Carrier recombination processes and divalent lanthanide spectroscopy inYPO4:Ce3+;L3+

Abstract

We studied charge carrier trapping, detrapping, and recombination phenomena in Ce 3+ doped YPO 4 , codoped with Sm 3+ , Dy 3+ , or Tm 3+ . Ce ions trap the holes and Sm, Dy, and Tm trap electrons created during x-ray irradiation. By means of red to infrared stimulation, the trapped electrons can be back transferred to Ce leading to shorter wavelength Ce 3+ 5d-4f luminescence. Excitation spectra for this recombination luminescence were recorded from 10 K to room temperature. It provides information on the excited state energies of divalent Sm, Dy, and Tm with respect to the lanthanide ground state energy and with respect to the mobility edge energy of YPO 4 . From the temperature dependence, insight is obtained on the carrier recombination pathways. We will identify temperature independent tunneling recombination, recombination by thermal excitation to the conduction band, and phonon-assisted delocalization of electrons from impurity states within the conduction band.

Density Functional Characterization of the 4f‐Relevant Electronic Transitions of Lanthanide‐Doped Lu2O3 Luminescence Materials

“…For all of the doped rare‐earth ions, the level positions of 4 f ground state for divalent and trivalent lanthanides as function of the number of electrons in 4 f shells of Ln 3+ are summarized in Figure a, in which a characteristic double “zigzag” pattern for Ln 2+ and Ln 3+ states is figured out when lanthanide activators is introduced into Lu 2 O 3 host. This special energy level schemes for Ln 2+ and Ln 3+ ions by our theoretical calculations is in the same trend with the results reported by Dorenbos using empirical methods and experimental techniques . Meanwhile, the “zigzag” feature is independent on the type of host compound, therefore, the DFT+ U method can give suitable and correct results consistent with the experiment, and confirming the selection of Hubbard‐ U to lanthanide 4 f shell is reasonable.…”

Modeling the chemical shift of lanthanide4felectron binding energies

“…(9). Since U (6,A) can be determined routinely from optical spectroscopy on lanthanide-doped compounds, Eq.…”

“…Such a so-called host referred 4f -electron binding energy (4f -HRBE) scheme can be constructed routinely for many different compounds using relatively few experimental data as input. [7][8][9] The double zigzag curves connect the lanthanide 4f -HRBE as a function of the number of electrons in the 4f shell. The lower curve (in blue) pertains to the trivalent lanthanide ion and the upper curve (in red) to the divalent lanthanide ion.…”

Experimental insights on the electron transfer and energy transfer processes between Ce3+-Yb3+ and Ce3+-Tb3+ in borate glass

“…Both interactions are completely distinct from each other but sometimes occur simultaneously, thereby leading to the misinterpretation of physical processes. The basic difference between the two mechanisms is that the former depends on the absolute energy of the electron in donor and acceptor states, 15,18 whereas the later mechanism needs resonant condition of donor-acceptor electronic transitions. 17 Dorenbos explained the feasibility of electron transfer processes among lanthanide ions using the vacuum referred electron binding energy (VRBE) of dopant ions.…”