Synthesis, persistent luminescence, and thermoluminescence properties of yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce, Nd, Dy, Ho, Er, Tm, Yb) and orange-red Sr(3-x)Ba(x)SiO5:Eu2+, Dy3+ phosphor

The effects of Lu3+, Gd3+ and Ga3+ substitution on the photoluminescence of Y2.95-x-yLuxGdyAlzGa5-zO12:0.05Ce3+ phosphors for high-power white AC-LEDs

Various yellowish-green persistent phosphors of Y2.95-x-yLuxGdyAl5-zGazO12:0.05Ce3+ (x = 0-1, y = 0-1, z = 1-4) were successfully synthesized by the one-step high-temperature solid-state reaction method in air. The effects of simultaneous doping of Lu3+, Gd3+ and Ga3+ on the luminescence properties of the phosphors were investigated in detail for the first time. Herein, the microstructure, morphology, afterglow performance, luminescence properties, thermoluminescence, thermal quenching and flicker index of the efficient blue-light-activated Y2.95-x-yLuxGdyAl5-zGazO12:0.05Ce3+ phosphors were tested. The τ90 and τ80 values of Y1.45LuGd0.5Al2.5Ga2.5O12:0.05Ce3+ are 10.8 ms and 33.2 ms, respectively. These parameters are important in terms of effectiveness in reducing flicker in alternating current (AC) LEDs. Compared with the conventional Y3Al2Ga3O12:Ce3+ phosphor, the Y1.45LuGd0.5Al2.5Ga2.5O12:0.05Ce3+ phosphor has a better luminescence performance, stronger afterglow performance, and lower flicker index. The quantum yield of the Y1.45LuGd0.5Al2.5Ga2.5O12:0.05Ce3+ phosphor was 86.42% and the luminous efficiency of the LED devices prepared with it reached 92.12 lm W-1 when operated at 100 mA. Integrating sphere and spectroradiometer tests as well as CIE chromaticity diagrams indicate that the AC-WLEDs assembled by mixing the Y1.45LuGd0.5Al2.5Ga2.5O12:0.05Ce3+ phosphor and a commercial red phosphor in an appropriate ratio could obtain ideal white light with a high color-rendering index (87.9) and the flickering index was successfully reduced from 100% to 61.4%.

Research Advances on Human-Eye-Sensitive Long Persistent Luminescence Materials

Based on the actual application requirements of multicolor long persistent luminescence (LPL) materials, we highlight the recent developments in the last decade on human-eye-sensitive LPL materials and try to make a full list of known LPL compounds possessing wavelengths of 400-600 nm and a duration time longer than 10 h (>0.32 mcd/m²); these are more sensitive to the human eye's night vision and can be used throughout the night. We further emphasize our group research of novel LPL materials and the regulation of LPL color to enable a full palette. In the end, we try to summarize the challenges and perspectives of LPL materials for potential research directions based on our limited understandings. This review could offer new enlightenment for further exploration of new LPL materials in the visible light range and related applications.

Color-Tunable Persistent Luminescence of Ca10M(PO4)7:Eu2+ (M = Li, Na, and K) with a β-Ca3(PO4)2-Type Structure

Eu²⁺-activated Ca₁₀M(PO₄)₇ (M = Li, Na, and K) phosphates have been explored extensively because of their tunable emission wavelengths and excellent luminescence performances. Herein, the persistent luminescence (PersL) properties of Eu²⁺-doped Ca₁₀M(PO₄)₇ phosphors with a β-Ca₃(PO₄)₂-type structure are reported. With the variation of alkali metal M from Li to Na and to K, the PersL color can be adjusted sequentially from yellow to white and to blue, and the persistent durations are prolonged significantly from about ∼61 s for Ca_9.997Li(PO₄)₇:0.003Eu²⁺ to ∼1950 s for Ca_9.999Na(PO₄)₇:0.001Eu²⁺ and to ∼7440 s for Ca_9.9995K(PO₄)₇:0.0005Eu²⁺ at the threshold value (0.32 mcd/m²) after 254 nm irradiation. The trap depths are estimated according to the thermoluminescence glow curves with various heating rates. Comparing the thermoluminescence excitation and photoluminescence excitation spectra, it can be verified that there are two sources of ionized electrons in the charging process: one is excited from the valence band to the conduction band (CB) and the other is excited from the 4f ground state of Eu²⁺ to the higher 5d levels or directly to the CB. Finally, the PersL mechanism is proposed. This work is expected to motivate more research of Eu²⁺-doped phosphate-based PersL materials, as well as contributes to the understanding of the PersL mechanism of Eu²⁺-doped phosphors.

Antiperovskites with Exceptional Functionalities

ABX₃ perovskites, as the largest family of crystalline materials, have attracted tremendous research interest worldwide due to their versatile multifunctionalities and the intriguing scientific principles underlying them. Their counterparts, antiperovskites (X₃ BA), are actually electronically inverted perovskite derivatives, but they are not an ignorable family of functional materials. In fact, inheriting the flexible structural features of perovskites while being rich in cations at X sites, antiperovskites exhibit a diverse array of unconventional physical and chemical properties. However, rather less attention has been paid to these "inverse" analogs, and therefore, a comprehensive review is urgently needed to arouse general concern. Recent advances in novel antiperovskite materials and their exceptional functionalities are summarized, including superionic conductivity, superconductivity, giant magnetoresistance, negative thermal expansion, luminescence, and electrochemical energy conversion. In particular, considering the feasibility of the perovskite structure, a universal strategy for enhancing the performance of or generating new phenomena in antiperovskites is discussed from the perspective of solid-state chemistry. With more research enthusiasm, antiperovskites are highly anticipated to become a rising star family of functional materials.

Enhancement of long-lived luminescence in nanophosphors by surface defect passivation

We found that surface defects quenched the persistent luminescence in nanophosphors, and surface passivation can improve the persistent luminescence efficiency.

Sr3YLi(PO4)3F:Eu2+,Ln3+: colorless-magenta photochromism and coloration degree regulation through Ln3+ co-doping

Herein, novel photochromic materials, Sr₃YLi(PO₄)₃F:Eu²⁺,Ln³⁺, have been prepared by a conventional high-temperature solid-state reaction.

Tunable emission color and mixed valence state via the modified activator site in the AlN-doped Sr3SiO5:Eu phosphor

Mixed valence states of Eu²⁺/Eu³⁺ and tunable emission colors were obtained based on the activator-site modification in the AlN co-doped Sr₃SiO₅:Eu phosphor.

Long persistent phosphors—from fundamentals to applications

We present multidisciplinary research on synthetic methods, afterglow mechanisms, characterization techniques, material kinds, and applications of long persistent phosphors.

Design, synthesis and characterization of near-infrared long persistent phosphors Ca4(PO4)2O:Eu2+,R3+ (R = Lu, La, Gd, Ce, Tm, Y)

Eu²⁺-activated phosphate NIR long persistent phosphors.

Bandgap Tailoring via Si Doping in Inverse-Garnet Mg3Y2Ge3O12:Ce(3+) Persistent Phosphor Potentially Applicable in AC-LED

The state-of-the-art alternating-current light-emitting diode (AC-LED) technique suffers from adverse lighting flicker during each AC cycle. Aiming to compensate the dimming time of AC-LED, herein, we report a novel Mg3Y2(Ge1-xSix)3O12:Ce(3+) inverse-garnet persistent phosphor whose afterglow is efficiently activated by blue light with persistent luminescence in millisecond range. It is experimentally demonstrated that Si doping tailors the host bandgap, so that both the electron charging and detrapping in the persistent luminescence process are optimized. To explore the origin of the millisecond afterglow, we performed a series of thermoluminescence analyses, revealing three types of continuously distributed traps in the host. Finally, an AC-LED prototype device was fabricated, which exhibits the warm white emission with a reduced percent flicker of 71.7%. These results demonstrate that the newly developed persistent phosphor might be a promising candidate applicable in low flickering AC-LED which has advantages of cheaper price, longer lifetime, and higher energy utilization efficiency.

Optically stimulated persistent luminescence of europium-doped LaAlO3 nanocrystals

Persistent luminescence associated with Eu³⁺ in LaAlO₃:Eu³⁺ nanocrystals can be observed and enhanced by optical stimulation.

Low-temperature VUV photoluminescence and thermoluminescence of UV excited afterglow phosphor Sr3AlxSi1−xO5:Ce3+,Ln3+ (Ln = Er, Nd, Sm, Dy and Tm)

Low-temperature thermoluminescence measurements of Ce doped Sr₃SiO₅ show that Ce³⁺ is the recombination centre and Nd, Sm, Dy and Tm work as electron traps with trap depths of 0.95 eV, 1.89 eV, 1.02 eV, and 1.19 eV, respectively.