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Spinel configuration is a kind of broadly considered host candidate when designing persistent luminescence (PersL) materials due to the easy generation of vacancies and anti‐site defects. Here, a new strategy of defect enrichment for the activation of PersL is proposed, and in contrast to the spinel configuration, it is demonstrated that the crystal structure of near inverse spinel ensures more numerous defects to activate the near‐infrared (NIR) PersL of Fe3+. Fe3+‐doped MgGa2O4 displays the PersL band in the range of 600 to 900 nm and possesses a super‐long PersL duration time >15 h. The optical analysis and the calculation of density functional theory unravel that the near inverse spinel structure can lower the carrier transfer barriers to accelerate the formation of carrier trap states within the bandgap. Therefore, more numerous defects in this structure may participate in the trapping and de‐trapping process by comparison with the normal spinel configuration. These findings are expected to accelerate the development of new PersL materials through Fe3+ doping toward versatile biological applications in NIR window. [ABSTRACT FROM AUTHOR]

Currently, most of the mechanoluminescence (ML) phosphors strongly depend on postirradiation stimulation using ultraviolet light (denoted as "UV exposure" from hereon) to show the ML. However, only a few transition metal cations are proven to be effective luminescence centers, which hinder the development of more ML phosphors. This study reports a self‐recoverable deep‐red‐to‐near‐infrared ML using Cr3+‐doped LiGa5O8 phosphor with fully recoverable ML performance. The ML performance can be further optimized by tuning the trap redistributions by codoping the phosphor with Al3+ and Cr3+ cations. Theoretical calculations reveal the important role of Cr dopants in the modulation of local electronic environments for achieving the ML. Owing to the induced interelectronic levels and shallow electron trap distributions, the electron recombination efficiency is enhanced both through direct tunneling and energy transfer toward the dopant levels. Moreover, the ML of Cr3+‐doped LiGa5O8 can penetrate a 2‐mm‐thick pork slice, showing that it can have wide‐ranging in vivo applications, including the optical imaging of intracorporal stress/strain distribution and dynamics. Therefore, this work fabricates a novel ML material with self‐recoverable luminescence in an extended wavelength range, increasing the number of potential ML candidates and promoting the fundamental understanding and practical applications of ML materials. [ABSTRACT FROM AUTHOR]

Red luminescent phosphor SrLaGa3O7:Mn4+ was prepared by the traditional high-temperature solid-state reaction. The structural characteristics, luminescence properties and the performance of this phosphor were investigated in light-emitting diode devices. Deep red emission peaking at ∼715 nm was observed under the excitation wavelength in the range of 220–550 nm, which is related to the charge transfer band of Mn4+–O2− and the 4A2g → 4T1g, 4A2g → 2T2g and 4A2g → 4T2g transitions of Mn4+. In particular, SrLaGa3(1−x) O7:3xMn4+ exhibits the strongest absorption in the near ultraviolet region (350–410 nm). This feature can well match the emission of current commercial near-ultraviolet chips, and is expected to be used in white LEDs. Moreover, we also conducted a thermal quenching experiment on the SrLaGa3O7:Mn4+ phosphor, and the obtained activation energy was 0.4 eV, indicating that the quenching temperature is (T50%) 370 K. Finally, the application of the SrLaGa3O7:Mn4+ phosphor in constructing a LED device was explored. At a driving current of 20 mA, the Commission on Illumination (CIE) coordinates of the device are (0.3281, 0.3080), with a high color rendering index (CRI) of 91.9 and a low corresponding color temperature (CCT) of 4315 K. Experimental results show that the phosphor has broad prospects in preparing white LED devices excited by near-ultraviolet light. [ABSTRACT FROM AUTHOR]

The luminescence characteristics of Bi3+ ions in solids have been extensively investigated during recent decades; however, the origin of extra spectra signals (referred to as D-bands) of Bi3+ in some compounds still remains ambiguous. In this work, a novel Bi3+-doped phosphor La3SnGa5O14:Bi3+ (LSGO:Bi3+) was successfully synthesized via the conventional solid-state reaction method. The structural characteristics, luminescence properties and concentration quenching of the LSGO:Bi3+ phosphor were investigated systematically and two emission bands centered at 360 and 540 nm were observed, respectively. The narrow band emission centered at 360 nm was attributed to the transition of 3P1 → 1S0 (A-band) of Bi3+ while the broadband emission centered at 540 nm was considered as the D-band emission. A combined experimental and theoretical approach was employed in order to confirm the origin of the D-band emission of LSGO:Bi3+. Temperature dependent photoluminescence of LSGO:Bi3+ and the fluorescence lifetime of two emission centers were studied. Moreover, the energy of metal-to-metal charge-transfer (MMCT) was also calculated. Ultimately, the D-band emission of LSGO:Bi3+ was considered to originate from the forbidden 3P0 → 1S0 electronic transition of Bi3+. This work will contribute to a better understanding of the luminescence mechanisms of Bi3+ doped phosphors and pave the way toward the future development of new effective Bi3+ activated luminescent materials. [ABSTRACT FROM AUTHOR]

In this study, a blue fluorescent material Sr3Y(BO3)3:Bi3+ was synthesized by the high temperature solid-state reaction method. The corresponding structural characteristics, concentration and temperature dependent luminescence characteristics of Sr3Y(BO3)3:Bi3+ and the LED device performances were systematically studied. At different excitation wavelengths in the range of 340–375 nm, the photoluminescence (PL) region can be adjusted from green (CIE: (0.2524, 0.4063); Peak: 511 nm) to blue (CIE: (0.1936, 0.1236); Peak: 415 nm). The best excitation peaked at ∼370 nm, which well matches with the emission of a commercial near-ultraviolet (NUV) light-emitting diode (LED) chip. The thermal quenching experiment was performed, and the activation energy was calculated as 0.23 eV. At high temperature, the Sr2.55Y(BO3)3:0.45Bi3+ phosphor presented good thermal stability (79.99% of RT emission intensity at 420 K). LED devices (chip: 370 nm) using the Sr2.55Y(BO3)3:0.45Bi3+ phosphor as a fluorescent material showed excellent electroluminescence performance. Under a driving current of 20 mA, the devices showed CIE coordinates of (0.3842, 0.3980), a correlated color temperature (CCT) of 4053 K and a high color rendering index (Ra) of 91.6. This work demonstrates that Sr3Y(BO3)3:Bi3+ is a promising NUV excited blue fluorescent material which shows advantage in white light-emitting diodes for solid-state lighting. [ABSTRACT FROM AUTHOR]

Bismuth (Bi)‐doped photonic glasses and fibers with broadband near‐infrared (NIR) photoemission have potential applications in tunable lasers and broadband amplifiers. Yet, when it comes to all wavelength amplification of optical communication, it remains challenging to achieve efficient Bi NIR emission in the technically relevant C‐ and L‐ bands (1530‐1625 nm). Here, we propose a scheme by fluorination triggered enhancement of ultra‐broadband Bi NIR emission in nitrided germanate glasses. Besides, compared to previous research, a unique and efficient Bi‐activated ultra‐wideband NIR emission with new emission bands peaked at ~924 and ~1520 nm under excitation of 450 nm are obtained in nitrided germanate glasses after fluorination. Moreover, the fluorination can modulate the local chemical environment by forcing the conversion of aluminum species from AlO4 to AlO5 and AlO6 and consequently increase the flexibility of the glass network structure, which finally induces the conversion of Bi species and then manipulates the relative emission intensity of different Bi NIR centers. Thus, a flat and tunable emission spectrum covering the entire optical communication band is obtained by optimizing the fluoride amount. We believe this work is helpful to design the Bi‐doped tunable fiber lasers and ultra‐broadband amplifiers for all wavelength amplification of optical communication. [ABSTRACT FROM AUTHOR]

In this paper, a blue-emitting phosphor CaYGaO4:Bi3+ is reported, which has a broad emission band peaked at 435 nm covering the 375 nm to 575 nm spectral region. The CIE coordinates of CaYGaO4:Bi3+ is (0.1536, 0.0885) with color purity of 85.2%. Importantly, when Bi3+ ions are introduced into the CaYGaO4 host, the excitation peak of Bi3+ is located at 370 nm, which matches well with the efficient near-ultraviolet (NUV) light emitting diode (LED) chips. Furthermore, the emission intensity of the CaYGaO4:Bi3+ phosphor increased ∼1.47 times by adding Li2CO3 as a fluxing agent. The quantum efficiency of the prepared CaYGaO4:Bi3+,Li+ phosphor reaches 45.7% under 370 nm excitation, and the PL intensity remains 76.3% of that at room temperature at 423 K. Using the CaYGaO4:Bi3+,Li+ phosphor, coupled only with an orange phosphor (Sr,Ba)3SiO5:Eu2+ and a 370 nm NUV chip driven by 20 mA current, a NUV-based WLED, with chromaticity coordinates of (0.3610, 0.3360), correlated color temperature (CCT) = 4304 K and color rendering index (CRI) = 86.9, has been achieved. The white light emitting diodes employing CaYGaO4:Bi3+ as a blue-emitting component exhibit superior electroluminescence properties. All results demonstrate that CaYGaO4:Bi3+ is a promising blue component for application in NUV-based WLEDs. [ABSTRACT FROM AUTHOR]

A blue emitting phosphor Na2Y2B2O7:Bi3+ was synthesized by a solid state reaction method. The structure characteristics, concentration, temperature-dependent luminescence and light emitting diode (LED) device performance were systematically studied. Adjustable photoluminescence (PL) from blue to green under different excitation wavelengths from 320 to 390 nm was observed, which is attributed to the complex energy transfer between multiple Bi3+ centres. Moreover, strong absorption in the near ultraviolet region (350–400 nm) was observed in Na2Y2B2O7:Bi3+, which is desirable for LEDs excited by near ultraviolet chips. In addition, a thermal quenching experiment was carried out and the calculated activation energy was 0.28 eV, indicating that this new Na2Y2B2O7:Bi3+ phosphor has good thermal stability. Finally, we explored the application of the Na2Y2B2O7:Bi3+ phosphor by encapsulating LED devices. The device Commission of Illumination (CIE) coordinates are (0.3572, 0.3407), and a high color rendering index (CRI) of 91.1 and a low corresponding color temperature (CCT) of 4480 K under 60 mA current were recorded. These characteristics show that this phosphor can be used to prepare white LED devices excited by near ultraviolet chips. [ABSTRACT FROM AUTHOR]

Till now, many doped persistent luminescence (PersL) phosphors have been investigated and found various applications in such as bioimaging, photocatalysis and information storage, but introducing PersL emitters into a proper host is mostly complex. In this research, a self‐activated PersL phosphor Ba2Zr2Si3O12 (BZSO) is prepared by solid state reaction. By adding NH4Cl, the self‐activated PersL intensity is evidently enhanced. The trap depths and concentrations are examined by thermoluminescence spectra. Meanwhile, Bi3+ ions are introduced into BZSO and show wide band photoluminescence (PL) from 300 to 600 nm. Moreover, the PL of Bi3+ is tunable under excitation by 265‐350 nm lights. Furthermore, as a proof‐of‐concept design, we designed a patterned quick response (QR) code based on the self‐activated PersL of BZSO, and the information of "South China University of Technology (SCUT)" can be read out by the code scanning technology. Bi3+‐doped BZSO phosphors are suggested to provide potential applications in information storage by its self‐activated PersL, and to excite researchers to study the tunable PL in Bi3+‐doped phosphor. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) persistent luminescence (PersL) materials have recently evoked considerable interest in the field of biomedicine, but the choices of efficient emitters for NIR PersL phosphors are rather limited. Herein, we report a new class of Fe3+-activated NIR PersL phosphor based on the LiGaO2 host, which exhibits an intense NIR PersL at around 748 nm and possesses an ultra-long PersL time of much longer than 26 h. The optical properties of this phosphor as well as the trapping and de-trapping processes, the trap characteristics, and the underlying PersL mechanism are comprehensively studied by means of photoluminescence (PL), PersL, electron paramagnetic resonance (EPR), thermoluminescence (TL), and X-ray photoelectron spectroscopies (XPS). It was found that the NIR PersL in this material is closely related to the oxygen vacancies. Furthermore, the penetration experiments and cytotoxicity tests of the biological tissue show that this material has great potential for bioimaging applications. Our achievement in the case of nontoxic Fe3+-activated LiGaO2 phosphors lays the foundation for the future design of Cr3+-free PersL phosphors with efficient NIR PersL towards versatile bioapplications. [ABSTRACT FROM AUTHOR]

A narrow-band emitting phosphor is essential for high performance liquid crystal display (LCD) backlights. However, most of the narrow-band emitting phosphors are only realized by doping Eu or Mn ions, which limits the optional range. Especially, the discovery of narrow-band blue-emitting phosphors without resorption in the visible light region is still challenging. Herein, an emerging rare-earth free and narrow-band blue-emitting phosphor, Y3Al2Ga3O12:Bi3+, with high color purity (up to 90.9%) has been discovered via selective excitation for the first time. The luminescence properties such as photoluminescence (PL), photoluminescence excitation (PLE) and lifetime spectra were systematically investigated. The sample exhibited tunable emission ranging from red to green and then to blue under variable excitation, originating from four Bi luminescence centers. Y3Al2Ga3O12:Bi3+ exhibits a narrow-band blue emission centered at 410 nm with a full width at half maximum of 39 nm and strong absorption in the range of 260–380 nm, which matches well with the commercial near-ultraviolet (NUV) chip. What's more, the sample shows remarkable thermal stability, retaining 90.71% of its room temperature emission intensity at 420 K. In this work, a rare-earth free narrow-band blue-emitting phosphor has been discovered for the first time. [ABSTRACT FROM AUTHOR]

Thermal quenching of phosphor is an important challenge for its practical application in phosphor‐converted white light‐emitting diodes (pc‐WLEDs) and it usually becomes aggravated with the increase of activator concentration. Conversely, this work finds the thermal quenching of Eu2+ emission at 490 nm in Sr4Al14O25:Eu2+ does not follow this in the temperature range of 300 to 480 K, and the rate of it is even slowed down as the concentration of Eu2+ increases. However, at the same time, the experiment on three heating‐cooling cycles of Sr4Al14O25:Eu2+ reveals that the thermal degradation of Eu2+ emission becomes improved. Once Eu2+ ions are doped into Sr4Al14O25, they will prefer substituting for the 10‐ and 7‐coordinated strontium sites Sr1 and Sr2, respectively. The emission centers Eu1 and Eu2, therefore, appear. The abnormal phenomenon is perhaps partly due to the enhanced energy transfer from the emission center Eu1 at 407 nm to the one Eu2 at 490 nm. It is also found interesting that the introduction of AlN can enhance the emission of Sr4Al14O25:Eu2+ without leading to the deterioration of thermal degradation. In the end, a prototype of pc‐WLED was fabricated with Sr4Al14O25:Eu2+ to demonstrate the application of white lighting. This work is not only beneficial to the understanding of the relationship between concentration and thermal quenching, but also conducive to the design of the heavily doped phosphor for WLEDs with better resistance to thermal quenching. [ABSTRACT FROM AUTHOR]

To avoid color drift WLEDs at high temperatures, it is important to develop color stable luminescent materials. Herein, we have reported a phosphor YTaO4:Bi3+ with stable blue emission upon ultraviolet excitation even during the temperature changes between 300 and 480 K. Upon excitations into host absorptions, tunable blue emission can be observed from 400 nm to 450 nm due to the enhanced energy transfer efficiency from the host to bismuth ions as the concentration of bismuth increases. As the excitation scheme is modulated between 355 and 370 nm, white emission can be achieved in YTaO4 singly doped with Bi3+, which has rarely been reported previously. As a proof-of-concept study, prototype WLEDs have been developed with phosphor YTaO4:Bi3+ and 365 nm InGaN chips under different driving currents. Our findings make it possible to develop single-phase white light-emitting phosphors activated by single Bi3+ ions for WLEDs and can also inspire the development of WLED devices with high chromatic stability. [ABSTRACT FROM AUTHOR]