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Issue 2, 2018
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Charge carrier trapping processes in lanthanide doped LaPO4, GdPO4, YPO4, and LuPO4

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Abstract

Various methods for deliberate design of electron and hole trapping materials were explored with a study on double lanthanide doped rare earth ortho phosphates. Cerium acts as a recombination center, while lanthanide codopants act as electron trapping centers in LaPO4:0.005Ce3+,0.005Ln3+. The electron trap depth generated by lanthanide codopants can be tailored by the choice of lanthanide, and for a fixed set of lanthanide dopants like in Gd1−xLaxPO4:0.005Ce3+,0.005Ho3+ solid solutions, by changing x, leading to conduction band (CB) engineering. Herein, the electrons liberated from Ho2+ recombined through the conduction band at Ce4+ to yield Ce3+ 5d–4f emission. In contrast, samarium, europium and ytterbium act as recombination centers, while Tb3+ and Pr3+ act as hole trapping centers in double lanthanide doped YPO4, as Tb3+ and Pr3+ codopant recombination is realized via hole release rather than the more commonly reported electron release. The holes recombine via the valence band with the electrons trapped in Yb2+, Sm2+, or Eu2+ to generate 4f–4f luminescence from Yb3+, Sm3+, or Eu3+. Lu3+ was introduced in YPO4 to tailor the valence band (VB) energy and to tune the hole trap depths of Tb3+ and Pr3+ in Y1−xLuxPO4:0.005Ln3+ solid solutions. Our results shed light on the deliberate design of electron and hole trapping materials based on a deep understanding of trap level locations and on the transport and trapping processes of charge carriers.

Graphical abstract: Charge carrier trapping processes in lanthanide doped LaPO4, GdPO4, YPO4, and LuPO4

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Supplementary files

Article information


Submitted
15 Nov 2017
Accepted
06 Dec 2017
First published
06 Dec 2017

J. Mater. Chem. C, 2018,6, 369-379
Article type
Paper

Charge carrier trapping processes in lanthanide doped LaPO4, GdPO4, YPO4, and LuPO4

T. Lyu and P. Dorenbos, J. Mater. Chem. C, 2018, 6, 369
DOI: 10.1039/C7TC05221A

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