Multimodal Luminescence Research Articles

Enhancement of NIR-II Emission of Er3+ by Doping Fe3+ in Double Perovskites: Multimode Luminescence for Versatile Optoelectronic Applications.

Erbium ions are commonly used to extend the photoelectric properties of metal halide perovskites from visible to near-infrared range. However, achieving high-efficiency multimode luminescence in a single system is difficult due to the weak absorption associated with forbidden 4f-4f transitions. In this study, a unique strategy is proposed to adjust multimode luminescence and enhance the second near-infrared region (NIR-II) emission in Cs2NaBiCl6 by incorporating Fe3+ ions. The as-prepared material demonstrates reversible thermochromism, driven by strong electron-phonon coupling effect, and exhibits tunable luminescence that can be adjusted by altering excitation energy and temperature. Notably, benefitting from the charge transfer transition of Fe3+-Cl- along with the influence of Fe3+ doping on the geometrical and electronic structures, the blue-excitable (450 nm) NIR-II emission around 1541 nm from Er3+ is realized for the first time, achieving an intensity 16.7 times higher and a maximum photoluminescence quantum yield (PLQY) of 22.5 %. This enhancement enables innovative applications such as two-dimensional information encryption by the multi-channel cooperative responses and improved NIR imaging. The study highlights the potential of Fe3+ doping in optimizing absorption and multimode luminescence in perovskites, opening avenues for advanced applications in blue-excitable NIR light emitting diodes (LEDs), thermometer, anti-counterfeiting, and NIR imaging.

Enhancement of NIR‐II Emission of Er3+ by Doping Fe3+ in Double Perovskites: Multimode Luminescence for Versatile Optoelectronic Applications

AbstractErbium ions are commonly used to extend the photoelectric properties of metal halide perovskites from visible to near‐infrared range. However, achieving high‐efficiency multimode luminescence in a single system is difficult due to the weak absorption associated with forbidden 4f‐4f transitions. In this study, a unique strategy is proposed to adjust multimode luminescence and enhance the second near‐infrared region (NIR‐II) emission in Cs2NaBiCl6 by incorporating Fe3+ ions. The as‐prepared material demonstrates reversible thermochromism, driven by strong electron‐phonon coupling effect, and exhibits tunable luminescence that can be adjusted by altering excitation energy and temperature. Notably, benefitting from the charge transfer transition of Fe3+‐Cl− along with the influence of Fe3+ doping on the geometrical and electronic structures, the blue‐excitable (450 nm) NIR‐II emission around 1541 nm from Er3+ is realized for the first time, achieving an intensity 16.7 times higher and a maximum photoluminescence quantum yield (PLQY) of 22.5 %. This enhancement enables innovative applications such as two‐dimensional information encryption by the multi‐channel cooperative responses and improved NIR imaging. The study highlights the potential of Fe3+ doping in optimizing absorption and multimode luminescence in perovskites, opening avenues for advanced applications in blue‐excitable NIR light emitting diodes (LEDs), thermometer, anti‐counterfeiting, and NIR imaging.

Lead‐free Halide Perovskites With ≈100% PLQY and Dual‐Color Emission for White Light‐Emitting Diodes

AbstractLead‐free halide perovskites (LHP) have attracted extensive attention in the field of next‐generation solid‐state lighting. However, single perovskite phosphor with tunable white‐light emission and ultra‐high photoluminescence quantum yield (PLQY) are rare. Here, the tunable dual‐color emission LHP phosphor is developed with a near‐unity PLQY of 99.5%. The LHP phosphor comprises Cs2NaInCl6: Sb3+/Bi3+ and Cs2InCl5·H2O: Sb3+/Bi3+ crystals, with the transition between these two perovskite structures being adjustable by the concentration of Na+. The addition of NaCl inhibits the hydrolysis of the [Sb(H2O)Cl5]2− octahedron, resulting in 3D connected [SbCl6]3− octahedron with less Jahn‐Teller distortion, and the PLQY of LHP is greater than 90%. Finally, the white‐light diode device is fabricated by assembling the LHP with a ultraviolet light‐emitting diode chip and the white light‐emitting diode device achieved Commission Internationale de l'Eclairage color coordinates of (0.34, 0.33), correlated color temperature of 4936 K, and a high color rendering index of 92.9. The LHP perovskite exhibited multimodal luminescence when excited by 365, 335, and 310 nm UV light, showing the multi‐mode anti‐counterfeiting capabilities of the LHP crystals.

Multimode Luminescence Tailoring in PMA4Na(In,Sb)Cl8 Organic–inorganic Hybrid Metal Halide via Rigid Benzene Ring Induced Local Lattice Distortion

AbstractLow dimensional organic‐inorganic hybrid metal halide materials have attracted extensive attention due to their superior optoelectronic properties. However, low photoluminescence quantum yields (PLQYs) caused by parity‐forbidden transition hinder their further application in optoelectronic devices. Herein, a novel yellow‐emitting PMA4Na(In,Sb)Cl8 (C7H10N+, PMA+) low‐dimensional OIMHs single crystal with a PLQY as high as 88 % was successfully designed and synthesized, originating from the fact that the doping of Sb3+ effectively relaxes the parity‐forbidden transition by strong spin‐orbit (SO) coupling and Jahn‐Teller (JT) interaction. The as‐prepared crystal shows an efficient dual emission peaking 495 and 560 nm at low temperature, which are ascribed to different levels of 3P1→1S0 transitions of Sb3+ in [SbCl6]3− octahedral caused by JT deformation. Moreover, wide‐range luminescence tailoring from cyan to orange can be achieved through adjusting excitation energy and temperature because of flexible [SbCl6]3− octahedral in the PNIC lattice. Based on a relative stiff lattice environment, the 560 nm yellow emission under 350 nm light excitation exhibits abnormal anti‐thermal quenching from 8 to 400 K owing to the suppression of non‐radiative transition. The multimode luminescence regulation enriches PMA4Na(In,Sb)Cl8 great potential in the field of optoelectronics such as temperature sensing, low temperature anti‐counterfeiting and WLED applications.

Opto/Thermoresponsive Multimode Luminescence in Eu- and Er-Activated CaF2 Phosphor for High-Security Anticounterfeiting.

As the landscape of information storage and security continues to evolve, the deployment of sophisticated anticounterfeiting strategies with robust security features and multimodal luminescent capabilities becomes imperative. In this work, Eu3+ and Er3+ ions are codoped into CaF2 phosphors to achieve multimodel optical output. The self-reduction of Eu3+ within the CaF2 matrix gives rise to the coexistence of Eu3+ and Eu2+ ions, which manifests as a color transition from orange to blue as the excitation wavelength is varied from 300 to 335 nm. Moreover, the distinct temperature-dependent behaviors of Eu3+ and Eu2+ ions underscore the material's visible temperature-sensitive luminescence properties, characterized by remarkable thermal sensitivity (Sa = 0.0156 K-1, Sr = 0.83%K-1). Additionally, the strategic introduction of Er3+ ions adds an extra dimension, enabling the realization of color-tunable upconversion luminescence through the fine-tuning of Er3+ concentration. This synergistic integration culminates in the establishment of an efficient three-path authentication model within the CaF2 host matrix, facilitating a dynamic multicolor response to changes in the excitation wavelength and temperature. By harnessing these diverse luminescent modalities, the study delivers a versatile and potent anticounterfeiting solution, advancing the frontiers of information security.

Time-Responsive Visualization of Cryogenic Detection Based on the Dynamic Optical Signals of CaZnOS.

Cryogenic detection technology is essential to ensure safety and effectiveness in fields such as medical refrigeration, cold chain transport, and cryogenic bioengineering. In this paper, a time-responsive visual cryogenic detection strategy is developed based on the storage properties of CaZnOS: Pb2+, Pr3+ phosphors with shallow traps. Since the carrier release rate from the trap center receives the influence of ambient temperature and storage time, the storage time of the temperature-sensitive product can be determined by the different optical signals of CaZnOS: Pb2+, Pr3+ phosphors obtained under 980 nm laser irradiation. In addition, CaZnOS: Pb2+, Pr3+ phosphors with multimode luminescence enable time-responsive visual detection of ambient temperature under extreme conditions. This work not only demonstrates the potential of CaZnOS: Pb2+, Pr3+ phosphors for visual detection of temperature and time but also paves the way for the development of various applications relying on cryogenic monitoring.

Tunable multimode emissions of Yb3+/Er3+-doped rare-earth-based Cs2NaYCl6 double perovskite crystals for versatile applications

Lead-free halide double perovskite materials are gaining recognition because of their excellent optoelectronic performance. However, achieving multimode luminescence with tunable emission colors in single-component double perovskites remains a significant challenge. Understanding the mechanism of trivalent lanthanide-ion doping could provide a valuable solution. Herein, we report the synthesis of rare-earth-based Cs2NaYCl6 double perovskites using a hydrothermal method. Efficient visible to near-infrared down-shifting (DS) photoluminescence and green up-conversion (UC) emissions were realized by incorporating Er3+ ions with abundant energy levels into the hosts. Notably, the DS and UC emission colors could both be adjusted by further introducing Yb3+ ions that acted as sensitizers, and the photoluminescence was significantly enhanced due to the strong absorption at 980 nm. Spectral analysis revealed that the high compatibility of lanthanide ions with the rare-earth-based double perovskites and cross-relaxation processes played a key role in achieving modulated emission and multiple excitation modes. This study aimed to understand the photophysical mechanism of lanthanide-ion-doped double perovskites, as well as to highlight their ability to modulate emissions. Furthermore, this study expands the versatile applications of lanthanide-ion-doped double perovskites in the fields of high-security anti-counterfeiting, tissue imaging, and night-vision systems.

RGB-tricolor multimodal luminescence of Ce3+ and Mn2+ in Mg2Al4Si5O18 via site occupancy engineering for anticounterfeiting applications

Multimodal luminescent materials have shown important applications in anti-counterfeiting and information encryption, however, mostly difficult to adjust optical properties with the structure, which leads to relatively constant emission position and less selectable excitation wavelength. Herein, Ce3+ and Mn2+ co-doped Mg2Al4Si5O18 phosphors are designed for the applications in RGB-tricolor multimodal anti-counterfeiting. Due to site occupancies, energy transfer and different thermal behaviors of Ce3+ and Mn2+ emissions, the emitting color of Mg2Al4Si5O18: Ce3+, Mn2+ is rich and tunable with different excitation wavelengths, doping concentrations and temperatures. The site occupancies of Ce3+ and Mn2+ are clarified with crystal field analysis and in-depth into transitions energies of Ce3+ and Mn2+. The energy transfer mechanism between Ce3+ and Mn2+ is analyzed via Inokuti-Hirayama model. The difference of thermal stabilities of Ce3+ and Mn2+ emissions is interpreted with construction of vacuum referred binding energy scheme. The as-designed molds of information encryption and decryption with Mg2Al4Si5O18: Ce3+, Mn2+ phosphors demonstrate the potential applications in anti-counterfeiting. The work provides an effective way for exploring Ce3+ and Mn2+ doped phosphors with RBG-tricolor multimodal luminescence.

Facile synthesis, multimode and tunable luminescence, and multifunctional applications of rare earth ions activated lead-free double perovskite crystals

Lead-free double perovskites have gained recognition as top luminescent materials due to their environmental friendliness, high chemical stability, structural adjustability, and excellent photoelectric properties. However, the poor modulation of emission restricts their applications, and it is highly desirable to explore stable and efficient double perovskites with multimode luminescence and adjustable spectra for multifunctional photoelectric applications. Herein, the rare earth ions Ln3+ (Er3+ and Ho3+) doped Cs2NaYCl6:Sb3+ crystals were synthesized by a simple solvothermal route. The X-ray diffraction pattern (XRD), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and elemental mapping images demonstrate that the Sb3+, Er3+, and Ho3+ ions have been homogeneously incorporated into the Cs2NaYCl6 crystals. As anticipated, the emission spectra of Cs2NaYCl6:Sb3+/Ln3+ are composed of two bands. One broad blue band derives from self-trapped exciton (STE) in [SbCl6]3− octahedra while another group of emission peaks stems from the f-f transitions of Ln3+ ions. The emission colors of Cs2NaYCl6:Sb3+/Ln3+ phosphors can be tuned in a wide range by modulating the doping concentrations of Ln3+ ions. The efficient energy transfer from STE to Ln3+ is the key point to achieving the efficient and tunable emissions Cs2NaYCl6:Sb3+/Ln3+ samples. Interestingly, Cs2NaYCl6:Sb3+/Ln3+ can also exhibit characteristic up-conversion luminescence of Ln3+ under near-infrared (NIR) excitation besides the down-conversion luminescence, revealing that the materials may have potential applicability in multimode anti-counterfeiting and information encryption applications. Furthermore, the light emitting diodes (LEDs) assembled by Cs2NaYCl6:Sb3+ and Cs2NaYCl6:Sb3+/Ln3+ phosphors display dazzling blue, green, and red emissions under a forward bias current, which indicates that the as-obtained double perovskites materials may have great potential in solid-state lighting and optoelectronic devices.

Manipulation of Multimodal and Multicolor Luminescence via Interplay of Traps and Rare Earth Emission Centers in Calcium Tungstate.

Multimodal luminescence involves color-tunable and wavelength manageable photon emissions upon variable luminescence pathways in response to different external stimuli, which provides clear visualization and high-level confidentiality for information encryption technologies. Integrating multimodal luminescence into a single matrix is regarded as a feasible strategy but remains a big challenge. In this work, multimodal (photoluminescence, persistent luminescence, upconversion luminescence, and thermally stimulated luminescence) and multicolor luminescence (green, yellow, orange, pink to red) is achieved in CaWO4:Yb3+,Er3+,Eu3+ phosphor by employing an interplay of traps and rare earth emission centers. Bright emission in a wide color gamut is achieved dynamically in response to thermal disturbance and light illumination, which further allows for on-demand emission manipulation in space and time dimensions. The compatible coexistence of multiple rare earth emissive centers together with abundant photoactive traps contributes to the excellent integration of multimodal photon emissions in calcium tungstate. This work provides a good example of integrating multimodal luminescence into one single matrix and indicates potential in advanced high-level information encryption applications.

Multimode Luminesce Tailoring PMA4Na(In,Sb)Cl8 Organic-inorganic Hybrid Metal Halidevia Rigid Benzene Ring Induced Local Lattice Distortion.

Low dimensional organic-inorganic hybrid metal halide materials have attracted extensive attention due to their superior optoelectronic properties. However, low photoluminescence quantum yields (PLQYs) caused by parity-forbidden transition hinder their further application in optoelectronic devices. Herein, a novel yellow-emitting PMA4Na(In,Sb)Cl8 (C7H10N+, PMA+) low-dimensional OIMHs single crystal with a PLQY as high as 88% was successfully designed and synthesized, originating from the fact that the doping of Sb3+ effectively relaxes the parity-forbidden transition by strong spin-orbit (SO) coupling and Jahn-Teller (JT) interaction. The as-prepared crystal shows an efficient dual emission peaking 495 and 560 nm at low temperature, which are ascribed to different levels of 3P1 → 1S0 transitions of Sb3+ in [SbCl6]3- octahedral caused by JT deformation. Moreover, wide-range luminescence tailoring from cyan to orange can be achieved through adjusting excitation energy and temperature because of flexible [SbCl6]3- octahedral in the PNIC lattice. Based on a relative stiff lattice environment, the 560 nm yellow emission under 350 nm light excitation exhibits abnormal anti-thermal quenching from 8 to 400 K owing to the suppression of non-radiative transition. The multimode luminescence regulation enriches PMA4Na(In,Sb)Cl8 great potential in the field of optoelectronics such as temperature sensing, low temperature anti-counterfeiting and WLED applications.

Multi-mode luminescence anti-counterfeiting and visual iron(Ⅲ) ions RTP detection constructed by assembly of CDs&Eu3+ in porous RHO zeolite

Carbon dots (CDs)-based composites have shown impressive performance in fields of information encryption and sensing, however, a great challenge is to simultaneously implement multi-mode luminescence and room-temperature phosphorescence (RTP) detection in single system due to the formidable synthesis. Herein, a multifunctional composite of Eu&CDs@pRHO has been designed by co-assembly strategy and prepared via a facile calcination and impregnation treatment. Eu&CDs@pRHO exhibits intense fluorescence (FL) and RTP coming from two individual luminous centers, Eu3+ in the free pores and CDs in the interrupted structure of RHO zeolite. Unique four-mode color outputs including pink (Eu3+, ex.254 nm), light violet (CDs, ex.365 nm), blue (CDs, 254 nm off), and green (CDs, 365 nm off) could be realized, on the basis of it, a preliminary application of advanced information encoding has been demonstrated. Given the free pores of matrix and stable RTP in water of confined CDs, a visual RTP detection of Fe3+ ions is achieved with the detection limit as low as 9.8 μmol/L. This work has opened up a new perspective for the strategic amalgamation of luminous guests with porous zeolite to construct the advanced functional materials.

Sextuplet luminescence with dynamically variable color/brightness in chromium activated gallium-silicate solid solution in R3 space group

The development of dynamic multi-color luminescence is a tremendous challenge for anti-counterfeiting. Herein, we have successfully synthesized Cr3+ activated gallium-silicate base material systems as the effective luminescent materials responsive to multiple field stimulation, exhibiting sextuplet luminescence including photoluminescence, strong red persistent luminescence (PersL), photo/thermo stimulated luminescence (PSL/TSL), photo-stimulated PersL and up-conversion luminescence (UCL). The luminescence quenching temperature is also improved in Cr3+,Yb3+,Er3+ co-doping sample relatives to Cr3+ single-doping phosphor. Especially, when Er3+ and Yb3+ are co-doped into Cr3+ activated phosphor system, UV preirradiated phosphor not only demonstrates an additional UCL from Er3+ ions accompanied with red PSL from the Cr3+ under NIR laser irradiation, but also leads to a dynamic change in color/brightness under the extension of NIR laser irradiation time. The multimode luminescence mechanisms are also proposed. Based on excellent luminescence characteristics, multi-color and multi-mode anti-counterfeiting patterns have been designed, especially appearing of dynamic anti-counterfeiting on luminescent color/brightness, which provides new dimensions for anti-counterfeiting technologies.

Enabling Multimodal Luminescence in a Single Nanoparticle for X-ray Imaging Encryption and Anticounterfeiting.

Multimodal luminescent materials hold great promise in a diversity of frontier applications. However, achieving the multimodal responsive luminescence at the single nanoparticle level, especially besides light stimuli, has remained a challenge. Here, we report a conceptual model to realize multimodal luminescence by constructing both mechanoluminescence and photoluminescence in a single nanoparticle. We show that the lanthanide-doped fluoride nanoparticles are able to produce excellent mechanoluminescence through X-ray irradiation, and color-tunable mechanoluminescence becomes available by selecting suitable lanthanide emitters in a core-shell-shell structure. Furthermore, the design of a multilayer core-shell nanostructure enables multimodal emissions including radioluminescence, persistent luminescence, mechanoluminescence, upconversion, downshifting, and thermal-stimulated luminescence simultaneously in a single nanoparticle under multichannel excitation and stimuli. These results provide new insights into the mechanism of X-ray induced mechanoluminescence in nanocrystals and contribute to the development of smart luminescent materials toward X-ray imaging encryption, stress sensing, and anticounterfeiting.

Light-responsive multimode luminescence in photochromism transparent wood for anti-counterfeiting application

With the rapid development of information technology, people’s security awareness of information protection is enhanced, and the requirements for anti-counterfeiting technology have become higher and higher on different occasions. Smart materials with light stimulus response have attracted extensive attention in the development of anti-counterfeiting materials, especially next-generation intelligent transparent wood. Inspired by the color-changing behavior of plants and animals in nature, a photochromic transparent wood (PTW) composite with light-stimulated response was prepared by compounding rare earth luminescent complexes with transparent wood (TW). PTW exhibits high transmittance (85.5 %). Moreover, PTW exhibits different optical states under different light conditions, namely, colorless under sunlight and bright red fluorescence under 365-nm UV light, and the process is reversible. Additionally, PTW patterned by laser etching offered greater flexibility and personalization in terms of stimulus-response, and its information security under different light stimuli is demonstrated. Meanwhile, the PTW prepared can be applied to different products and their packaging as an invisible anti-counterfeiting label, and the storage and protection of information is realized under visible light, and the decoding of information is implemented in UV light, so as to achieve the invisible anti-counterfeiting of information. More importantly, invisible information can be clearly identified even in black packaging. The design concepts and techniques of this study provide an inspiration to combine smart responsive materials with wood-based materials to develop intelligent responsive materials, and also provides support for the subsequent design and preparation of invisible anti-counterfeiting materials.

Multi-Mode Luminescence in Smart Near-Infrared Cr3+/Pr3+ Codoped SrGa12O19 Phosphors Induced by Three Distinct Excitation Mechanisms.

Near-infrared (NIR) phosphors have emerged as novel luminescent materials across various fields due to their unique advantages of high penetration and invisibility. However, there is currently a lack of intelligent NIR phosphors that can achieve multimode stimuli responsive for sensing applications. In this study, we employed a high-temperature solid-phase reaction to incorporate Pr3+ into Cr3+-doped gallate magnetite SrGa12O19 phosphor, yielding a multimode luminescent intelligent NIR phosphor. Also, due to the inherent cation vacancies and defects in the matrix, the material not only exhibits brighter photoluminescence but also exhibits distinct NIR mechanoluminescence at a lower load. Notably, Pr3+-doped SrGa12O19:Cr3+ also demonstrates extended persistent luminescence and thermoluminescence effects. Finally, we combined the phosphor with the blue LED chip to develop a new multifunctional NIR pc-LED. Leveraging NIR's unique penetrating ability, it can persist in biological tissues for prolonged periods, enabling optical inspection and offering a novel approach to password protection for anticounterfeiting measures. This intelligent NIR phosphor solution significantly expands the application potential of NIR light in food quality assessment and analysis.

Multi-color and multi-mode luminescence tuning in persistent phosphors by trap engineering

Conventional persistent luminescent phosphors face a significant challenge in developing a single material for multi-color anti-counterfeiting. In this study, a wide range of Cr3+ activated gallium germanate-based persistent phosphors are successfully synthesized using high-temperature solid phase approach. By incorporating Cr3+ and Er3+ as dual emitting centers, and utilizing Yb3+ as a sensitizer and electron traps, the resulting phosphors exhibit an exceptional combination of photoluminescence, up-conversion luminescence, persistent luminescence, photo/thermo-stimulated luminescence, followed by photo-stimulated persistent luminescence in a single material system. Beyond its multi-mode emissions, the luminescence color output can be conveniently controlled by adjusting annealing time, Yb3+ ion doping concentration, excitation wavelength, or excitation power. A systematic study of trap distribution related to PersL has been conducted by regulating annealing temperature, time, doping concentration and type. The responding multi-mode luminescent mechanisms are also proposed. Particularly, these phosphors demonstrated outstanding performance as security labels in advanced anti-counterfeiting applications. This research holds the potential to inspire the design and development of more intricate luminescence anti-counterfeiting materials and technologies.

Eu2+-Eu3+ Co-doping provoking polyhedron-cluster-based emission structural unit evolution triggering phases transition and blue-green-red multimode luminescence emission

A series of Ca2-xSiO4:xEu2+/Eu3+ and Ca2-2xSiO4:xEu2+/Eu3+, xM (M = Na+, K+) phosphors were prepared by co-doping Eu2+-Eu3+ in Ca2SiO4 solid solution for selectively locating Eu2+-Eu3+ ions deriving polyhedron-distorted emitting structure units’ evolution. During β, γ1,2-C2S matrix phase transitions, the structure and luminescence properties were analyzed by XRD, diffuse reflection, PL and luminescence thermal stability. The results show that Eu2+/Eu3+ occupying 6 Ca2+ sites forms 10 emission structural units in the matrix and the phase transition of γ1-Ca2-xSiO4(x = 0.0001–0.0004)→β-Ca2-xSiO4 (x = 0.0005–0.04)→β, γ2-Ca2-xSiO4 mixed phase (x = 0.08–0.32) is generated by the extrusion of structural units. Ultraviolet–visible diffuse reflectance spectra confirm the band gap difference caused by structural unit rotation. According to the bond energy method, the priority occupation order for the Eu2+/3+ ions was determined. The energy transfer of Eu2+→Eu3+ occurs when the structural units 3–10 of β, γ2-Ca2-xSiO4 mixtures coexist. After co-doped M+ as charge compensator, the luminescence intensity/thermal stability of Ca2-2xSiO4:xEu3+, xM(M = Na+, K+) were improved by 33.88 %/57.12 %, and 5.1 %/6.6 % than that of Ca2-xSiO4:xEu3+, respectively. These characteristics indicate that phosphors have broad application prospects in the field of solid-state lighting.

Multimode Luminescence with Temperature and Energy Level Synergistic Dependence in Rare Earth Halide DPs for Advanced Multifunctional Applications.

Rare-earth halide double perovskites (DPs) have attracted extensive attention due to their excellent optoelectronic performance. However, the correlation between luminescence performance, crystal structure, and temperature, as well as the inherent energy transfer mechanism, is not well understood. Herein, Lanthanide ions (Ln3+: Nd3+ or Dy3+) as the co-dopants are incorporated into Sb3+ doped Cs2NaYbCl6 DPs to construct energy transfer (ET) models to reveal the effects of temperature and energy levels of rare earth on luminescence and ET. The different excited state structures of Sb3+-Ln3+ doped Cs2NaYbCl6 DPs at different temperatures and relative positions of energy levels of rare earth synergistically determine the physical processes of luminescence. These multi-mode luminescent materials exhibit good performance in anti-counterfeiting, NIR imaging, and temperature sensing. This work provides new physical insights into the effects of temperature and energy levels of rare earth on the energy transfer mechanism and related photophysical process.

Ultraviolet-B and Near-Infrared Dual-Band Luminescence in Bi3+/Bi2+ Codoped Persistent Phosphor for Optical Storage Application.

Discovering multifunctional luminescent materials to meet the demands of modern spectroscopy is of great significance. However, it is a standing challenge to enable multiple luminescence properties in a single material system via single metal ion doping. Here, we report the inherently Bi3+/Bi2+ codoped Ca3Ga2Ge3O12 persistent phosphor where Bi3+ is in situ reduced to Bi2+. This phosphor can act as an efficient multimodal luminescence material, which simultaneously exhibits long-lasting (>12 h) ultraviolet-B (UVB) and near-infrared (NIR) dual-band persistent luminescence after irradiation by 254 nm ultraviolet (UV) light. UVB and NIR afterglow are ascribed to the distinct Bi3+ and Bi2+ emitters, respectively, proven by comprehensive spectroscopic investigations including X-ray absorption near-edge structure spectra and X-ray photoelectron spectroscopy. Besides, this phosphor also exhibits exceptional photochromic features, accompanied by a rapid body color transformation from white to brown in response to 254 nm UV light within 60 s and excellent recovery capacity upon thermal or blue/white light stimulation. The combination of UVB persistent luminescence of Bi3+ and NIR afterglow of Bi2+ coupled with reversible white-to-brown photochromism phenomenon offers one type of promising multifunctional luminescence material, showing potential to be used for optical storage and anti-counterfeiting applications.