Discovering UV-light or X-ray charged afterglow and storage phosphors with high charge carrier storage capacity remains challenging. Herein, a method is proposed by combining vacuum referred binding energy (VRBE) diagram construction and optimization of dopants’ concentration and compound synthesis. The refined chemical shift model, optical spectroscopy, and thermoluminescence will be combined to construct the VRBE diagram of LiTaO3 with the lanthanide and bismuth charge transition levels. Based on the constructed VRBE diagram of LiTaO3, Bi3+, and/or Ln3+ (Ln = Tb or Pr) doped LiTaO3 will be studied. By combining Bi3+ with Tb3+, Pr3+, or Bi3+ itself, Bi3+ emerges to act as a ≈0.62 eV deep electron trap, while Tb3+, Pr3+, or Bi3+ acts as about 1.5 eV deep hole capturing and recombination centres. The VRBE in the Bi2+ 2P1/2 ground state will be derived by thermoluminescence study. Proof-of-concept X-ray imaging, compression force distribution monitoring, and color-tailoring for anti-counterfeiting will be demonstrated by using the developed Bi3+ and/or Ln3+ doped LiTaO3. This work promotes the understanding of trap level locations and on the trapping and release processes of charge carriers in Bi3+ and/or lanthanides doped inorganic compounds for rational design of new afterglow and storage phosphors.@en

Developing X-ray or UV-light charged storage and mechanoluminescence (ML) materials with high charge carrier storage capacity is challenging. Such materials have promising utilization in developing new applications, for example, in flexible X-ray imaging, stress sensing, or non-real-time recording. Herein, the study reports on such materials; Bi3+, Tb3+, Ga3+, or Ge4+ doped LiTaO3 perovskite storage and ML phosphors. Their photoluminescence, thermoluminescence (TL), and ML properties are studied. The charge carrier trapping and release processes in the Bi3+, Tb3+, Ga3+, or Ge4+ doped LiTaO3 are explained by using the constructed vacuum referred binding energy diagram of LiTaO3 including the energy level locations of unintended defects, Tb3+, Bi3+, and Bi2+. The ratio of the TL intensity after X-ray charging of the optimized LiTaO3:0.005Bi3+,0.006Tb3+,0.05Ga3+, or LiTaO3:0.005Bi3+,0.006Tb3+,0.05Ge4+ to that of the state-of-the-art BaFBr(I):Eu2+ is ≈1.2 and 2.7, respectively. Force induced charge carrier storage phenomena is studied in the Tb3+, Bi3+, Ga3+, or Ge4+ doped LiTaO3. Proof-of-concept compression force distribution sensing and X-ray imaging is demonstrated by using optimized LiTaO3:0.005Bi3+,0.006Tb3+,0.05Ga3+ dispersed in a hard epoxy resin disc and in a silicone gel film. Proof-of-concept color-tailorable ML for anti-counterfeiting is demonstrated by admixing commercial ZnS:Cu+,Mn2+ with optimized LiTaO3:0.005Bi3+,0.006Tb3+,0.05Ge4+ in an epoxy resin disc.@en

Discovering energy storage materials with rationally controlled trapping and de-trapping of electrons and holes upon x-rays, UV-light, or mechanical force stimulation is challenging. Such materials enable promising applications in various fields, for instance in multimode anti-counterfeiting, x-ray imaging, and non-real-time force recording. In this work, photoluminescence spectroscopy, the refined chemical shift model, and thermoluminescence studies will be combined to establish the vacuum referred binding energy (VRBE) diagrams for the LiSc1-xLuxGeO4 family of compounds containing the energy level locations of Bi2+, Bi3+, and the lanthanides. The established VRBE diagrams are used to rationally develop Bi3+ and lanthanides doped LiSc1-xLuxGeO4 storage phosphors and to understand trapping and de-trapping processes of charge carriers with various physical excitation means. The thermoluminescence intensity of x-ray irradiated LiSc0.25Lu0.75GeO4:0.001Bi3+,0.001Eu3+ is about two times higher than that of the state-of-the-art x-ray storage phosphor BaFBr(I):Eu2+. Particularly, a force induced charge carrier storage phenomenon appears in Eu3+ co-doped LiSc1-xLuxGeO4. Proof-of-concept non-real-time force recording, anti-counterfeiting, and x-ray imaging applications will be demonstrated. This work not only deepens our understanding of the capturing and de-trapping processes of electrons and holes with various physical excitation sources, but can also trigger scientists to rationally discover new storage phosphors by exploiting the VRBEs of bismuth and lanthanide levels.@en

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.@en

Multimode luminescence relates to how charge carriers are transported and recombined in response to various physical excitations. It shows promising applications in many fields like advanced anti-counterfeiting, information storage and encryption. Enabling a stable single compound with multimode luminescence is a unique technology but still remains a challenge. Herein, a versatile and high-performance energy storage LiTaO3:0.01Tb3+,xGd3+ perovskite is discovered by utilizing the interplay of electron-trapping defect levels and hole-trapping Tb3+. It combines an excellent charge carrier storage capacity (≈7 and 12 times higher than state-of-the-art BaFBr(I):Eu2+ and Al2O3:C), >1200 h storage duration, >40 h afterglow, efficient optically stimulated luminescence, persistent mechanoluminescence, and force-induced charge carrier storage features. Particularly, it well responds to various stimuli channels, i.e., wide-range X-rays to 850 nm infrared photons, thermal activation, mechanical force grinding, or compression. To elucidate this multimode luminescence, charge carrier trapping and release processes in LiTaO3:0.01Tb3+,xGd3+ with various physical stimulations will be unraveled by combining the vacuum-referred binding diagram construction, spectroscopy, thermoluminescence, and mechanoluminescence techniques. The versatile and high-performance LiTaO3:0.01Tb3+,xGd3+ enables promising proof-of-concept multimode luminescence applications in advanced anti-counterfeiting, flexible X-ray imaging, continuous compression force sensing, and non-real-time recording.@en

Developing X-ray charged dosimeters with excellent charge carrier storage capacity and stability is challenging. Such energy storage dosimeters have fascinating use in developing novel applications, for instance, in radiation detection, advanced multimode anti-counterfeiting, and flexible X-ray imaging of curved objects. Herein, novel LiTaO3:Ln3+,Eu3+ (Ln = Tb or Pr) perovskite dosimeters are reported by combining the vacuum referred binding energy (VRBE) diagram of LiTaO3 and the optimization of dopant's concentration and compound synthesis condition. Based on the VRBE diagram prediction, charge carrier capturing and de-trapping processes in Eu3+ and/or Ln3+ (Ln = Tb or Pr) doped LiTaO3 will be studied to unravel the role of Eu3+ as a good electron trapping centre and to discover a record storage phosphor. The ratios of the thermoluminescence intensity of the optimized LiTaO3:0.005Tb3+,0.001Eu3+ to that of the state-of-the-art BaFBr(I):Eu2+, Al2O3:C, or NaLuF4:Tb3+ are 5.2, 8.8, or 2.8, respectively. The charge carriers can be stored more than 1000 h in LiTaO3:0.005Tb3+,0.001Eu3+. Proof-of-concept anti-counterfeiting application will be demonstrated by combining the colour-tailorable photoluminescence, afterglow, thermally, or optically stimulated luminescence in LiTaO3:0.005Tb3+,xEu3+ and LiTaO3:0.005Pr3+,0.001Eu3+. Multimode anti-counterfeiting application will be proposed by combining a high absolute X-ray scintillation light yield of 19000 ± 1800 ph/MeV of LiTaO3:0.005Tb3+,0.001Eu3+. Proof-of-concept flexible X-ray imaging application will be demonstrated by using the optimized LiTaO3:0.005Tb3+, 0.001Eu3+ dispersed in a silicone gel film.@en

Discovering bismuth based smart materials that can respond to thermal, mechanical, and wide range X-ray to infrared photon excitation remains a challenge. Such materials have various uses like in advanced information encryption. In this work, valence state change between Bi2+, Bi3+, and Bi4+, and the dual role of Bi3+ in trapping electrons and holes have been studied in Bi3+ or/and Ln3+ (Ln=Tb or Pr) doped LiScGeO4 family of compounds by vacuum referred binding energy (VRBE) diagram construction, thermoluminescence, and spectroscopy. Electron release from Bi2+ has been evidenced. It can be used to experimentally determine the VRBE in the Bi2+ 2P1/2 ground state and to realize Bi3+ negative quenching luminescence. Particularly, a new force induced charge carrier storage phenomenon has been discovered for non-real-time force recording. Wide range of emission tailorable afterglow, unique Bi3+ ultraviolet-A, white, and infrared afterglow have been demonstrated by using Bi3+ as a hole trapping and recombination center and using energy transfer processes from Bi3+ to Tb3+, Pr3+, Dy3+, or Cr3+. Proof-of-concept advanced anti-counterfeiting, information encryption, and X-ray imaging will be demonstrated. This work not only develops smart storage phosphors, but more importantly unravels the valence change between Bi2+, Bi3+, or Bi4+ and how it can affect the trapping and release of charge carriers with thermal, optical, or mechanical excitation. This work therefore can promote the discovery and development of Bi3+ based smart materials for various applications.@en