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Optimizing the structure and tuning the optical properties in low-dimensional organic–inorganic halide perovskites are crucial to practical applications for stable solid-state lighting. Herein, we performed high-pressure investigations on one-dimensional (1D) postperovskite (TDMP)PbBr4(TDMP = trans-2,5-dimethylpiperaziniium), and structure and optical properties under pressure are studied. (TDMP)PbBr4exhibits color tunable emission from cool white light to yellow orange as the pressure increases from atmospheric pressure to 20.0 GPa. It was found that high pressure would facilitate trapping the free exciton (free exciton) to form a self-trapped exciton (STE) state due to increased electron–phonon interaction, thus enhancing STE emission in the pressure range of 4.0–7.0 GPa. At above 7.0 GPa, the STE emission is quenched, which is due to the phonon-assisted nonradiative relaxation. Meanwhile, (TDMP)PbBr4displays reversible piezochromism from colorless to yellow under pressure as a result of the compound undergoing a reversible structural transformation. This work provides an insightful perspective on revealing the relationship between structure and optical properties of 1D postperovskites under high pressure.

Integrating multimode optical properties into a single material simultaneously is promising for improving the security level of fluorescent anticounterfeiting. However, there has been a lack of affirmative principles and unambiguous mechanisms that guide the design of such material. Herein, we achieve color-tunable photoluminescence, long-lived persistent emission, thermally stimulated luminescence, and reversible photochromism in a Tb3+-activated Mg4Ga8Ge2O20phosphor by employing the F-like color center as an energy reservoir. It is experimentally revealed that the role of oxygen vacancies in the lattice of Mg4Ga8Ge2O20is assumed as the main trap for the photogenerated electronic carriers, which is the origin of metastable F-like color centers. The formed color centers with the estimated depths of 0.48–0.95 eV could suppress the recombination of electron–hole pairs, thus giving rise to good photochromism and persistent emission properties, while under various modes of stimulation such as thermal attack or photo radiation, a quick recombination of electron holes happens, accounting for the bright thermally stimulated luminescence and the accompanied color bleaching. Finally, we fabricate a flexible phosphor/polymer composite by encapsulating the developed phosphor into a polydimethylsiloxane matrix, and conceptual demonstration of the composite for the high-security fluorescent anticounterfeiting technology, by virtue of multimode optical phenomena as authentication signals.

The sluggish reaction kinetics and poor structure stability of transition metal dichalcogenides (TMDs)-based anodes in potassium-ion batteries (KIBs) usually cause limited rate performance and rapid capacity decay, which seriously impede their application. Herein, we report a vacancy engineering strategy for preparing a class of Te-doped 1T’-ReSe2anchored onto MXene (Te-ReSe2/MXene) as an advanced anode for KIBs with high performance. By taking advantage of the synergistic effects of the defective Te-ReSe2arrays with expanded interlayers and the elastic MXene nanosheets with self-autoadjustable function, the Te-ReSe2/MXene superstructure exhibits boosted K+ion storage performance, in terms of high reversible capacity (361.1 mA h g−1at 0.1 A g−1over 200 cycles), excellent rate capability (179.3 mA h g−1at 20 A g−1), ultra-long cycle life (202.8 mA h g−1at 5 A g−1over 2000 cycles), and steady operation in flexible full battery, presenting one of the best performances among the TMDs-based anodes reported thus far. The kinetics analysis and theoretical calculations further indicate that satisfactory pseudocapacitive property, high electronic conductivity and outstanding K+ion adsorption/diffusion capability corroborate the accelerated reaction kinetics. Especially, structural characterizations clearly elaborate that the Te-ReSe2/MXene undergoes reversible evolutions of an initial insertion process followed by a conversion reaction.

Water has been labeled as a devil in fabrication and stability of perovskite solar cells. The inherent cognition impels researchers to prepare perovskite films in water-controlled conditions. Herein, water is used as a green solvent to prepare CsPbBr3films through a two-step spin-coating method. Due to the high solubility of CsBr but low solubility of PbBr2in water, it provides a possibility to deposit CsBr onto PbBr2from water solution without destroying the film. Here, high-quality CsPbBr3films are fabricated by spin-coating concentrated CsBr/H2O solution onto the PbBr2film followed by annealing. As a result, the solar cells basing on a configuration of FTO/TiO2/CsPbBr3/Carbon exhibit a power conversion efficiency of 6.12%. This work provides a simple and easy way to prepare high-quality CsPbBr3films for efficient solar cells. It makes a solid step toward reducing the solvent toxicity in the fabrication process of perovskite solar cells. It also breaks the forbidden zone for fabricating perovskite films from water and updates the inherent understanding of water in the research study of perovskite solar cells.

Currently, the study of Mn4+-doped oxide red phosphor is a hot research topic to solve the lack of red component in phosphor-converted white-light-emitting diodes (pc-WLEDs). In this Article, we designed Gd3+/Nb5+cation substitution by Bi3+/Mn4+in Ba2GdNbO6with double-perovskite structure based on the radius and coordination of the cations through high-temperature solid-state reaction. The phase purity and microstructure of double-perovskite Ba2GdNbO6:Bi3+,Mn4+phosphors were characterized by X-ray diffraction and scanning electron microscopy examination. The crystal structures were also determined by the Rietveld refinement, and the photoluminescence (PL) properties were systematically studied. Bi3+and Mn4+ions can be effectively doped in the Ba2GdNbO6matrix with an optical band gap of 3.94 eV. Upon 315 nm UV excitation, the Ba2GdNbO6:Bi3+,Mn4+phosphor shows two emission bands at 464 nm from Bi3+and 689 nm from Mn4+, respectively. By the design of Bi3+→ Mn4+energy transfer, systematic luminescence tuning from blue to red could be achieved because of spectral overlap between the emission spectrum of Bi3+and the excitation spectrum of Mn4+. The corresponding mechanism of the Bi3+→ Mn4+energy-transfer process was investigated in detail by the fluorescence decays and PL spectra. The red emission intensity of Mn4+has been greatly improved by Bi3+→ Mn4+energy transfer. Moreover, the phonon vibration and zero phonon line of Mn4+were studied through temperature-dependent PL. Finally, a WLED was fabricated using a 460 nm blue chip with a yellow YAG:Ce3+phosphor and a red Ba2GdNbO6:0.01Bi3+,0.01Mn4+phosphor, which has a low correlated color temperature (3550 K) and a high color rendering index (89.6). The above results imply that the improved red emission phosphors have a potential application in warm pc-WLED lighting.

High-pressure behaviors of ammonium perchlorate (NH4ClO4), a widely used energetic oxidizer, have been investigated using in situ angle-dispersive X-ray diffraction (XRD) and Raman spectroscopy experiments up to 22.0 and 20.4 GPa, respectively. A sluggish structural transformation is identified, which started at ∼2.4 GPa and completed at ∼10.6 GPa. The crystal structure of high pressure (phase II) is refined to possess a symmetry of P2. The structural transformation is indicated by the obvious changes in XRD patterns, Raman spectra, and discontinuities of peak positions. Variations in lattice constants and volume of unit cell of the ambient structure (phase I) up to ∼10.0 GPa are also presented. The compressibility of phase I is anisotropic. The compression ratio of baxis is larger than that of aand caxes. The bulk modulus of phase I is B0= 24.5(4) GPa, and its first pressure derivative is B0′ = 4.5(2). The phase transition is reversible, as the XRD pattern transformed to the initial profile upon release of pressure. On the basis of the Raman and XRD analysis, the high-pressure-induced phase transition of ammonium perchlorate is proposed to be associated with rearrangement of hydrogen-bonded networks.

The Te-SnS2/MXene superstructure with strong interface interaction and self-autoadjustable function has been successfully demonstrated for the first time to boosting potassium ion storage performance.