High-efficiency Mn²⁺-rich phosphors toward wide color gamut LCDs and advanced X-ray imaging applications

Heng Dai, Xinran Wang, Zhichao Liu, Junli Liu, Xiuxia Yang* and Jie Yu*
Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming Yunnan 650093, P. R. China. E-mail: xiuxia941129@163.com; yujie@kust.edu.cn

First published on 6th August 2025

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1. Introduction

The development of display technology and medical imaging has promoted the continuous progress of science and technology.^1–5 As an important component of modern display technology, liquid crystal display (LCD) backlight technology is widely applied in TVs, mobile phones, computers, etc., and its performance directly determines the display effect and user experience.^6–8 Similarly, X-ray imaging technology plays an indispensable role in medical diagnosis, industrial testing, and other fields.^9–11 However, the spatial incompatibility between traditional rigid X-ray flat panel detectors and three-dimensional (3D) objects significantly affects the resolution and integrity of imaging patterns. To overcome this limitation, the development of flexible X-ray detectors with improved imaging performance has become a promising trend for the future.^12–15 Meanwhile, achieving higher performance requires careful selection and optimization of materials. Traditional optical materials struggle to meet the increasing demands of practical applications, while multifunctional optical materials have emerged as a critical solution due to their excellent performance, efficiency, adaptability, and broad application scope.^16–19 Until now, the research on multifunctional optical materials has been limited, especially in the systematic research of material synthesis, performance optimization and application development.^20,21 Exploring new multifunctional optical materials is expected to not only promote the development of cutting-edge optoelectronic technologies but also to provide sustainable solutions to urgent environmental challenges.

Mn²⁺, a commonly used transition metal ion, exhibits diverse optical properties due to its 3d⁵ electrons, which are sensitive to the crystal field.^22,23 In a weak tetrahedral field, Mn²⁺ typically emits green light with a full width at half maximum (FWHM) ranging from 26 to 43 nm. For instance, γ-AlON (FWHM = 43 nm),²⁴ MgAl₂O₄ (FWHM = 35 nm),²⁵ and Sr₂MgAl₂₂O₃₆:Mn²⁺ (FWHM = 26 nm)²⁶ are green phosphors that cover a wide National Television System Council (NTSC) color gamut (>110%) and therefore are suitable for LCD backlight displays. However, the photoluminescence quantum yield (PLQY) of Mn²⁺-activated phosphors is low because of the parity-forbidden transition, limiting their practical applications.^27–29 A common approach to improving PLQY is to increase the doping concentration of Mn²⁺, thereby enhancing the density of activators. However, high doping concentrations often lead to severe aggregation of Mn²⁺ ions, reducing emission efficiency.^30–32 To mitigate this issue, the structural confinement effect can effectively suppress the concentration quenching by controlling the distance between the luminescent centers, and introduce as many emission centers as possible in the host.^33,34 This simple and effective strategy requires the matrix material to meet specific structural requirements to ensure that it can effectively accommodate activator ions and avoid concentration quenching effects.

Hexagonal aluminate-based luminescent materials represent a class of compounds with unique layered structures and excellent physical and chemical stability. In recent reports, Mn²⁺-doped BaMgAl₁₀O₁₇ (BAM) narrow-band green phosphors have shown great potential in LCD applications. However, the lack of luminous efficiency and thermal stability limits their practical application.^35,36 In this study, we selected a nonstoichiometric BaMg_1.072Al_9.928O₁₇ crystal as the matrix, featuring a slightly distorted β-Al₂O₃ structure. The isolated Mg²⁺ sites, located within densely packed spinel blocks, possess a highly rigid structure. This arrangement results in a narrow full width at half maximum (FWHM = 26 nm) and low thermal quenching (90%@423 K) for doped Mn²⁺ ions. Notably, the distance between isolated Mg²⁺ sites (10.27 Å) effectively suppresses concentration quenching of Mn²⁺ emission centers. The PLQY of the BMAO:0.6Mn²⁺ phosphor reaches 94.9%, demonstrating remarkable efficiency. When incorporated into a light-emitting diode (WLED), the fabricated device achieves an NTSC coverage of 125.3%, demonstrating significant potential for LCD applications. Furthermore, a flexible film prepared using BMAO:0.6Mn²⁺ and polydimethylsiloxane (PDMS) exhibits a minimum detection limit of 35.8 nGy s⁻¹ and a spatial resolution of 18.0 lp mm⁻¹, highlighting its utility in X-ray 3D imaging. Our work thus provides a promising dual-function material for both high-performance LCD displays and advanced X-ray imaging technologies.

2. Results and discussion

2.1. Crystal structure and morphology analyses

The crystal structure of BMAO, as shown in Fig. S1 (SI), resembles that of other β-Al₂O₃ compounds. It consists of an ordered layered structure containing [BaO₆] triangular prisms, [Al1O₆] octahedra, [Mg/Al2O₄] tetrahedra, [Al3O₆] octahedra, and [Al4O₄] tetrahedra. The [Mg/Al2O₄] unit connects with the [Al1O₆] octahedron through shared angles along the axis, while the adjacent [Al3O₆] and [Al1O₆] octahedra are linked via shared edges. In the hexaaluminate structure, Mn²⁺ prefers to occupy the tetrahedron because of its lowest formation energy.²² Based on the principle of similar ionic radius and valence state, Mn²⁺ (r = 0.66 Å) is expected to occupy the sites of Mg²⁺ (r = 0.60 Å) rather than Al³⁺ (r = 0.39 Å) in the tetrahedron. In the spinel structure, the nearest distance of the Mg site in the [Mg/Al2O₄] tetrahedron is 3.42 Å in a single unit. However, due to the separation effect of the mirror symmetry plane, the nearest distance of the Al(2) sites in the interlayer [Mg/Al2O₄] increases to 10.27 Å. Based on this characteristic, a high Mn²⁺ doping concentration (x = 0.6) in the BMAO matrix is achieved.

Fig. S2 presents the X-ray powder diffraction (XRD) patterns of BMAO:xMn²⁺ (0 ≤ x ≤ 1.0) and the BMAO standard card (ICSD# 95998). The results demonstrate that all samples are in good agreement with the calculated values, with no obvious impurity phases observed. Fig. S3 and Fig. 1a display the Rietveld refinement results for BMAO and BMAO:0.6Mn²⁺, and the detailed results are listed in Table S1. The refinement results confirm that all samples belong to the typical hexagonal system, with lattice parameters, reliability factors, and atomic coordinates indicating that Mn²⁺ successfully occupies the Mg²⁺ site without affecting phase purity. To further verify the successful doping of Mn²⁺ and its valence state, X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) measurements were conducted on BMAO:0.6Mn²⁺. The XPS full spectrum (Fig. S4) shows the characteristic signals for all expected elements, such as Ba, Mg, Al, O, and Mn, in BMAO:0.6Mn²⁺. As shown in Fig. 1b, the binding energy peaks of 654.9 and 642.7 eV correspond to Mn 2p_3/2 and Mn 2p_1/2, respectively, indicating the presence of Mn²⁺ ions in the samples.³⁷ Additionally, the EPR spectrum of BMAO:0.6Mn²⁺ exhibits significant broadening, with a g-factor of 2.001 (Fig. 1c), attributed to strong magnetic dipole interactions between neighboring Mn²⁺ ions.³⁸ These findings strongly support the conclusion that the valence state of Mn is ‘+2’.

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are commonly used techniques to characterize the microscopic morphology of objects. Fig. S5a shows a representative SEM image of BMAO:0.6Mn²⁺, showing smooth and regular hexagonal particles with an average particle size of 3–5 μm. The elemental composition and atomic ratio are further analyzed by energy-dispersive X-ray spectroscopy (EDS). The EDS results agree well with the actual ratio (Fig. S5b). All elements are evenly distributed in the particles without aggregation or phase separation (Fig. 1d). Moreover, the high-resolution (HR) TEM image contains recognizable lattice fringes with a d-spacing of about 4.02 Å, corresponding to the (107) crystal plane of BMAO, as shown in Fig. 1e. Additionally, the (107) crystal plane is also observed in the regional electron diffraction of Fig. 1f. These results collectively demonstrate that the synthesized BMAO:Mn²⁺ possesses excellent crystallinity and uniform element distribution.

2.2. Optical properties of BMAO:Mn²⁺

Fig. 2a shows the UV-vis diffuse reflectance spectra (DRS) and PLE, PL spectra of BMAO:xMn²⁺ (x = 0, 0.2, 0.4, 0.6, 0.8). All samples show absorption in the UV–blue light region, which corresponds well with the peak positions of the PLE spectra. The peak at 260 nm is attributed to the charge transfer band (CTB) of Mn²⁺–O²⁻. Peaks at 355, 380, 430, and 455 nm correspond to the d–d transitions of Mn²⁺ from ⁶A₁ to ⁴E_g (⁴D), ⁴T_2g (⁴D), ⁴E_2g (⁴G) and ⁴T_2g (⁴G), respectively.^39,40 To better match the blue chip, 455 nm has been chosen as the excitation wavelength, and the highest emission peak is located at 523 nm. Fig. S6a shows the PLE and PL spectra of BMAO:xMn²⁺ (0.1 ≤ x ≤ 1.0). Under 455 nm excitation, the maximum emission peak of all samples is approximately 523 nm, with a full width at half maximum (FWHM) of 26 nm. The PL intensity of the BMAO:xMn²⁺ (0.1 ≤ x ≤ 1.0) samples increases initially and then decreases with increasing Mn²⁺ concentration. The position and FWHM value of the PL spectra remain nearly constant (Fig. 2b). Fig. S6a also shows a digital photo of the BMAO:0.6Mn²⁺ under 365 nm UV light irradiation. Interestingly, although Mn²⁺ occupies a single emission center, the spectrum is not completely symmetrical. This phenomenon arises from the electron–phonon interaction, the coordination environment of the activator ion, and the number of emission centers. Specifically, asymmetric coordination environments frequently lead to structural relaxation, which in turn results in broader emission bandwidth and spectral tailing.^41–43 Fig. S6b shows the decay curves of BMAO:xMn²⁺ (0.1 ≤ x ≤ 1.0) under 523 nm emission and 455 nm excitation. The calculated average lifetimes are 6.17, 6.07, 5.86, 5.35, 4.51, and 2.85 ms, corresponding to x values from 0.1 to 1.0. For highly Mn²⁺-doped phosphors, the shortened distance between Mn²⁺ ions causes a gradual decrease in the average lifetime. The millisecond lifetime of samples belongs to the optical characteristic of the Mn²⁺ ion, while the single-exponential decay (eqn (S1)) indicates the presence of a single emission center.⁴⁴ To confirm the existence of a single emission center, we recorded normalized the PLE and PL spectra of BMAO:0.6Mn²⁺ at various excitation and emission wavelengths (Fig. S6c). All PLE and PL spectra show similar profiles, suggesting that the spectra of Mn²⁺ originate from the same emission center. In addition, the attenuation curves of BMAO:0.6Mn²⁺ at different emission wavelengths were further measured. The lifetimes of BMAO:0.6Mn²⁺ monitored at 500, 515, 530, and 545 nm are in milliseconds, and the single-exponential decay confirms the presence of a single emission source (Fig. S6d). The representative sample in Fig. 2c exhibits a high internal quantum efficiency (IQE) of 94.9% and an external quantum efficiency (EQE) of 18.6% under 455 nm excitation. The higher PLQY of BMAO:0.6Mn²⁺ may be due to the distance between Mn²⁺ ions being large enough to eliminate the coupling of Mn spins.³²

The optical properties of a phosphor at the working temperature are key factors affecting its practical application.⁴⁵ Fig. 2d shows the temperature-dependent PL spectra of BMAO:0.6Mn²⁺ from 303 to 573 K. The results show that the phosphor exhibits normal thermal quenching phenomena, but the PL spectra do not shift significantly with increasing temperature. When heating from 303 to 423 K, the PL intensity of BMAO:0.6Mn²⁺ remains at approximately 90% of its initial intensity, demonstrating excellent thermal stability (Fig. 2e). At the same time, the PL intensities of commercial green powders (Ba, Sr)SiO₄:Eu²⁺ and β-SiAlON:Eu²⁺ at 423 K decrease to 65% and 80% of their initial intensity at 303 K, respectively. These results confirm that the BMAO:0.6Mn²⁺ phosphor has better thermal stability than (Ba, Sr)SiO₄:Eu²⁺ and β-SiAlON:Eu²⁺. As the temperature increases, the FWHM broadens, increasing from 26 to 37 nm (Fig. 2f). The FWHM broadening of the PL spectra can be explained by calculating the Huang–Rhys factor S, as follows:⁴⁶

	(1)

where ħω represents the vibrational phonon energy, S denotes the electron–phonon coupling, and k_B is the Boltzmann constant. The calculated S value of BMAO:0.6Mn²⁺ is 2.22, as shown in Fig. 2g. When 1 < S < 5, it indicates weak electron–phonon coupling in the material, suggesting good thermal stability.⁴⁷ The occurrence of thermal quenching is related to the non-radiative transition of the emission center.⁴⁶ The thermal stability is further analyzed using the Arrhenius equation (Fig. S7). The fitted ΔE value from eqn (S2) is 0.206 eV, suggesting a low probability of non-radiative transitions at high temperatures. Fig. 3h shows the temperature-dependent PL decay curve of the single-exponential fitted BMAO:0.6Mn²⁺. The PL decay curve is slightly reduced from 303 to 573 K. These findings support the good thermal stability of BMAO:0.6Mn²⁺. Fig. 2i shows the change in the PL intensity of the BMAO:0.6Mn²⁺ sample after 20 heating–cooling cycles in the temperature range from 303 to 573 K. After 20 thermal cycles, the PL intensity at 573 K remains at approximately 90%, confirming good repeatability.

2.3. Wide CG backlight display application

A WLED was fabricated using BMAO:0.6Mn²⁺, a commercial KSFM red phosphor, and a blue GaN chip, utilizing the excellent optical properties of BMAO:0.6Mn²⁺. The corresponding electroluminescence (EL) spectrum is shown in Fig. 3a. Note that EL refers to the emission of light by a material under an applied electric field. The correlated color temperature (CCT) and CIE color coordinates are 5339 K and (0.336, 0.341), respectively. The wide color gamut (CG) of the WLED device was calculated to be 125.3% NTSC, which is equivalent to 94.5% Rec.2020 CG (Fig. 3b). Compared with other previously reported green phosphors, the overall performance of the BMAO:0.6Mn²⁺ phosphor is in a leading position (Table S2). In addition, the operating temperature of the device at different currents was tested. Even at a current of up to 320 mA, the optical properties of the BMAO:0.6Mn²⁺ phosphor are hardly affected due to its excellent thermal stability (Fig. 3c). Displays based on BMAO:0.6Mn²⁺ and commercial KSFM phosphors exhibit more vivid and rich color effects compared with traditional commercial displays, which is beneficial for eye health (Fig. 3d and e). These findings offer a promising option for developing high-performance display technologies.

2.4. X-ray 3D imaging application

Broadening the application field of phosphors is conducive to the development of multifunctional materials. The RL spectra of samples with different Mn²⁺-doped concentrations are shown in Fig. S8. It can be seen that the RL intensity of the BMAO:0.6Mn²⁺ sample is the highest. Therefore, the scintillation properties of BMAO:0.6Mn²⁺ under X-ray were studied. As shown in Fig. S9a, the absorption coefficient of the BMAO:0.6Mn²⁺@PDMS film is slightly lower than that of Bi₃Ga₅O₁₂ (BGO), CsI:Tl, and LuAG:Ce³⁺ at the same thickness and size, but the relative light intensity is higher than that of the three commercial scintillation crystals. Specifically, the radioluminescence (RL) intensity is 15.70 times that of BGO and 2.93 times that of CsI:Tl, respectively (Fig. 4a). The prominent RL intensity indicates that the flexible film has a high conversion efficiency for X-rays, which is conducive to low-dose detection and scintillation imaging under X-rays. Fig. S9b shows the RL spectra of the BMAO:0.6Mn²⁺@PDMS film at low dose rates and plots the functional relationship between RL intensity and the dose rate (Fig. 4b). The lowest detection line of the BMAO:0.6Mn²⁺@PDMS film is 35.8 nGy s⁻¹. At an SNR of 3, it is approximately 152 times lower than the current medical X-ray diagnostic requirement of 5.5 μGy s⁻¹.⁴⁸

Fig. 4c clearly shows the light and dark stripes. Fig. 4d shows the change of gray value at different line pairs. The gray value of the line pair card can be clearly distinguished even at 18 lp mm⁻¹. Such a high resolution is directly related to the thickness and transparency of the film. The X-ray imaging device is exhibited in Fig. 4e. The BMAO:0.6Mn²⁺@PDMS film was used as a scintillation screen to image the object placed at the front end and the imaging information was recorded with a digital camera. In Fig. 4f, the thickness of the film measured by a vernier caliper is only 70 μm, and the ‘KUST’ information can be observed very clearly through the film. The film after folding multiple times shows good flexibility and emits bright green light under UV light. As far as we know, the high resolution of the BMAO:0.6Mn²⁺@PDMS film is significantly better than that of most reported single-crystal perovskites, polycrystalline thin films, and quantum-dot glass scintillators. This advantage is attributed to its transparency, suppression of light scattering, and the excellent luminescence efficiency. As shown in Table S3, the BMAO:0.6Mn²⁺@PDMS film stands out for its low detection limit and high X-ray imaging resolution.

As shown in Fig. 4g, the outline of the capsule and the internal metal spring can be clearly observed under X-ray irradiation. The chip with a more complex internal structure can also be clearly imaged. It is worth noting that these high-contrast images are obtained at a dose rate of 3.01 μGy s⁻¹ and an exposure time of 2 s (total radiation dose of 6.02 μGy). This is much lower than the typical chest X-ray diagnostic dose (∼100 μGy). Fig. S9c and S9d record the RL intensity of the flexible film under repeated and continuous X-ray excitation. The RL intensity remains almost unchanged after 80 on/off cycles and continuous irradiation for 30 h, reflecting good long-term operation stability. Compared with flat screens, flexible screens offer better attachment to objects and reduce distortion, which is particularly meaningful for imaging irregular or complex objects. As shown in Fig. 4h, a clearer X-ray image can be obtained by attaching the curved film firmly to the template. This result demonstrates the potential of the prepared flexible film for X-ray 3D imaging.

3. Conclusions

In summary, a series of BMAO:xMn²⁺ phosphors have been synthesized by high temperature solid state sintering. The Mn²⁺-rich phosphors exhibited narrow-band green emission, and their IQE values were as high as 94.9%. The independent Mn²⁺ tetrahedron in the BMAO:0.6Mn²⁺ crystal structure avoids non-radiative energy transfer, enabling efficient luminescence. More importantly, BMAO:0.6Mn²⁺ exhibits outstanding thermal stability, with the peak intensity remaining at 90% at 423 K compared to the intensity at 303 K. The WLED prepared by mixing BMAO:0.6Mn²⁺ with commercial phosphors achieves a wide color gamut of 125.3% of the NTSC 1931 standard and a CCT of 5339 K. In addition, the BMAO:0.6Mn²⁺@PDMS flexible film exhibits good X-ray imaging performance with a resolution of 18.0 lp mm⁻¹ and a detection limit of 35.8 nGy s⁻¹. This excellent BMAO:Mn²⁺ achieves dual-functional applications in the field of solid-state lighting and X-ray imaging.

Author contributions

Heng Dai: writing – original draft, methodology, investigation, and formal analysis. Xinran Wang: methodology and data curation. Zhichao Liu: methodology and formal analysis. Junli Liu: investigation and data curation. Xiuxia Yang: writing – review & editing, supervision, formal analysis, and funding acquisition. Jie Yu: project administration, methodology, investigation, and funding acquisition.

Conflicts of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The data supporting this article have been included as part of the SI.

Experimental section; Crystal structure; XRD spectra; details of Rietveld refinement; SEM imaging; activation energy fitting curve; PLE and PL spectra; XPS spectra; PL decay curves; X-ray absorption coefficients; RL spectra; X-ray irradiation stability; The comparisons of PL properties and scintillation characteristics reported so far. See DOI: https://doi.org/10.1039/d5qi01386k.

Acknowledgements

This work was financially supported by the Yunnan Major Scientific and Technological Projects (202402AB080011), the Special Science and Technology Research Project of Yunnan Province for the South Asia and Southeast Asia Innovation Center (202403AP140006), and the Yunnan Fundamental Research Projects (202501AU070165, 202401BE070001-041).

References

1. M. H. Fang, J. L. Leaño and R. S. Liu, Control of narrow-band emission in phosphor materials for application in light-emitting diodes, ACS Energy Lett., 2018, 3(10), 2573–2586 Search PubMed .
2. M. Zhao, Q. Y. Zhang and Z. G. Xia, Narrow-band emitters in LED backlights for liquid-crystal displays, Mater. Today, 2020, 40, 246–265 CrossRef .
3. H. Liao, M. Zhao, M. S. Molokeev, Q. L. Liu and Z. G. Xia, Learning from a mineral structure toward an ultra-narrowband blue-emitting silicate phosphor RbNa₃(Li₃SiO₄)₄: Eu²⁺, Angew. Chem., Int. Ed., 2018, 57(36), 11728–11731 CrossRef PubMed .
4. X. Liu, R. Li, X. Xu, Y. Jiang, W. Zhu, Y. Yao, F. Li, X. Tao, S. Liu, W. Huang and Q. Zhao, Lanthanide(III)-Cu₄I₄ organic framework scintillators sensitized by cluster-based antenna for high-resolution X-ray imaging, Adv. Mater., 2022, 35(8), 2206741 CrossRef .
5. Q. Chen, J. Wu, X. Ou, B. Huang, J. Almutlaq, A. A. Zhumekenov, X. Guan, S. Han, L. Liang, Z. Yi, J. Li, X. Xie, Y. Wang, Y. Li, D. Fan, D. B. L. Teh, A. H. All, O. F. Mohammed, O. M. Bakr, T. Wu, M. Bettinelli, H. Yang, W. Huang and X. Liu, All-inorganic perovskite nanocrystal scintillators, Nature, 2018, 561, 88–93 CrossRef .
6. Z. G. Xia and A. Meijerink, Ce³⁺-doped garnet phosphors: composition modification, luminescence properties and applications, Chem. Soc. Rev., 2017, 46, 275–299 RSC .
7. L. Wang, R. J. Xie, T. Suehiro, T. Takeda and N. Hirosaki, Down-conversion nitride materials for solid state lighting: recent advances and perspectives, Chem. Rev., 2018, 118(4), 1951–2009 CrossRef .
8. S. Shrestha, R. Fischer, G. J. Matt, P. Feldner, T. Michel, A. Osvet, I. Levchuk, B. Merle, S. Golkar, H. Chen, S. F. Tedde, O. Schmidt, R. Hock, M. Rührig, M. Göken, W. Heiss, G. Anton and C. J. Brabec, High-performance direct conversion X-ray detectors based on sintered hybrid lead triiodide perovskite wafers, Nat. Photonics, 2017, 11, 436–440 CrossRef .
9. J. H. Heo, D. H. Shin, J. K. Park, D. H. Kim, S. J. Lee and S. H. Im, High-performance next-generation perovskite nanocrystal scintillator for nondestructive X-ray imaging, Adv. Mater., 2018, 30(40), 1801743 CrossRef .
10. X. Bai, Z. Xu, Y. Z. Zi, H. P. Zhao, B. K. Zhu, R. B. Feng, Y. K. Cun, A. J. Huang, Y. Liu, Y. W. Li, J. B. Qiu, Z. G. Song, S. J. Langford, J. Y. Liao and Z. W. Yang, Dual-functional X-ray photochromic phosphor: high-performance detection and 3D imaging, Adv. Funct. Mater., 2024, 34(37), 2402452 CrossRef .
11. Z. T. Yang, J. Q. Hu, D. V. der Heggen, A. Feng, H. R. Hu, H. Vrielinck, P. F. Smet and D. Poelman, Realizing simultaneous X-ray imaging and dosimetry using phosphor-based detectors with high memory stability and convenient readout process, Adv. Funct. Mater., 2022, 32(31), 2201684 CrossRef .
12. Y. L. Wang, T. R. Zhou, J. Chen, H. M. Qin, J. H. Wu, Q. Zhang, J. Q. Zheng, X. Li, Y. Y. Sun, Y. H. He, X. Q. Ma, T. T. Ye, R. F. Liu, Z. S. Gao, J. S. Hou, L. J. Wang, H. J. Chen and W. Jiang, Zero-dimensional organic-inorganic hybrid zinc halides for multiple applications in anti-counterfeiting, X-ray imaging and white LEDs, Adv. Opt. Mater., 2024, 12(7), 2301864 CrossRef .
13. Y. H. Yu, S. Y. Liu, J. R. Zhang, W. Zhao, Y. Tang, C. F. Han, X. Y. Chen, L. G. Xu, R. F. Chen, M. G. Li, Y. Tao and W. Z. Lv, Mn(II)-based metal halide with near-unity quantum yield for white LEDs and high-resolution X-ray imaging, Inorg. Chem., 2024, 63(22), 10296–10303 CrossRef PubMed .
14. C. Wang, Z. G. Yan, Y. Wang, J. L. Zhu, C. Peng, Y. Qu, F. Yang, J. W. Xiao and X. D. Han, All-inorganic ruddlesden–popper perovskite Cs₂CdCl₄:Mn for low-dose and flexible X-ray imaging, ACS Mater. Lett., 2024, 6(4), 1429–1438 CrossRef .
15. T. T. Kou, Q. L. Wei, T. Chang, H. Wang, W. Zheng, X. M. Jiang, Q. Zhao, Z. J. Zhou, D. Huang, Z. L. Chen, L. Wang, J. Tang and W. W. Yu, A mild synthesis of 0D Mn²⁺-doped Cs₃CdBr₅ metal halide for white light-emitting diodes and X-ray imaging, Laser Photonics Rev., 2025, 19(2), 2400953 CrossRef .
16. Y. Lv, N. Zhao, W. Q. Li, C. J. Lin, C. J. Chen and J. P. Ueda, Highly stable oxynitride persistent phosphors with widely distributed traps for information storage and anticounterfeiting, Adv. Opt. Mater., 2024, 12(12), 2302580 CrossRef .
17. P. Liu, Y. C. Zhang, B. H. Li, L. Han and Y. Xu, Trap depth engineering in MgGa₂O₄:Bi³⁺ for muticolor dynamic anti-counterfeiting, encryption and optical temperature sensing applications, Chem. Eng. J., 2022, 437(1), 135389 CrossRef .
18. Z. H. Zhou, X. Wang, X. D. Yi, H. Ming, Z. J. Ma and M. Y. Peng, Rechargeable and sunlight-activated Sr₃Y₂Ge₃O₁₂:Bi³⁺ UV–visible–NIR persistent luminescence material for night-vision signage and optical information storage, Chem. Eng. J., 2021, 421(2), 127820 CrossRef .
19. H. M. Li, R. Pang, L. H. Jiang, D. Li, S. Zhang and H. J. Zhang, Exploring the luminescent thermometer and optical storage applications in negative thermal quenching phosphor of BaSc₂Ge₃O₁₀:Pr³⁺, Ceram. Int., 2023, 49(20), 32635–32641 CrossRef .
20. J. W. Zhang, Z. J. Wang, X. X. Huo, Y. Wang and P. L. Li, Multimodal dynamic color-tunable persistent luminescent phosphor Ca₃Al₂Ge₃O₁₂:Mn²⁺, Cr³⁺ for anti-counterfeiting and industrial inspection, Inorg. Chem. Front., 2022, 9, 6517–6526 RSC .
21. C. Liao, F. Liu, H. Wu, H. J. Wu, L. L. Zhang, G. H. Pan, Z. D. Hao, X. J. Wang and J. H. Zhang, Creating deep traps in yttrium aluminum garnet for long-term optical storage and afterglow-intensity-ratio-based temperature sensing, Laser Photonics Rev., 2024, 18(7), 2300924 CrossRef .
22. C. Y. Zhan, H. M. Zhu, S. S. Liang, Y. P. Huang, Z. H. Wang and M. C. Hong, A highly Mn²⁺-doped narrowband green phosphor toward wide color-gamut display applications, Inorg. Chem. Front., 2024, 11, 826–836 RSC .
23. V. Morad, I. Cherniukh, L. Pöttschacher, Y. Shynkarenko, S. Yakunin and M. V. Kovalenko, Manganese(II) in tetrahedral halide environment: factors governing bright green luminescence, Chem. Mater., 2019, 31(24), 10161–10169 CrossRef PubMed .
24. Q. Dong, F. Yang, J. Cui, Y. Tian, S. Liu, F. Du, J. Peng and X. Ye, Enhanced narrow green emission and thermal stability in γ-AlON:Mn²⁺, Mg²⁺ phosphor via charge compensation, Ceram. Int., 2019, 45(9), 11868–11875 CrossRef .
25. E. H. Song, Y. Y. Zhou, Y. Wei, X. X. Han, Z. R. Tao, R. L. Qiu, Z. G. Xia and Q. Y. Zhang, A thermally stable narrow-band greenemitting phosphor MgAl₂O₄:Mn²⁺ for wide color gamut backlight display application, J. Mater. Chem. C, 2019, 7, 8192–8198 RSC .
26. Y. Zhu, Y. Liang, S. Liu, H. Li and J. Chen, Narrow-band green emitting Sr₂MgAl₂₂O₃₆:Mn²⁺ phosphors with superior thermal stability and wide color gamut for backlighting display applications, Adv. Opt. Mater., 2019, 7(6), 1801419 CrossRef .
27. A. Nag, S. Chakraborty and D. D. Sarma, To dope Mn²⁺ in a semiconducting nanocrystal, J. Am. Chem. Soc., 2008, 130(32), 10605–10611 CrossRef PubMed .
28. G. J. Zhou, Z. Y. Liu, J. L. Huang, M. S. Molokeev, Z. W. Xiao, C. G. Ma and Z. G. Xia, Unraveling the near-unity narrow-band green emission in zero-dimensional Mn²⁺-based metal halides: a case study of (C₁₀H₁₆N)₂Zn_1−xMn_xBr₄ solid solutions, J. Phys. Chem. Lett., 2020, 11(15), 5956–5962 CrossRef PubMed .
29. L. J. Xu, C. Z. Sun, H. Xiao, Y. Wu and Z. N. Chen, Green-light-emitting diodes based on tetrabromide manganese(II) complex through solution process, Adv. Mater., 2017, 29(10), 1605739 CrossRef .
30. B. B. Su, M. S. Molokeev and Z. G. Xia, Mn²⁺-based narrow-band green-emitting Cs₃MnBr₅ phosphor and the performance optimization by Zn²⁺ alloying, J. Mater. Chem. C, 2019, 7, 11220–11226 RSC .
31. C. Bertail, S. Maron, V. Buissette, T. Le Mercier, T. Gacoin and J. P. Boilot, Structural and photoluminescent properties of Zn₂SiO₄:Mn²⁺ nanoparticles prepared by a protected annealing process, Chem. Mater., 2011, 23(11), 2961–2967 CrossRef .
32. J. Zhou, Y. Wang, B. Liu and Y. Lu, Effect of H₃BO₃ on structure and photoluminescence of BaAl₁₂O₁₉:Mn²⁺ phosphor under VUV excitation, J. Alloys Compd., 2009, 484(1–2), 439–443 CrossRef .
33. H. Li, Y. Liang, S. Liu, W. Zhang, Y. Bi, Y. Gong and W. Lei, Highly efficient green-emitting phosphor BaZnAl₁₀O₁₇:Mn²⁺ with ultra-narrow band and extremely low thermal quenching for wide color gamut lcd backlights, Adv. Opt. Mater., 2021, 9(24), 2100799 CrossRef .
34. D. Q. Trung, N. Tu, N. V. Quang, M. T. Tran, N. V. Du and P. T. Huy, Non-rare-earth dual green and red-emitting Mn-doped ZnAl₂O₄ phosphors for potential application in plan-growth LEDs, J. Alloys Compd., 2020, 845, 156326 CrossRef .
35. M. Kumar, P. Rajput, P. K. Singh and F. Singh, Luminescence properties of BaMgAl₁₀O₁₇:Mn²⁺ nanophosphors, J. Alloys Compd., 2019, 799, 556–562 CrossRef .
36. V. Singh, G. Sivaramaiah, J. L. Rao, N. Singh, A. K. Srivastava, H. D. Jirimali, J. Li, H. Gao, R. S. Kumaran, P. K. Singh and S. J. Dhoble, Eu²⁺ and Mn²⁺ co-doped BaMgAl₁₀O₁₇ blue- and green-emitting phosphor: A luminescence and EPR study, J. Electron. Mater., 2016, 45, 2776–2783 CrossRef .
37. Q. Wang, M. Liao, Z. F. Mu, X. Zhang, H. F. Dong, Z. J. Liang, J. C. Luo, Y. Yang and F. G. Wu, Ratiometric optical thermometer with high sensitivity based on site-selective occupancy of Mn²⁺ ions in Li₅Zn₈Al₅Ge₉O₃₆ under controllable synthesis atmosphere, J. Phys. Chem. C, 2020, 124(1), 886–895 CrossRef .
38. K. W. Park, H. S. Lim, S. W. Park, G. Deressa and J. S. Kim, Strong blue absorption of green Zn₂SiO₄:Mn²⁺ phosphor by doping heavy Mn²⁺ concentrations, Chem. Phys. Lett., 2015, 636, 141–145 CrossRef .
39. G. Sivakumar, A. Thayyil, M. Munthasir, P. Thilagar and S. Natarajan, Mn-doped Ca₁₄Mg₄Ga₁₂O₃₆ with the tululite mineral structure for color-tunable emission, Chem. Mater., 2024, 36(11), 5356–5369 CrossRef .
40. R. L. Carlin, Inorganic electronic spectroscopy (lever, A.B.P.), J. Chem. Educ., 1969, 46, A628 CrossRef .
41. X. R. Xu and M. Z. Su, Luminescence and Luminescent Materials, Chemical Industry Press, Beijing, 2004 Search PubMed .
42. X. Zhou, J. Xiang, J. Zheng, X. Zhao, H. Suo and C. Guo, Ab initio two-sites occupancy and broadband near-infrared emission of Cr³⁺ in Li₂MgZrO₄, Mater. Chem. Front., 2021, 5, 4334–4342 RSC .
43. M. Zhao, H. Liao, M. S. Molokeev, Y. Zhou, Q. Zhang, Q. Liu and Z. Xia, Emerging ultra-narrow-band cyan-emitting phosphor for white LEDs with enhanced color rendition, Light: Sci. Appl., 2019, 8, 38 CrossRef PubMed .
44. S. Wang, X. Han, T. Kou, Y. Zhou, Y. Liang, Z. Wu, J. Huang, T. Chang, C. Peng, Q. Wei and B. Zou, Lead-free MnII-based red-emitting hybrid halide (CH₆N₃)₂MnCl₄ toward high performance warm WLEDs, J. Mater. Chem. C, 2021, 9, 4895–4902 RSC .
45. Y. H. Kim, P. Arunkumar, B. Y. Kim, S. Unithrattil, E. Kim, S. H. Moon, J. Y. Hyun, K. H. Kim, D. Lee, J. S. Lee and W. B. Im, A zero-thermal-quenching phosphor, Nat. Mater., 2017, 16, 543 CrossRef PubMed .
46. Y. Dai, Q. Wei, T. Chang, J. Zhao, S. Cao, B. Zou and R. Zeng, Efficient self-trapped exciton emission in ruddlesden–popper Sb-doped Cs₃Cd₂Cl₇ perovskites, J. Phys. Chem. C, 2022, 126(27), 11238–11245 CrossRef .
47. K. Huang and Z. Gu, Phonon analysis in multiphonon transitions, Commun. Theor. Phys., 1982, 1(5), 535–555 CrossRef .
48. W. Zhu, W. Ma, Y. Su, Z. Chen, X. Chen, Y. Ma, L. Bai, W. Xiao, T. Liu, H. Zhu, X. Liu, H. Liu, X. Liu and Y. Yang, Low-dose real-time X-ray imaging with nontoxic double perovskite scintillators, Light: Sci. Appl., 2020, 9, 112 Search PubMed .

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