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Upconversion Mechanism in Er3+ Doped Perovskite

Author: DiDi
Tutor: ZhengYangDong
School: Harbin Institute of Technology
Course: Optics
Keywords: upconversion perovskite nano-crystal rare-earth ion doping energy transfer
CLC: TB383.1
Type: Master's thesis
Year: 2009
Downloads: 34
Quote: 0
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Abstract


Perovskite is a kind of important inorganic functional material for its high Permittivity, good property of insulation, perfect physical and chemical stability and transparency of light wave in visible range. Further more, perovskite material can be applied as a suitable substrate for rare-earth ions doping in the research of upconversion(UC). So Er3+ doped and Er3+, Yb3+ co-doped CaTiO3 nano-crystal were synthesized by a improved solid-state method in this paper. Upconversion mechanism of Er3+ and Er3+, Yb3+ systems in CaTiO3 was investigated, when pumping with 974nm LD.Er3+ doped CaTiO3 nano-crystal has a strong emissions in the green band under the pumping of 974nm LD. However, there is almost no red emission in the red band. The reason is that Ca2+ ions are substituted by the Er3+ ions doping into CaTiO3 lattice, so Er3+ ions are wrapped by the cage-like structure made up by group of Ti4+ and O2- ions. Single band emissions of green UC fluorescence are observed, because of the inhibition of concentration vanishing while the increasing of Er3+ increasing. As the energy transmission is nearly forbidden in the substrate of CaTiO3, the red emissions will never be enhanced when the doping concentration is increased. The origin of the red emissions comes from the weak self-relaxtion and the contribution of multi-phonon process caused by the vibration of molecular attached in nano-crystal surface.In Er3+,Yb3+ co-doped system, green and red emissions are both enhanced with the increasing of Yb3+ concentration, under the pumping of 974nm LD. And addition of Yb3+ ions has a more obviously increment to the red emissions. It is thought that besides the sensitization of the upconversion, Yb3+ can affect the population of red emission level by the energy transmit back (EBT) process between Er3+ ions and Yb3+ ions. EBT process can complete the path to fill 4F9/2 level by population 4I13/2 level of Er3+. However, 4F9/2 level can still not be full populated, because of the restriction from CaTiO3 lattice that inhibit the energy transmission between ions.

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