Unraveling electron liberation from Bi²⁺ for designing Bi³⁺-based afterglow phosphor for anti-counterfeiting and flexible X-ray imaging

Unraveling electron liberation from Bi²⁺ for designing Bi³⁺-based afterglow phosphor for anti-counterfeiting and flexible X-ray imaging

Lyu, T. (TU Delft RST/Luminescence Materials)
Dorenbos, P. (TU Delft RST/Luminescence Materials)
Li, Canhua (Huaqiao University, Xiamen)
Li, Silei (Huaqiao University, Xiamen)
Xu, Jian (National Institute for Materials Science)
Wei, Zhanhua (Huaqiao University, Xiamen)

2022

It is challenging to rational design persistent luminescence and storage phosphors with high storage capacity of electrons and holes after X-ray charging. Such phosphors have potential applications in anti-counterfeiting and X-ray imaging. Here we have combined vacuum referred binding energy diagram (VRBE) construction, photoluminescence spectroscopy, and thermoluminescence to study the trapping processes of charge carriers in NaYGeO₄. In NaYGeO₄:0.004Bi³⁺ and NaYGeO₄:0.004Bi³⁺,0.005Ln³⁺ (Ln = Tb or Pr), Bi³⁺ appears to act as a shallow electron trap, while Bi³⁺ and Ln³⁺ act as deep hole trapping and recombination centres. We will show how to experimentally determine the VRBE in the Bi^{2+ 2}P_1/2 ground state in NaYGeO₄ and NaLuGeO₄ by thermoluminescence study. The electron trap depth produced by Bi³⁺ codopant in NaLu_1-xY_xGeO₄:0.003Bi³⁺,0.008 Tb³⁺ can be adjusted, by increasing x, resulting in conduction band engineering. By combining Bi³⁺ as an electron trap and Bi³⁺ and Tb³⁺ as the hole traps, excellent X-ray charged afterglow phosphors were developed. The integrated TL intensity of the optimized NaYGeO₄:0.004Bi³⁺ and NaYGeO₄:0.003Bi³⁺,0.008Tb³⁺ after exposure to X-rays is about 4.5 and 1.1 times higher than that of the state-of-the-art BaFBr(I):Eu²⁺ storage phosphor. Intense initial Tb³⁺ 4f → 4f afterglow appears in NaYGeO₄:0.003Bi³⁺,0.008Tb³⁺ and more than 40 h afterglow is measurable in NaYGeO₄:0.004Bi³⁺ and NaYGeO₄:0.003Bi³⁺, 0.008 Tb³⁺ after X-ray charging. We will show proof-of-concept anti-counterfeiting and X-ray imaging applications by using the developed afterglow phosphors and CsPbI₃ quantum dots. This work not only provides experimental evidence on the VRBE in the Bi^{2+ 2}P_1/2 ground state in NaYGeO₄, but also shows how to design and develop good afterglow phosphors for anti-counterfeiting and X-ray imaging by deeply studying and controlling the trapping processes of charge carriers in bismuth and/or lanthanides doped inorganic compounds.

Bi VRBE
Bismuth
Electron liberation from Bi
Electron trap depth engineering
X-ray imaging

http://resolver.tudelft.nl/uuid:57cb2a92-5345-4747-97ec-8b9e1c5cd911

https://doi.org/10.1016/j.cej.2022.135038

2023-07-01

1385-8947

Chemical Engineering Journal, 435

Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

journal article

© 2022 T. Lyu, P. Dorenbos, Canhua Li, Silei Li, Jian Xu, Zhanhua Wei