Perovskite microcrystals have attracted wide attention and have been applied in extensive optical applications. The CsPbX3 perovskite poses a great threat to the environment due to the presence of lead (Pb), and there is an urgent need to improve the photoluminescence quantum yield. Therefore, a lead-free perovskite microcrystal material Cs2RbxAg1-xIn0.875Bi0.125Cl6 with a high photoluminescence quantum yield (PLQY) was synthesized by a convenient hydrothermal method, with comprehensive characterization of both the structure and optical performance at varying Rb ratios. Optimal properties were observed at x = 0.15 with bright white emission and a PLQY of 32.15%. Superior stability of the novel material in ethanol was observed under the radiation of an excitation light of 365 nm. Interestingly, a blue shift of the emission peak occurred after exposure to humid air, possibly due to the reconstruction of the crystal structure. Moreover, a LED device packaged with this novel material was developed with a desirable color temperature of 3190 K, promising for further lighting applications.
Abstract Glass, with its unique amorphous properties, offers low thermal conductivity, high catalytic activity, insensitivity to interfacial lattice mismatch, and the absence of grain boundaries. Melt‐quenched organic–inorganic hybrid glass has recently gained significant attention as an emerging material because of its excellent processability and formability. Here, an SbCl 3 (C 25 H 46 ClN) x halide with a low melting point (90 °C) and significant formability is reported. Both the crystalline and glass states of SbCl 3 (C 25 H 46 ClN) x have double broadband emission, and the glass state exhibits negative thermal quenching, which is rare in metal halides. Interestingly, the luminescence properties of SbCl 3 (C 25 H 46 ClN) x glass with different x values differ. This feature is utilized to design multimodal anti‐counterfeiting and information encryption applications. Additionally, The inherent melt processing capability of SbCl 3 (C 25 H 46 ClN) x allows it to be shaped into various forms suitable for practical applications. SbCl 3 (C 25 H 46 ClN) x scintillator screens (diameter 2.2 cm) are successfully prepared by low‐temperature melting, achieving an X‐ray imaging resolution of 18 line pairs per millimeter (18 lp mm −1 ). This study demonstrates the potential of melt‐processed organic–inorganic hybrid glass SbCl 3 (C 25 H 46 ClN) x in anti‐counterfeiting, information encryption, and X‐ray detection.
The structure of novel LiAlO2 crystal with Ti concentration of 0.2 at% was studied by measuring the absorption, luminescence and IR spectra. It was found that the crystal has the 196nm typical quarivalent Ti absorption peak, and also the 384nm typical quarivalent Ti emission peak when excited by 235nm light. A color-center model successfully explains the four small peaks in the range of 660—820nm, which disappeared when the samples were annealed in air or Li-rich atmosphere. Compared to the pure LiAlO2, we can find that the intensity and situation of ［LiO4］ are unchanged. Combined with the ICP results, we can count the number of Li vacancies to be about 5.5×1020 for the Ti: LiAlO2 with dimensions of 50mm×1mm.
Optical properties for ZnO thin films grown on (100) ?-LiAlO2 (LAO) substrate by pulsed laser deposition method were investigated. The c-axis oriented ZnO films were grown on (100) ?-LiAlO2 substrates at the substrate temperature of 550 Celsius degrees. The transmittance of the films was over 85%. Peaks attributed to excitons were shown in absorption spectra, which indicated that thin films had high crystallinity. Photoluminescence spectra with the maximum peak at 540 nm were observed at room temperature, which seemed to be ascribed to oxygen vacancy in the ZnO films caused by diffusion of Li from the substrates into the films during the deposition.
A high‐power white laser source is prepared by using a 455 nm blue laser to excite YAG:Ce ceramics. To achieve high‐power output, a water‐cooling device is used to reduce the operating temperature of ceramics. The luminescence properties of laser‐excited phosphor ceramics are studied under different blue excitation power and different irradiation time. The experimental results show that the luminous flux of phosphor ceramics excited by the blue laser increases linearly with the increase of blue laser power, depending on the heat dissipation of the water‐cooling device. When the blue laser power increases to 73.1 W, the phosphor ceramics do not reach the luminescence saturation state. The luminous flux of phosphor ceramics excited by 73.1 W blue laser is stable within 60 min. The maximum luminous flux is 8094 lm, and the maximum working temperature of the ceramics is 110 °C. The experimental results show that water‐cooling packages are an effective means to realize high‐power white laser sources.
This paper investigates the effect of solders with different grain sizes (5–15 μ m, 2–15 μ m, 2–11 μ m) on the mechanical and thermal reliability of flip-chip LED chip Au/Sn Ag Cu/Cu solder joints during reflow soldering. The lead-free solder SAC305 was selected as the solder. The microstructure of the IMC interface and the inferred surface of the solder joint is observed, and the microstructure evolution of the solder joint is analyzed. The void ratio of the solder joints under different grain sizes is tested to characterize the influence of the contact area between the chip and the solder joints on the shear stress. In addition, the solder joints were aged for 1000 h under a relative humidity of 85 °C/85%. The photoelectric thermal performance of the FC-LED filament and the influence of high temperature and high humidity aging on the reliability of the filament were tested and analyzed. The results show that when the size of the solder paste is small and the uniformity is poor within a certain range of solder size, the voids in the flux layer are large and concentrated, and the void ratio is significantly higher, which leads to a decrease in the mechanical reliability of the solder joints. The thermal resistance test results show that the cavity will cause excessive thermal resistance, poor heat dissipation, a significant increase in junction temperature, and a decrease in thermal reliability, which in turn leads to severe light aging and ultimately changes in photoelectric performance. When the grain size is 5–15 μ m, the uniformity of the particle size is good. After the filament is aged for 1000 h at high temperature and humidity, the light maintenance rate remains at 65.6%, and the filament performance is stable and reliable. It has certain reference value in the actual production process.
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