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Converting mechanical energy into photon emission provides a promising route for intelligent sensing, self‐powered lighting, and distributed energy harvesting, which is of great significance for finding a feasible solution to the current sensing technical bottleneck and energy crisis. As the basis for understanding the conversion mechanism and realizing high‐frequency mechanical energy utilization, elucidating the dynamic process of intensity variation in the mechano‐to‐photon conversion remains a great challenge. Herein, a time‐domain characterization scheme that enables to unravel the intrinsic decay of mechanoluminescence (ML) with lifetimes from milliseconds down to tens of microseconds is constructed. It is demonstrated that ML decay characterization is an important tool to reveal the dynamics of charge migration in ML materials. The ML decay in a typical self‐reproducible ML material ZnS:Mn2+ shows temperature dependence and stress fluctuation resistance, which opens up a new reliable approach for self‐powered and remote temperature sensing. Finally, benefiting from the shortest ML lifetime recorded to date, an ultrafast‐response stress sensor that enables to detect individual pulses of ultrasonic waves with ML sensing technology is developed. [ABSTRACT FROM AUTHOR]

White light‐emitting diodes (WLEDs) for road lighting are required to have both the high scotopic to photopic ratio (S/P) and color rendering index (CRI). However, there is a trade‐off between S/P and CRI, and WLEDs commonly having the S/P of 1.68‐2.38 usually exhibit a low CRI. In this work, to provide a best solution to the trade‐off problem we proposed an optimal spectral model for the phosphor‐converted WLEDs (pc‐WLEDs) aiming to figure out the optimal phosphor combination. The Monte Carlo Algorithms combined with the Genetic Algorithm were adopted to obtain the optimization of CRI and S/P by varying the spectral power distributions of WLEDs through adjusting the spectral parameters. Considering the spectral requirements of pc‐WLEDs based on the mesopic vision, we chose CaAlSiN3:Eu2+ and Y3(Ga,Al)5O12:Ce3+ as the red‐ and green‐emitting phosphors to prepare WLEDs with both high S/P and CRI, respectively. The simulation based on the optimal spectral model led to an optimal pc‐WLED with a high S/P of 2.0‐2.14, Ra > 80 and correlated color temperature (CCT) of 4000‐5000 K, which matches very well with the experimental results of S/P = 2.064, Ra = 93.9, and CCT = 4981 K for the two‐phosphor converted WLEDs. It implies that the optimal spectral model would be used effectively for the spectral design and phosphor selection for WLEDs. [ABSTRACT FROM AUTHOR]

Abstract: The fast‐growing amount of data that is produced every year creates an urgent need for ultracapacity storage media. However, 2D spatial resolution in the conventional optical data storage media has almost reached the limit. Further enlargement of storage capacity may rely on the development of the next‐generation data storage materials containing multiplexed information dimensions. Herein, a series of novel deep‐trap persistent luminescence materials (Sr1‐xBax)Si2O2N2:Eu/Yb,Dy with multicolor emissions in the whole visible region is developed and demonstrated a bit‐by‐bit optical data storage and readout strategy based on photon trapping and detrapping processes in these materials. Optical data can be handily encoded on a flexible film by a commercially available 405 nm laser and decoded by heating or by 980 nm laser scanning. The decoded information contains tunable spectral characteristics, which allows for the emission–intensity–multiplexing or emission–wavelength–multiplexing. The storage and readout strategy not only shows a great promise in the application of multidimensional rewritable optical data storage, but also opens new opportunities for advanced display technology and information security system. [ABSTRACT FROM AUTHOR]

Luminescence degradation under moisture and thermal attacks during the term of service cannot be ignored for phosphors used in solid state lighting. In this work, the moisture-assisted thermal degradation of two commercially available red phosphors (Ca1−xSrx)AlSiN3:Eu2+ with different Sr/Ca ratios (RP625: Sr/Ca = 0.9/0.1; RP660: Sr/Ca = 0/1) was investigated by treating phosphor powders at 170–230 °C for 8–96 h in pressurized water steam. The experimental results show that the chemical composition has a great impact on the thermal stability of (Ca1−xSrx)AlSiN3:Eu2+, and a lower Sr/Ca ratio results in a smaller thermal degradation. The activation energies for thermal degradation are 66.26 and 72.13 kJ mol−1 for RP625 and RP660, respectively. The phase transformation, microstructure evolutions, diffuse reflectance spectra, photoluminescence and cathodoluminescence spectra of samples before and after thermal treatment were discussed to reveal the thermal degradation mechanism. The serious degradation observed in RP625 is caused by the decomposition of the phosphor host and the oxidation of the Eu2+ dopant, which is closely related to the increased bond length of Sr/Ca/Eu–N chemical bonds. [ABSTRACT FROM AUTHOR]

In this work we reported novel Yb-doped (Ba1−xSrx)AlSi5O2N7 phosphors showing intense persistent luminescence (PersL) in the visible and near-infrared (NIR) regions simultaneously. Both Yb2+ and Yb3+ were found to be PersL emitters, which presented a broad emission band centered at 664 nm and a sharp emission at 980 nm, respectively. The radiance of PersL in the Ba0.8Sr0.2AlSi5O2N7:Yb phosphor at 60 min after ceasing UV irradiation was 4.82 × 10−3 mW Sr−1 m−2, approximately one-third of the well-known ZnGa2O4:Cr3+ PersL phosphor. The results demonstrate that Yb could be a promising red-to-NIR PersL emitter and more Yb-activated phosphors could be developed for red-to-NIR PersL. [ABSTRACT FROM AUTHOR]

A series of Ce 3+ -, Tb 3+ - and Ce 3+ /Tb 3+ -doped La 3 Si 8 N 11 O 4 phosphors were synthesized by gas-pressure sintering (GPS). The energy transfer between Ce 3+ and Tb 3+ occurred in the co-doped samples, leading to a tunable emission color from blue to green under the 360 nm excitation. The energy transfer mechanism was controlled by the dipole-dipole interaction. The Ce 3+ /Tb 3+ co-doped sample had an external quantum efficiency of 46.7%, about 5.6 times higher than the Tb-doped La 3 Si 8 N 11 O 4 phosphor (8.3%). The thermal quenching of the Tb 3+ emission in La 3 Si 8 N 11 O 4 :Tb,Ce was greatly reduced from 74 to 30% at 250 °C, owing to the energy transfer from Ce 3+ to Tb 3+ . The blue-green La 3 Si 8 N 11 O 4 :0.01Ce,0.05Tb phosphor was testified to fabricate a warm white LED that showed a high color rendering index of 90.2 and a correlated color temperature of 3570 K. The results suggested that the co-doped La 3 Si 8 N 11 O 4 :Ce,Tb phosphor could be a potential blue-green down-conversion luminescent material for use in UV-LED pumped wLEDs., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Deep-trap persistent luminescent materials, due to their exceptional ability of energy storage and controllable photon release under external stimulation, have attracted considerable attention in the field of optical information storage. Currently, the lack of suitable materials is still the bottleneck that restrains their practical applications. Herein, we successfully synthesized a series of deep-trap persistent luminescent materials Y 3 Al 5- x Ga x O 12 :Ce 3+ ,V 3+ ( x = 0-3) with a garnet structure and developed novel phosphor-in-glass (PiG) films containing these phosphors. The synthesized PiG films exhibited sufficiently deep traps, narrow trap depth distributions, high trap density, high quantum efficiency, and excellent chemical stability, which solved the problem of chemical stability at high temperatures in the reported phosphor-in-silicone films. Moreover, the trap depth in the phosphors and PiG films could be tailored from 1.2 to 1.6 eV, thanks to the bandgap engineering effect, and the emission color was simultaneously changed from green to yellow due to the variation of crystal field strength. Image information was recorded on the PiG films by using a 450 nm blue-light laser in a laser direct writing mode and the recorded information was retrieved under high-temperature thermal stimulation or photostimulation. The Y 3 Al 5- x Ga x O 12 :Ce 3+ ,V 3+ PiG films as presented in this work are very promising in the applications of multidimensional and rewritable optical information storage.

Deep-trap persistent luminescence materials exhibit unique properties of energy storage and controllable photon release under additional stimulation, allowing for both wavelength and intensity multiplexing to realize high-capacity storage in the next-generation information storage system. However, the lack of suitable persistent luminescence materials with deep traps is the bottleneck of such storage technologies. In this study, we successfully developed a series of novel deep-trap persistent luminescence materials in the Ln 2+ /Ln 3+ -doped SrSi 2 O 2 N 2 system (Ln 2+ = Yb, Eu; Ln 3+ = Dy, Ho, Er) by applying the strategy of trap depth engineering. Interestingly, the trap depth can be tailored by selecting different codopants, and it monotonically increases from 0.90 to 1.18 eV in the order of Er, Ho, and Dy. This is well explained by the energy levels indicated in the host-referred binding energy scheme. The orange-red-emitting SrSi 2 O 2 N 2 :Yb,Dy and green-emitting SrSi 2 O 2 N 2 :Eu,Dy phosphors are demonstrated to be good candidates of information storage materials, which are attributed to their deep traps, narrow thermoluminescence glow bands, high emission efficiency, and excellent chemical stability. This work not only validates the suitability of deep-trap persistent luminescence materials in the information storage applications, but also broadens the avenue to explore such kinds of new materials for applications in anticounterfeiting and advanced displays.