Abnormal thermal quenching behavior and optical properties of a novel apatite-type NaCa3Bi(PO4)3F:Sm3+ orange-red-emitting phosphor for w-LED applications

Novel apatite-type NaCa₃Bi(PO₄)₃F:xSm³⁺ (0.01 ≤ x ≤ 0.30) orange-red-light phosphors were synthesized through the solid-state method at high temperature. The crystal structure, energy band structure, density of state, phase purity, particle morphology, photoluminescence properties, thermostability, and luminescence decay of the phosphors were comprehensively characterized. When λ_ex = 404 nm, the optimal NaCa₃Bi(PO₄)₃F:0.05 S m³⁺ phosphor showed the orange-red emission (597 nm). The NaCa₃Bi(PO₄)₃F:Sm³⁺ phosphors exhibited abnormal thermal quenching properties as their emission intensity increased by about 2.57% from 300 to 380 K. Their intensity at 440 K was still 1.01-fold stronger than that at room temperature. The abnormal thermal quenching mechanisms were well explained via the coordinate configuration scheme. The thermal activation energy (E_a) was calculated to be 0.79 eV. The color purity of all the phosphors reached 99.9%. Ultimately, a white light-emitting diode (w-LED) was fabricated based on the tri-color RGB method. The color rendering index and the chromaticity coordinates of the fabricated w-LED were 89 and (0.310, 0.319), respectively. Thus, these high thermostability NaCa₃Bi(PO₄)₃F:Sm³⁺ orange-red phosphors can be potentially used in w-LED applications.     

Improvement the near-infrared luminescence properties of double perovskite phosphor La(Mg0.5Sn0.5In0.5Sc0.5)0.5O3:Cr3+ via co-doping Yb3+

In recent years, the broadband near-infrared (NIR) spectroscopy technology has been widely used in the field of nondestructive testing. However, these existing NIR phosphors showed relatively short emission wavelengths, narrower half-maximum full-width (FWHM), and narrower half-peak widths, importantly, few phosphors presented the emission from 950 nm to 1100 nm. In order to solve these problems, the Yb³⁺/Cr³⁺ ions codoped La(Mg_0.5Sn_0.5In_0.5Sc_0.5)_0.5O₃ (LMSIS) was synthesized by the solid-state method, and the emission spectrum of LMSIS:Cr³⁺ can be extended to the NIR long-wave region due to the energy transfer of Yb³⁺ and Cr³⁺, and the thermal stability of the phosphor can be improved due to the inherent temperature stability of the Yb³⁺ f-f transition. The NIR phosphor converted light emitting diodes (pc-LEDs) were fabricated by combining the LMSIS:0.003Cr³⁺, 0.0015Yb³⁺ with blue LED chip, which can be expected to be used in the field of broadband near-infrared non-destructive detection.     

Luminescence and optical thermometry based on silico-carnotite Ca3Y2Si3O12: Pr3+ phosphor

The photoluminescence and temperature sensitivities of Ca₃Y₂Si₃O₁₂:Pr³⁺ thermo-phosphors with silico-carnotite structure obtained by solid state reaction method were investigated. Pr³⁺ ions were accommodated in the A sites having coordination number of 9 in AB₂C₂(SiO₄)₃ to replace Y³⁺ ions. The typical sample consisted of microcrystals with an irregular structure and the surface of particles was smooth, which could enhance the luminescence due to reducing the scattering and non-radiation produced by rough surfaces. The band gap value of typical sample was about 4.01 eV. Dipole-dipole interaction could account for concentration quenching. The two thermometry strategies including normalized intensities from ³P₀→³H₄ transition and Fluorescence intensity ration (FIR) of ³P₀→³H₄/³P₁→³H₅ transitions were employed for temperature sensing in 298–573 K. The results revealed that Ca₃Y₂Si₃O₁₂:Pr³⁺ thermo-phosphors had good temperature sensitivity performance with maximum S_r of 0.59% K^?1@573 K and 0.762% K^?1@298 K in the above two methods, respectively. Hence, Ca₃Y₂Si₃O₁₂:Pr³⁺ would be a promising candidate in the field of optical thermometry.     

Thermal enhancement of up-conversion luminescence in Lu2W2.5Mo0.5O12: Er3+, Yb3+ phosphors

Lu₂W_2.5Mo_0.5O₁₂: Er³⁺/Yb³⁺ phosphors were synthesized through high temperature solid state method. Under 980 nm laser excitation, the Lu₂W_2.5Mo_0.5O₁₂: Er³⁺/Yb³⁺ compounds show thermal enhancement of up-conversion luminescence (UCL), which is attributed to the lattice contraction and distortion from negative thermal expansion (NTE) of Lu₂W_2.5Mo_0.5O₁₂ host enhancing the energy transfer of Yb³⁺ to Er³⁺, eliminating the energy transfer of Er³⁺ to Er³⁺ through Er³⁺ single-doped Lu₂W_2.5Mo_0.5O₁₂ phosphors without thermal enhancement of UCL. The green luminescence intensities at 693 K of the Lu_1.98-xW_2.5Mo_0.5O₁₂: 0.02Er³⁺, xYb³⁺ (x = 0.2, 0.3, 0.4) samples are 4.6, 4.3 and 7.0 times as that of 302 K, respectively. And through fluorescence intensity ratio (FIR) technique, the corresponding maximum absolute sensitivities are 0.00741, 0.00744 and 0.00723, respectively. The green monochromaticity of UCL spectra in Er³⁺/Yb³⁺ co-doped samples increase with the increasing of temperature, and the possible UCL mechanism with temperature was discussed. The results indicate that the Lu₂W_2.5Mo_0.5O₁₂: Er³⁺/Yb³⁺ phosphors can be applied at a high temperature as optical thermometer with a good green monochromaticity.     

Luminescence and self-referenced optical temperature sensing performance in Ca2YZr2Al3O12:Bi3+,Eu3+ phosphors

Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ phosphors were elaborated by a traditional solid-state reaction method. The luminescence of Ca₂YZr₂Al₃O₁₂:Bi³⁺ samples, energy transfer from Bi³⁺ to Eu³⁺, and the temperature sensing properties of Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ samples have been systematically researched. Under the excitation of ultraviolet light, Bi³⁺ single doped phosphors give 313 and 392 nm emission bands, which origin from the substitutions of Bi³⁺ instead of Ca²⁺ and Y³⁺ sites, respectively. And the color-adjustable emission from blue to red were observed by increasing Eu³⁺ content in Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ samples. Relying on different temperature dependent variation tendency, the fluorescence intensity ratio (FIR) values present outstanding temperature sensing properties. The absolute and relative sensitivity can be up to 0.826 %K^-1 and 0.664 %K^-1, respectively. All above results suggest that Ca₂YZr₂Al₃O₁₂:Bi³⁺,Eu³⁺ phosphor is a potential alternative for optical thermometer.     

Synthesis and luminescence enhancement of red-emitting Sr9Y(PO4)7:Eu3+ phosphor through Gd3+ co-doping for white light-emitting diodes

A series of Sr₉Y(PO₄)₇:Eu³⁺ and Sr₉Y(PO₄)₇:Eu³⁺, Gd³⁺ red-emitting phosphors were prepared via a high-temperature solid-state method, Gd³⁺ ion was co-doped in Sr₉Y(PO₄)₇:Eu³⁺ as sensitizer to enhance the luminescence property. The X-ray diffraction results verify that the structure of the as-prepared samples is consistent with the standard Sr₉Y(PO₄)₇ phase. All the Sr₉Y(PO₄)₇:Eu³⁺ samples show both characteristic emission peaks at 594 nm and 614 nm under near-ultraviolet excitation of 394 nm. The co-doping of Gd³⁺ significantly improves the luminescence intensity of the Sr₉Y(PO₄)₇:Eu³⁺ phosphors due to the crystal field environment effect and energy transfer of Gd³⁺→Eu³⁺ caused by the introduction of Gd³⁺, especially Sr₉Y(PO₄)₇:0.11Eu³⁺, 0.05Gd³⁺, which emission intensity is higher than that of Sr₉Y(PO₄)₇:0.11Eu³⁺ by 1.21 times. The color purity and lifetime of Sr₉Y(PO₄)₇:0.11Eu³⁺, 0.05Gd³⁺ phosphor are 88.26% and 3.7615 ms, respectively. A w-LED device was packaged via coating the as-prepared phosphor on n-UV chip of 395 nm with commercial phosphors. These results exhibit that the Sr₉Y(PO₄)₇:Eu³⁺, Gd³⁺ red-emitting phosphor can be used as a red component in the w-LEDs application.     

Improving the luminescence and afterglow properties of Mg3Y2Ge3O12:Cr3+ by co-doping Bi3+

Generally, the emission intensity and afterglow of the near infrared phosphors can be improved by co-doping the sensitizer. In this work, Bi³⁺ ions as sensitizer are introduced into the near infrared phosphor Mg₃Y₂Ge₃O₁₂:Cr³⁺, and the luminescence properties are investigated. According to the principle of radius adaptation, Bi³⁺ ions would occupy eight coordinates in the host instead of Y³⁺ and Mg²⁺. Through structural refinement, theoretical calculation and experimental phenomena, there are two kinds of luminescent sources for Bi³⁺ ions, which come from ³P₁ → ¹S₀ (441 nm) and MMCT (330 nm), respectively. In addition, the substitution of Bi³⁺ for Mg²⁺ will result in inequivalent substitution forming defects (Bi_Mg·), and the trap depth is 0.55 eV. For Bi³⁺ and Cr³⁺ co-doped Mg₃Y₂Ge₃O₁₂, there are two factors can that can affect the luminescent properties of Cr, which are energy transfer and defects. The samples are obtained with three times the original emission intensity with the introduction of defects. At the same time, Bi³⁺ ions capture electrons to form new electron traps Bi²⁺ (Bi³⁺ + e^-) and the trap depth is 0.81 eV. Therefore, under the action of two traps Bi_Mg· and Bi²⁺ (Bi³⁺ + e^-), the afterglow characteristics of the samples are improved and the time can reach 1.5 h.     

Sr3GdLi(PO4)3F:Eu2+, Mn2+: A tunable blue-white color emitting phosphor via energy transfer for near-UV white LEDs

A series of Eu²⁺ and Mn²⁺ co-doping Sr₃GdLi(PO₄)₃F phosphors have been synthesized through high temperature solid state reaction. Eu²⁺ single doped Sr₃GdLi(PO₄)₃F phosphors have an efficient excitation in the range of 230–430 nm, which is in good agreement with the commercial near-ultraviolet (n-UV) LED chips, and gives intense blue emission centering at 445 nm. The critical distance of the Eu²⁺ ions in Sr₃GdLi(PO₄)₃F is computed and demonstrated that the concentration quenching mechanism of Eu²⁺ is mostly caused by the dipole-dipole interaction. By co-doping Eu²⁺ and Mn²⁺ ions in the Sr₃GdLi(PO₄)₃F host, the energy transfer from Eu²⁺ to Mn²⁺ that can be discovered. With the increase of Mn²⁺ content, emission color can be adjusted from blue to white under excitation of 380 nm, corresponding to chromatic coordinates change from (0.189, 0.108) to (0.319, 0.277). The energy transfer from Eu²⁺ to Mn²⁺ ions is proven to be a dipole-dipole mechanism on the basis of the experimental results and analysis of photoluminescence spectra and decay curves. This study infers that the obtained Sr₃GdLi(PO₄)₃F:Eu²⁺, Mn²⁺ phosphors may be a potential candidate for n-UV LEDs.     

Luminescence properties and energy transfer of GdAl3(BO3)4:Ce3+, Tb3+ phosphor

Ce³⁺ and Tb³⁺ singly doped and co-doped GdAl₃(BO₃)₄ phosphors were synthesized by solid state reaction. The crystal structure, the luminescent properties, the lifetimes and the temperature-dependent luminescence characteristic of the phosphors were investigated. Through an effective energy transfer, the emission spectra of GdAl₃(BO₃)₄:Ce³⁺, Tb³⁺ phosphor contains both a broad band in the range of 330–400 nm originated from Ce³⁺ ions and a series of sharp peaks at 484, 541, 583, and 623 nm due to Tb³⁺ ions. The energy transfer from Ce³⁺ to Tb³⁺ in GdAl₃(BO₃)₄ host is demonstrated to be phonon assisted nonradiative energy transfer via a dipole–dipole interaction.     

A novel pure red phosphor Ca8MgLu(PO4)7:Eu3+ for near ultraviolet white light-emitting diodes

A novel red-emitting phosphor Ca₈MgLu(PO₄)₇:Eu³⁺ was synthesized by a high-temperature solid-state reaction method. Its crystal structure, photoluminescence emission and excitation spectra, and decay time were investigated in detail. X-ray diffraction (XRD) results indicate that Ca₈MgLu(PO₄)₇ crystallizes in single-phase component with a whitlockite-like structure and the space group R3c of β-Ca₃(PO₄)₂. The emission spectrum shows a dominant peak at 612 nm due to the dipole ⁵D₀→⁷F₂ transition of Eu³⁺, and the luminescence intensity keeps increasing with increasing the content of Eu³⁺ to 100%. The excitation spectrum is coupled well with the emission of near ultraviolet (NUV) LED (380–410 nm). The CIE coordinates of Ca₈MgLu(PO₄)₇:Eu³⁺ phosphor is (0.654, 0.346), being close to the standard value of National Television Standard Committee (NTSC) for red phosphor, (0.670, 0.330). The internal quantum efficiency of the phosphor is 69% under the excitation of 394 nm. The results show that Ca₈MgLu(PO₄)₇:Eu³⁺ is a very appropriate red-emitting phosphor with a high ratio of red and orange for NUV-based white LEDs.     

Fluorescence properties with red-shift of Eu2+ emission in novel phosphor-silicate apatite Sr3LaNa(PO4)2SiO4 phosphors

A series of Eu²⁺-activated novel phosphor-silicate apatite Sr₃LaNa(PO₄)₂SiO₄ phosphors were synthesized by solid-state reaction. The X-ray diffraction (XRD) and Rietveld refinement, diffuse reflectance spectra, luminescent spectra, decay curves and thermal quenching properties were applied to characterize the obtained phosphors. The XRD result revealed that all the samples possessed only a single phase with hexagonal structure and the doping of Eu²⁺ ions were successfully incorporated into the crystal lattice. The reflectance spectra showed an obvious red-shift of the wavelength from 400 to 700 nm with increasing Eu²⁺ ion concentration. The three different crystallographic sites of Eu²⁺ ions had been confirmed by their lifetimes. All the samples exhibited broad absorption bands from 200 to 450 nm, revealing the phosphor-silicate phosphor interesting for application in the near-UV used phosphor-converted LED chips. These results suggested that the Eu²⁺-activated phosphor-silicate Sr₃LaNa(PO₄)₂SiO₄ phosphors have the potential for near-UV pumped white-light-emitting diodes (w-LEDs).     

Preparation,crystal structure and luminescence properties of red-emitting Lu3Al5O12: Mn4+ ceramic phosphor

A series of red-emitting Mn⁴⁺ doped Lu₃Al₅O₁₂ (LuAG) ceramic phosphors were successfully prepared by a simple solid-state reaction method in a high-temperature muffle. MgO was co-doped as sintering aids and Mg²⁺ ions helped to realize the charge balance. The relations between the luminescence properties, crystal structures and the microstructures were well established. Results indicated that MgO promoted the densification of the ceramics as the specimens’ relative densities were up to 99%. Moreover, the substitution of Al³⁺ with Mg²⁺ have changed crystal structures and further affected the luminescent properties. Overall, the obtained ceramic phosphors showed strong red-light emission under excitation of ultraviolet and blue light. By optimizing the Mg²⁺ and Mn⁴⁺ concentration, a quantum efficiency (QE) as high as 47.8% can be achieved under the excitation of 460 nm light, indicating that the LuAG: Mn⁴⁺ ceramic phosphors are promising candidates for WLEDs applications.     

Tunable luminescence and energy transfer properties of MgY4Si3O13: Ce3+, Tb3+, Eu3+ phosphors

The tricolor-emitting MgY₄Si₃O₁₃: Ce³⁺, Tb³⁺, Eu³⁺ phosphors for ultraviolet-LED have been prepared via a high-temperature solid-state method. X-ray diffraction, photoluminescence emission, excitation spectra and fluorescence lifetime were utilized to characterize the structure and the properties of synthesized samples. Two different lattice sites for Ce³⁺ are occupied from the host structure and the normalized PL and PLE spectra. The emissions of single-doped Ce³⁺/Tb³⁺/Eu³⁺ are located in blue, green and red region, respectively. The energy transfer from Ce³⁺ to Tb³⁺ and from Tb³⁺ to Eu³⁺ has been validated by spectra and decay curves and the energy transfer mode from Tb³⁺ to Eu³⁺ was calculated to be electric dipole-dipole interactions. By adjusting the content of Tb³⁺ and Eu³⁺ in MgY₄Si₃O₁₃: Ce³⁺, Tb³⁺, Eu³⁺, the CIE coordinates can be changed from blue to green and eventually generate white light under UV excitation. All the results indicate that the MgY₄Si₃O₁₃: Ce³⁺, Tb³⁺, Eu³⁺ phosphors are potential candidates in the application of UV-WLEDs.     

Synthesis,structure and luminescence properties of a novel red fluorescent material Ba2MgB2O6:Eu3+

The crystal structure of Ba_2-xMgB₂O₆:xEu³⁺ phosphors, synthesized using a solid-state reaction, have been confirmed by X-ray diffraction analysis. This study focuses on the site occupancy preference of Eu³⁺ ions within the matrix, which was determined using bond energy theory, fluorescent spectra, and a consideration of energy transport and decay curves. The impact of Eu³⁺ ion concentration on luminescence has been assessed, and an optimal concentration (x = 0.22) identified. The critical distance, R_c was 9.6 Å, with a calculated θ value of 19.67, indicating that quadrupole-quadrupole interaction plays a critical role in the quenching Ba_2-xMgB₂O₆:xEu³⁺ phosphors. The Ba_2-xMgB₂O₆:xEu³⁺ phosphors exhibited a color purity of 99.26%, and a quantum efficiency of 49.68%. The activation energy Ea was determined to equal 0.2987 eV. The results have established Ba_1.78MgB₂O₆:0.22Eu³⁺ as a red fluorescent powder with high quantum efficiency and a millisecond fluorescence lifetime.     

Effect of Y3+-O2- partial substitution with Ca2+-F- on the luminescence enhancement of Y2Mo3O12:Sm3+ red-emitting phosphors

To improve the luminescence property of Sm³⁺ in Y₂Mo₃O₁₂, partial Ca²⁺-F^- co-substituted Y₂Mo₃O₁₂:Sm³⁺ phosphor, namely Y_2-xCa_xMo₃O_12-xF_x:Sm³⁺, was prepared using a solid-state method. The effect of introducing Ca²⁺-F^- ion pairs on structure and luminescence properties of Y₂Mo₃O₁₂:Sm³⁺ was studied in depth. XRD patterns not only manifested that all as-prepared Y_2-xCa_xMo₃O_12-xF_x:Sm³⁺ samples had standard Y₂Mo₃O₁₂ structure, but also indicated the introduction of Ca²⁺-F^- ion pairs did not cause the change of crystal structure. Under the near ultraviolet excitation of 404 nm, the emission peaks of Y₂Mo₃O₁₂:Sm³⁺ were located at 567 nm, 605 nm and 652 nm, respectively, resulting from the 4f→4f electron transitions of Sm³⁺ ions. Furthermore, the luminescence intensity of Sm³⁺ was obviously enhanced through the co-substitution of Y³⁺-O^2- ions with Ca²⁺-F^- ions in Y₂Mo₃O₁₂ structure, and the chromaticity coordinates moved towards red region, which due to the environmental effect of crystal field around Sm³⁺. Besides, the red LED device was manufactured for suitable chromaticity parameters. All results indicated that the as-prepared Y_1.84Ca_0.06Mo₃O_11.94F_0.06:0.10Sm³⁺ red-emitting phosphor could become a promising candidate for application of white light-emitting diodes and plant illumination.     

Structure evolution and delayed quenching of the double perovskite NaLaMgWO6:Eu3+ phosphor for white LEDs

Eu³⁺ ions activated NaLaMgWO₆ phosphors were successfully synthesized by an improved sol-gel method using citric acid and polyethylene glycol as complexing agents. Crystal structure and doping site were investigated by XRD, Rietveld refinement and Raman spectra. The phosphors had monoclinic double perovskite structure with space group C2/m, as well as layered ordering of A-site and rock-salt ordering of B-site. The blueshift of Raman T_2g(1) mode manifested Eu³⁺ ions had entered into A-site. Thereafter, luminescence properties, such as excitation and emission spectra, CIE coordinates, concentration quenching and thermal quenching were discussed. The quenching concentration for hypersensitive electric dipole transition of Eu³⁺ reached up to 50.0 mol%. The delayed concentration quenching was observed in NaLaMgWO₆: Eu³⁺ phosphor. The theoretical quenching concentration was obtained based on L. Ozawa's theory, and the quenching mechanism on Dexter's theory. Excellent thermal stability of this phosphor shows that it is a potential red phosphor for solid state lighting.     

LiCa3MgV3O12:Sm3+: A new high-efficiency white-emitting phosphor

A novel single-phased white-light-emitting phosphor Sm³⁺ doped LiCa₃MgV₃O₁₂ (LCMV) was developed. The LCMV host was one self-activated bluish-green emitting phosphor, which possessed an efficient excitation band in the 250–400?nm wavelength range and showed an intense broadband bluish-green emission with internal quantum efficiency (IQE) of 39%. Doping Sm³⁺ ions in to LCMV host induced tunable-color emissions, due to the energy transfer from [VO₄]^3? to Sm³⁺ ions. Importantly, under 340?nm excitation, the LCMV:Sm³⁺ can emitted bright white light by combining the self-activated luminescence of LCMV host and the red emissions of Sm³⁺ ions, and the IQE of the white-emitting composition-optimized LCMV:0.01Sm³⁺ phosphors reached up to 45%. These white-emitting LCMV:Sm³⁺ phosphors have potential applications in white light-emitting diodes and optical display devices.     

Luminescence properties of a novel greenish-blue emission long persistent phosphor Sr3TaAl3Si2O14:Pr3+

Pr³⁺exhibits prominent red emission in most oxide phosphors, which derives from the ¹D₂→³H₄ transition, and green or blue emission from ³P₀→³H_{4, 5} transitions are normally less intense in most cases. However, a greenish-blue emission was observed from Sr₃TaAl₃Si₂O₁₄:Pr³⁺prepared via solid state reaction. All as-prepared phosphors were studied systematically by X-ray diffraction (XRD), photoluminescence spectra, decay curves, long afterglow (LAG) spectra and thermoluminescence (TL) glow curves. Based on the excitation and emission spectra, the Sr₃TaAl₃Si₂O₁₄ (STAS) host is proved to be a self-activated luminescent host lattice. In the emission spectra for Pr³⁺doped STAS, the predominant greenish-blue emission locating at ~489 nm and ~507 nm coming from ³P_0,1→³H₄ transitions were observed. And the different mechanisms for concentration quenching in both cases were discussed. At last, a model was proposed on the basis of experimental results to discuss the LAG mechanism of STAS:Pr³⁺in detail.     

Structural and luminescence studies on thermally stable Bi3+-activated Ba3MoTiO8 phosphors for near UV-pumped w-LED applications

This research presents the outcomes of diverse morphological and photoluminescence (PL) studies performed on Bi³⁺ ion–doped Ba₃MoTiO₈ phosphors prepared via the conventional solid-state reaction method. Phase assessment was carried out via the X-ray diffraction (XRD) studies. Field emission scanning microscopy (FE-SEM) and energy-dispersive X-ray analysis (EDAX) have been used to study the surface morphology anda elemental composition. Fourier transform infrared spectroscopy (FT-IR) was used to study the character and vibrational frequencies of bonds in the phosphor lattice. Room-temperature PL was performed under 275 and 386 nm excitations, displaying a broad band in the blue region corresponding to the ³P₁ → ¹S₀ transition of Bi³⁺ ions. The Commission Internationale de L'Eclairage coordinates and correlated color temperature values show that the as-prepared phosphors emit in the blue vicinity. The decay curves under both excitation wavelengths show a single exponential behavior. Temperature-dependent PL studies confirmed the high thermal stability of the phosphor. We want to endorse these phosphors as a blue-emitting component in white light-emitting diodes (w-LEDs) and solid-state lighting (SSL) applications.     

Dual-mode dichromatic SrBi4Ti4O15: Er3+ emitting phosphor for anti-counterfeiting application

Fluorescent materials have been widely used for anti-counterfeiting of important documents and currencies, wherein their anti-counterfeit abilities could be improved through multi-mode excitation. Herein, dual-mode-excited double-colour-emitting Er³⁺doped SrBi₄Ti₄O₁₅ up-conversion (UC) phosphors (SBTO: Er³⁺) were synthesised, and their UC spectra included green (2H11/2/4S3/2 → 4I15/2) and red (4F9/2 → 4I15/2) emissions from Er3+ ions under 980 or 1550 nm excitation. However, the green emission colour of phosphors was independent of dopant concentration under 980 nm laser irradiation; whereas the final emission colour was dominated by red emission and significantly affected by contents of Er3+ under 1550 nm excitation. These observations demonstrated potential application in dual-mode double-colour anti-counterfeiting. The possible UC mechanisms and emission characteristics of the phosphors using different 980 and 1550 nm irradiation source were contrastively investigated, and some fluorescent security patterns were also designed to demonstrate the potential applications in anti-counterfeiting and concealing important information.