Tunable Afterglow and Self-Trapped Exciton Emissions in Zr (IV)-Based Organic-Inorganic Metal Halide Hybrids by Metal-Ion Doping.

Low-dimensional hybrid metal halide (LDHMH) materials have attracted considerable attention owing to their intriguing optical properties. To the best of the knowledge, this is the first study to successfully demonstrate both self-trap exciton (STE) and afterglow emissions in Zr-based LDHMH materials. The obtained pure (Ph3 S)2 ZrCl6 crystals showed near-ultraviolet phosphorescence and a green afterglow owing to the organic cation Ph3 S+ , while the Bi-doped and Sb-doped crystals exhibited both STE and afterglow emissions. However, the Te-doped crystals showed only a broad yellow STE emission owing to the [TeCl6 ]2- octahedron. In addition, all the crystals showed good stability. Notably, Sb-doped crystals produced white light, which can be adjusted between cold white and warm white using different excitations. Finally, this strategy for both STE and afterglow emissions can be applied to other LDHMH materials for optical applications.

Multimodal Luminescent Low-Dimension Cs2ZrCl6:xSb3+ Crystals for White Light-Emitting Diodes and Information Encryption.

Low-dimension perovskite materials have attracted wide attention due to their excellent optical properties and stability. Herein, Sb3+-doped Cs2ZrCl6 crystals are synthesized by a coprecipitation method in which Sb3+ ions partially replace Zr4+ ions. The Cs2ZrCl6:xSb3+ powder shows blue and orange-red emissions under a 254 and 365 nm light, respectively, due to the [ZrCl6]2- octahedron and [SbCl6]3- octahedron. The photoluminescence quantum yield (PLQY) of Cs2ZrCl6:xSb3+ (x = 0.1) crystals is up to 52.5%. According to experimental and computational results, the emission mechanism of the Cs2ZrCl6:xSb3+ crystals is proposed. On the one hand, a wide blue emission with a large Stokes shift is caused by the self-trapping excitons of [ZrCl6]2- octahedra under a 260 nm excitation. On the other hand, the luminescence mechanism of [SbCl6]3- octahedron is divided into two parts: 1P1 → 1S0 (490 nm) and 3P1 → 1S0 (625 nm). The broad-band emission, high PLQY, and excellent stability endow the Cs2ZrCl6:xSb3+ powders with the potential for the fabrication of white light-emitting diodes (WLEDs). A WLED device is fabricated using a commercial 310 nm NUV chip, which shows a high color rendering index of 89.7 and a correlated color temperature of 5333 K. In addition, the synthesized Cs2ZrCl6:xSb3+ crystals can be also successfully used for information encryption. Our work will provide a deep understanding of the photophysical properties of Sb3+-doped perovskites and facilitate the development of Cs2ZrCl6:xSb3+ crystals in encrypting multilevel optical codes and WLEDs.

Fast HCl-free Synthesis of Lead-free Rb2ZrCl6:xSb3+ Perovskites.

Due to the toxicity and instability issues of lead halide perovskites, lead-free perovskites have recently emerged as a viable alternative. However, significant optical band gaps of lead-free perovskites exert influence on their luminescent properties. Fortunately, the addition of dopants becomes an efficacious solution. The current widely utilized methods for synthesizing perovskites almost require high temperatures, a long period, and atmosphere protection, which cost more energy and resources. In this paper, we report that Rb2ZrCl6:xSb3+ perovskite phosphors can be easily prepared by a wet grinding approach at room temperature, which is a more efficient and facile process. Due to the self-trapped excitons of the host structure and Sb3+ ions, the produced samples display blue-white and orange fluorescence under UV lamp irradiation at 254 and 365 nm, respectively. In the photoluminescence spectrum, the doped perovskite exhibits an emission peak at 630 nm under excitation at 365 nm. Importantly, the prepared phosphors have tunable emissions related to the excitation wavelength. In addition, our produced powders show remarkable stability at room temperature, laying the foundations for this approach to be widely used in perovskite production.

Targeted high-precision up-converting thermometer platform over multiple temperature zones with Er3.

Ratiometric luminescence thermometry based on trivalent erbium ions is a noninvasive remote sensing technique with high spatial and temporal resolution. The thermal coupling between two adjacent energy levels follows the Boltzmann statistics, whose effective range is related to the energy gap between the multi-excited states. However, the limitations of different thermally coupled levels (TCLs) in Er-based thermometers are rarely mentioned. Here, a type of targeted high-precision luminescence thermometer was designed using a lead-free double perovskite platform by selecting multiple TCLs of the Er3+ ion. According to the selection of different TCLs in a single system platform, more precise temperature resolution can be obtained in different temperature regions from 100 K to almost 880 K. This work provides a quantitative guideline that may pave the way for the development of the next generation of temperature sensor based on trivalent erbium ions.

Ultra-High-Sensitive Temperature Sensing Based on Er3+ and Yb3+ Co-Doped Lead-Free Double Perovskite Microcrystals.

Fluorescence intensity ratio (FIR) thermometry, a new contactless temperature measurement, can achieve accurate measurements in a harsh environment. In this work, all-inorganic lead-free Cs2AgInCl6: Er-Yb and Cs2AgBiCl6: Er-Yb microcrystals emit bright green up-conversion emission, which are synthesized by precipitation at a low temperature (80 °C). In up-conversion emission, FIR of the 2H11/2 → 4I15/2 band to the 4S3/2 → 4I15/2 band exhibits temperature dependence, which can be used as the temperature measurement parameter, so-called FIR thermometry. Moreover, the theoretically accurate measurement range is from 100 to 600 K, achieving maximum absolute sensitivities from 0.0130 to 0.0113 K-1, respectively. The principle of up-conversion and high sensitivity is well explained by calculating the partial density of states. Compared to the reported thermometry materials based on the FIR method, the prepared all-inorganic lead-free Cs2AgInCl6: Er-Yb and Cs2AgBiCl6: Er-Yb microcrystals show outstanding temperature measurement width and sensitivity, becoming a potential candidate for high-sensitivity optical temperature sensors.