Development of thermally stable red-emitting lead-free double-perovskite phosphors with an internal PLQY approaching 100.

White light-emitting diode (WLEDs), acting as a new generation of solid-state lighting, play a critical role in energy conservation. Red-emitting phosphors with high efficiency could effectively improve the quality of WLED devices. In this report, Eu3+-doped Ca2ScTaO6 luminescent materials have been successfully synthesized by a high-temperature solid-state method. Its crystal structure was confirmed to be a monoclinic lead-free double-perovskite material system with the space group P21/n by the X-ray diffraction patterns. The strongest emission peak was about 614 nm distributed to the 5D0 → 7F2 electric-dipole transition. Additionally, the optimal doping concentration was found to be 40 mol%, and the concentration quenching mechanism is assigned to d-d interactions. The Ca2ScTaO6:Eu3+ phosphors exhibited an ultrahigh internal quantum yield (about 100%) with good thermal stability (81.5% at 423 K compared with the emission intensity at 303 K). Furthermore, a WLED with a suitable correlated color temperature (4201 K) and a color rendering index (87.62) was fabricated. The phosphor-based polydimethylsiloxane light-emitting flexible film exhibited good luminescence, which is suitable to be utilized in flexible displays. The obtained results suggest that the high-efficiency red-emitting Ca2ScTaO6:Eu3+ phosphors are promising commercial candidates for use in near-ultraviolet-excited WLEDs.

Designing dual-emission phosphors for temperature warning indication and dual-mode luminescence thermometry.

Color tunable phosphors of Mn4+ and Tb3+ co-doped double-perovskite SrGdLiTeO6 (SGLT) were synthesized in this work. The crystal parameters and photoluminescence performances were investigated in detail. By taking advantage of the different thermal quenching strengths between Mn4+ and Tb3+ ions, the emission color of SGLT:0.7%Mn4+/1%Tb3+ changed from red to green, which could be used for high-temperature temperature warning indication. Moreover, according to the luminescence intensity ratio (LIR) technique, wide temperature-range optical thermometry was developed and further, the maximum relative sensitivity (SR1) value of the SGLT:0.7%Mn4+/5%Tb3+ phosphor was determined to be 1.49% K-1 at 560 K. On the other hand, the sensing properties were also analyzed based on the temperature-dependent lifetime method. The most interesting thing is that the maximum SR2 value reached 1.88% K-1 at 573 K. This work proved that the Mn4+ and Tb3+ co-doped double-perovskite SrGdLiTeO6 could be potentially used in temperature warning indication and high sensitivity luminescence thermometry.

Deep-red-emitting phosphors of Mn4+-activated tantalite for high-sensitivity lifetime thermometry and security films.

Herein, single monoclinic phase Mn4+-doped Sr2InTaO6 (SITO) phosphors were reported in terms of both luminescence behaviors and potential applications. The optimal Mn4+-doped SITO (0.3 mol%) exhibited a good color purity of 92.9% in a deep-red region with a chromaticity coordinate of (0.707, 0.293). In addition, the local structure of Mn4+ in the SITO matrix was determined. The crystal-field strength was calculated to be approximately 1781.7 cm-1 whereas the nephelauxetic ratio was determined to be 1.04. Furthermore, the flexible SITO:Mn4+-YAG:Ce3+ security film was fabricated for use in anti-counterfeiting applications, which could emit different colors under various lighting sources. The SITO:Mn4+ phosphors exhibited a high sensing sensitivity based on the luminescence lifetime. Consequently, the SITO:Mn4+ phosphors can be employed in bifunctional platforms of luminescence lifetime thermometry and anti-counterfeiting applications.

Designing bifunctional platforms for LED devices and luminescence lifetime thermometers: a case of non-rare-earth Mn4+ doped tantalate phosphors.

Non-rare-earth Mn4+ doped tantalate (Sr2GdTaO6) phosphors exhibiting deep-red emission were synthesized. Afterward, the phase structure, morphology, and optical properties (e.g., emission spectra, concentration quenching, decay curves, thermal stability, quantum yields, etc.) were systematically investigated. Under the optimal conditions, the Sr2GdTaO6:0.005Mn4+ phosphor showed an excellent color purity of 96.41% while the chromaticity coordinates were (0.721, 0.279). Besides, the optimal sample exhibited good thermal stability, and, hence, it can be packaged into light-emitting diode (LED) devices. Red-emitting LED devices could show strong far-red emission and could be suggested for plant cultivation lighting. On the other hand, white-emitting LED devices could find use in indoor illumination. Moreover, with the aid of temperature-dependent lifetime (TDL), a good relative sensing sensitivity (1.73% K-1 at 453 K) of the luminescent thermometer was established. Herein, all the above findings suggested that Sr2GdTaO6:Mn4+ phosphors are a potential candidate for bifunctional platforms of solid-state lighting and luminescence lifetime thermometers.

Regulating Dendrite-Free Zinc Deposition by Red Phosphorous-Derived Artificial Protective Layer for Zinc Metal Batteries.

Rational architecture design of the artificial protective layer on the zinc (Zn) anode surface is a promising strategy to achieve uniform Zn deposition and inhibit the uncontrolled growth of Zn dendrites. Herein, a red phosphorous-derived artificial protective layer combined with a conductive N-doped carbon framework is designed to achieve dendrite-free Zn deposition. The Zn-phosphorus (ZnP) solid solution alloy artificial protective layer is formed during Zn plating. Meanwhile, the dynamic evolution mechanism of the ZnP on the Zn anode is successfully revealed. The concentration gradient of the electrolyte on the electrode surface can be redistributed by this protective layer, thereby achieving a uniform Zn-ion flux. The fabricated Zn symmetrical battery delivers a dendrite-free plating/stripping for 1100 h at the current density of 2.0 mA cm-2 . Furthermore, aqueous Zn//MnO2 full cell exhibits a reversible capacity of 200 mAh g-1 after 350 cycles at 1.0 A g-1 . This study suggests an effective solution for the suppression of Zn dendrites in Zn metal batteries, which is expected to provide a deep insight into the design of high-performance rechargeable aqueous Zn-ion batteries.

Recent Advanced Development of Artificial Interphase Engineering for Stable Sodium Metal Anodes.

A solid electrolyte interphase (SEI) on a sodium (Na) metal anode strongly affects the Na deposition morphology and the cycle life of Na metal batteries (SMBs). SMB applications are hindered by an unstable SEI and dendrite growth on the Na anode surface, which directly cause low coulombic efficiency and can even lead to safety issues. An artificial interface layer can stabilize Na metal anodes, be easily tailored, and is barely affected by electrochemical processes. In this review, recent advances that support the stability of working Na metal anodes are focused via artificial interphase engineering of inorganic materials, organic materials, and organic-inorganic composite materials, with an emphasis on the significance of interface engineering in SMBs. Fundamental investigations of artificial interphase engineering are also discussed on Na metal anodes and some recent research is summarized to enhance the interface between Na metal and electrolytes using an artificial interface layer. The prospects for interphase chemistry for Na metal anodes are provided to open a way to safe, high-energy, next-generation SMBs.

Room-temperature synthesis of near-ultraviolet light-excited Tb3+-doped NaBiF4 green-emitting nanoparticles for solid-state lighting.

We reported a facile reaction technique to prepare Tb3+-doped NaBiF4 green-emitting nanoparticles at room temperature. Under 378 nm excitation, the prepared samples exhibited the featured emissions of Tb3+ ions and the green emission located at 543 nm corresponding to the 5D0 → 7F4 transition was observed in the photoluminescence (PL) emission spectra. The PL emission intensity relied on the dopant concentration and its optimum value was determined to be 50 mol%. The involved concentration quenching mechanism was dominated by the electric dipole-dipole interaction and the critical distance was evaluated to be around 10.4 Å. Meanwhile, the color coordinate and color purity of the obtained emission were revealed to be (0.328, 0.580) and 62.4%, respectively. The thermal quenching performance of the synthesized nanoparticles was analyzed using the temperature-dependent PL emission spectra and the activation energy was calculated to be 0.39 eV. By integrating a near-ultraviolet chip with the prepared nanoparticles, a dazzling green light-emitting diode was fabricated to explore the feasibility of the Tb3+-doped NaBiF4 nanoparticles for solid-state lighting applications.