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liloveyan

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虫号: 1013555
注册: 2010-05-07
专业: 无机材料化学

[交流] down-conversion in Er3+/Yb3+ co-doped YF3

Abstract ：Er3+/Yb3+ co-doped YF3 powder is prepared by combining a nitrate decomposition method with a NH4HF2 fluorization process, from which efficient energy transfer induced down-conversion is achieved. An absorbed 365 nm
near ultraviolet photon is split into two photons of 650 nm red and 1000 nm near infrared radiations, both falling in the responding region of Si-based solar cells. The quantum cutting mechanism has been proposed and discussed and the energy transfer efficiency for the quantum cutting is evaluated by developing an emission intensity ratio contrast method. The investigation might offer a new possible approach to achieve Si-based solar cells of high efficiency by down-converting the near ultraviolet part of the solar spectrum. Quantum cutting (QC) was firstly reported in Pr3+ doped YF3 and NaYF4 phosphors in the early 1970s [1, 2]. It could generate two low-energy photons from an absorbed incident high energy photon, by which the necessary redshift of the absorbed radiation is obtained without losing energy efficiency.This is considered as an exciting scenario toward the development of superior luminescent materials and devices After that, QC has also been witnessed in other materials doped with a single rare earth ion such as Pr3+, Tm3+and Gd3+。The QC down-conversion based on an ion-couple was
firstly reported in LiGdF4 phosphor byWegh [5], of which a vacuum ultraviolet photon is absorbed by Gd3+ and two red photons are then emitted by Eu3+ ions. Thereafter, many people attached great importance to QC by the combination
of two or even three ions such as Er3+ → Gd3+ [6],
Gd3+→Tb3+ [7], Pr3+→Mn2+ [8], Pr3+→Cr3+ [9] and
Er3+ → Gd3+ → Tb3+ [10]. In these cases, the absorbed
energy of the donor ions is transferred stepwise to the acceptor
ions, and two photons of low energy are obtained.
These QC phosphors can enhance luminescence emission in
the visible region and have important applications in more
efficient plasma display panels and mercury-free fluorescent
tubes.
Recently, near infrared QC performed by cooperative energy
transfers has been reported, which is also based on the
combination of two ions [11–14]. In Tb3+ and Yb3+ codoped
YPO4 [11], for instance, a cooperative energy transfer
from Tb3+ to two Yb3+ ions leads to the photon doubling
in the near infrared region. Similar phenomena have
also been observed in several other rare earth coupled systems
such as Pr3+
/Yb3+ [12], Tm3+
/Yb3+ [12, 13] and
Ce3+
/Yb3+ [14] co-doped crystals or glasses. These phosphors
can convert 484, 489, 475, and 330 nm photons into
doubled 1000 nm photons, respectively. Since the energy of
the converted photons is just above the band edge of crystalline
Si, the energy losses by thermalization of electron
hole pairs are minimized. Therefore, near infrared QC induced
by cooperative energy transfer can enhance the energy
efficiency of silicon-based solar cells in theory, which
has attracted intense attention.

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