Issue 2, 2018

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

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

Supplementary files

Article information

Article type
Paper
Submitted
15 nov 2017
Accepted
06 dec 2017
First published
06 dec 2017

J. Mater. Chem. C, 2018,6, 369-379

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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