It is challenging to obtain a material that can detect photons ranging from X-rays to infrared light. Such materials have promising use to develop advanced applications like in information storage, anticounterfeiting, or X-ray imaging. This article reports on such a material; LiTaO₃:xBi³⁺,yDy³⁺ perovskite phosphor. Experimental spectroscopy, thermoluminescence, and vacuum referred binding energy diagram (VRBE) construction are combined to study the trapping processes of charge carriers. The VRBEs in the ground or excited states of Bi³⁺ and Bi²⁺ are discussed. Bi³⁺ emerges to act as a ≈1.3 eV deep hole capturing center and it may possibly also act as a 0.80 ± 0.5 eV deep electron trapping center. A linear relation between the amount of stored charge carriers and a photochromic phenomenon both induced by X-rays or 254 nm UV-light charging appears. The stored charge carriers in LiTaO₃:xBi³⁺,yDy³⁺ are removed by heating or with an optically stimulated process with 365 nm UV light to 850 nm infrared laser. More than 3 or 40 h of Bi³⁺ and Dy³⁺ based white afterglow is measurable in LiTaO₃:0.005Bi³⁺,0.004Dy³⁺ after exposure to X-rays or 254 nm UV light. Proof-of-concept light detection applications like 2D information storage and anticounterfeiting or X-ray imaging are demonstrated by using the phtotochromic and white afterglow LiTaO₃:xBi³⁺,yDy³⁺ phosphors.

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.