅: Dy³⁺, Yb³⁺ nanocrystal,BaGd₂ZnO₅:Nd³⁺, Yb³⁺, Gd（PO3）3: Ce³⁺, Yb³⁺ andBaGd₂ZnO₅: Ce³⁺, Yb³⁺ phosphors are prepared and analyzed. The photoluminescence spectra are measured, and the energy transfer mechanism is obtained by analyzing the enrgy level diagram. The luminescence decay curves are measured, and the energy transfer efficiency and quantum efficiency are calculated. The main contents and result as following:（1） BaGd₂ZnO₅: Dy³⁺, Yb³⁺ was successfully synthesized by sol–gel method. The crystal structure and morphology of the samples were characterized by the X-ray powder diffraction（XRD） and scanning electron microscope, and the diameter is around 500 nm. Under 3W 971 nm near-infrared laser excitation, the dependence of the up-conversion emission intensities of the phosphors on the working power of laser diode was obtained as an evidence for the energy transfer from Yb³⁺ to Dy³⁺, and the blue, green and near-infrared emission photons are obtained. Furthermore, under 354 nm excitation, the emission spectra from visible to near-infrared are measured. Then, the down-conversion energy transfer process from Dy³⁺ to Yb³⁺ are analyzed by the energy level diagram, and the near-infrared quantum cutting between Dy³⁺ and Yb³⁺ are proved. Furthuremore, the lifetime decay curves are measured, and the highest quantum efficiency calculated is 158.0%.（2）BaGd₂ZnO₅:Nd³⁺, Yb³⁺ were synthesized by the high temperature solid-state method. The phase and structure have been investigated by the X-ray powder diffraction. By analyzing the excitation and emission spectra and energy level diagram, it indicates that the energy transfer from Nd³⁺ to Yb³⁺ occurs. The luminescen decay curves are measured, and the maximum of energy transfer efficiency is 31.9% without the consideration of concentration quenching.（3） Ce³⁺, Yb³⁺ codoped Gd（PO₃）₃ phosphors were synthesized by the high temperature solid-state method. The phase and structure have been investigated by the X-ray powder diffraction. In order to study the energy transfer mechanism between Ce³⁺（sensitizer） and Yb³⁺（activator）, the excitation spectra and decay curves are measured, and the cooperative quantum cutting are proved. The highest quantum efficiency calculated by the lifetime is 123.7%. With access to broad-band absorption, narrow-band emission as well as high energy transfer efficiency, Ce³⁺ and Yb³⁺ codoped Gd（PO₃）₃ phosphors may have potential applications in modifying the solar spectrum to enhance the efficiency of silicon solar cells.（4）BaGd₂ZnO₅: Yb³⁺ was successfully synthesized by sol–gel method. Then, in order to prove the energy transfer mechanism, Er³⁺ and Yb³⁺ co-dopedBaGd₂ZnO₅ phosphors, and Ce³⁺, Yb³⁺ co-dopedBaGd₂ZnO₅ phosphors are prepared by the same method, and the phase and structure have been investigated by the X-ray powder diffraction. The excitation and emission spectra are measured. Furthermore, the comparison of the excitation spectra ofBaGd₂ZnO₅: Yb³⁺ andBaGd₂ZnO₅: Er³⁺,Yb³⁺ have been done, and the efficient energy transfer fromBaGd₂ZnO₅ host to Yb³⁺ is proved. After doping Ce³⁺ inBaGd₂ZnO₅:Yb³⁺, the broad-band excitation spectrum from 230 nm to 400 nm is obtained, and the excitation peaks round 261 nm and 312 nm are observed. The broadened excitation spectra can be attributed that the addition of Ce³⁺ ion changes the crystal field around the host.