Search

Rare earth ions doped all-inorganic lead halide perovskite quantum dots (PeQDs) have attracted extensive attention due to the rare earth ions doping greatly expanding the optical properties of PeQDs. Here, Er3+ and Yb3+ ions co-doped CsPbCl 3 PeQDs are synthesized by the improved hot-injection method. The excitonic emission and near-infrared (NIR) IIb emission of Er3+ ions and quantum-cutting emission of Yb3+ ions were observed in CsPbCl 3 :Yb3+, Er3+ PeQDs. Interestingly, the NIR IIb emission of Er3+ ions is only obtained in PeQDs through the effective sensitization of Yb3+ ions. The energy transfer efficiency from Yb3+ to Er3+ ions is 23.5%. Furthermore, the optimal photoluminescence quantum yield (PLQY) of a NIR IIb emission for Er3+ ions was got by typical anion exchange reaction, and the value is up to 14.6%. This work provides a new way that further extends the emission wavelength of PeQDs to NIR IIb region, which will broaden the application scope of PeQDs. Image 1 • Er3+ and Yb3+ ions doped CsPbCl 3 PeQDs are synthesized by the improved hot-injection method. • The NIR Ⅱb emission from 1500 to 1700 nm of Er3+ ions doping into CsPbCl 3 PeQDs was got. • This work provides a new way to obtain the NIR IIb emission of PeQDs, which will broaden the application scope of PeQDs. [ABSTRACT FROM AUTHOR]

High-efficiency quantum cutting materials have great application prospects in improving the photoelectric conversion efficiency of silicon-based photoelectric devices. Herein, La3+ and Yb3+ ions co-doped CsPbCl 3 perovskite quantum dots (PQDs) were prepared successfully via the modified hot-injection method. La3+ and Yb3+ ions codoping makes the PLQY of CsPbCl 3 PQDs increase from 5% to 168%. This is because Yb3+ ions doping makes the effective quantum cutting process happen, as well as La3+ ions doping effectively reduces non-radiative transition in CsPbCl 3 PQDs and further improves the quantum cutting efficiency. Finally, La3+ and Yb3+ ions co-doped CsPbCl 3 PQDs film were integrated on silicon-based photodetectors. The spectral range of silicon-based photodetectors is extended to the ultraviolet (UV) region (200–400 nm) besides the visible spectral region. The external quantum efficiency (EQE) is around 67%, and the responsivity is 0.14 A/W, which is comparable to the highest value previously reported. This work provides a new strategy to improve the quantum cutting efficiency and the performance of silicon-based photodetectors. • The PLQY of CsPbCl 3 PQDs increase from 5% to 168% via La3+ and Yb3+ codoping. • La3+/Yb3+ co-doped CsPbCl 3 PQDs were integrated on silicon photodetectors. • The response spanning of silicon photodetectors is extended to the ultraviolet. [ABSTRACT FROM AUTHOR]

Lead-free halide double perovskites are widely used for phosphors converted light emitting diode (pc-LED) devices. However, it remains a challenge to modulate their spectra to meet different application requirements. Herein, Cs 2 NaInCl 6 :Sb3+ double perovskite crystals with excellent blue emission of self-trapped excitons (STEs) were prepared and a lanthanide ions (Ln3+) doping strategy was employed to enable multicolor emissions in this system. The emission colors can be continuously adjusted in a wide range by altering the Ln3+ ions doping levels. Especially, white light emissions with tunable correlated color temperature were obtained in Tb3+, Ho3+ ions codoped samples. Outstanding photoluminescence quantum yields of the samples are ascribed to the sensitization effect of Sb3+ ions and the efficient energy-transfer from STEs to Ln3+ ions. LED devices were further fabricated to demonstrate the great application potentials of the prepared phosphors. These findings provide deep insights for the designing of multicolor double perovskite phosphors. • Sb3+ and different Ln3+ ions were successfully doped in Cs 2 NaInCl 6 by a hydrothermal method. • The emission colors can be continuously adjusted in a wide range by altering the Ln3+ ions doping levels. • Multi-color light-emitting diodes were designed with single component Cs 2 NaInCl 6 phosphors. [ABSTRACT FROM AUTHOR]

Abstract Na 5 Lu 9 F 32 : Yb3+, Tm3+ single crystals prepared by an improved Bridgman method are expected to be incorporated into solar cells as an upconversion layer to expand the absorption range. Upconversion (UC) with weak emission of 488 nm blue, 704 nm red and strong 805 nm near-infrared fluorescence upon 964 nm excitation as well as its pump power dependence on UC emission were obtained in the single crystals. Furthermore, a high external quantum efficiency (EQE) of 2.65% is obtained for Na 5 Lu 9 F 32 : 8%Yb3+, 1%Tm3+ under 1 W/cm2 980 nm excitation. Meanwhile, the temperature-dependent UC emission spectra is studied as a function of temperature in the range of 250–370 K. The cubic dependence of pump power on UC emission reveals that three-photon UC processes are mainly responsible for the 488 nm, 704 nm emissions and the quadratic dependence indicates two-photon process for the 805 nm emission in Tm3+/Yb3+ co-doped Na 5 Lu 9 F 32 single crystals, respectively. The energy transfer processes were studied based on energy level diagram, and the results indicated that the cross-relaxation (CR) between Tm3+ and Tm3+ affect the luminous intensity. Moreover, it can infer that the energy transfer from Tm3+ to Yb3+ exists from the decay curves of Tm3+ at 805 nm under excitation by 964 nm. Highlights • Tm3+/Yb3+ co-doped Na 5 Lu 9 F 32 single crystals were grown successfully first time. • The high emission intensity and long fluorescence lifetime at 805 nm were obtained. • The energy transfer processes upon 964 nm excitation were analysis in depth. [ABSTRACT FROM AUTHOR]

This work aimed at investigating the superiorities of multilayer graphene (MLG) and β-Si 3 N 4 whisker (β-Si 3 N 4w) in synergistically enhancing the toughness of Si 3 N 4 ceramic composites. First, Si 3 N 4 ceramic composites with hybrid 1 wt% MLG and 0 – 5 wt% β-Si 3 N 4w were sintered by spark plasma sintering. Phase constitutions and microstructures of Si 3 N 4 -based ceramic composites were characterized by X-rays diffraction, Raman spectra, and scanning electron microscope. Then, the optimal β-Si 3 N 4w content and sintering process of MLG/β-Si 3 N 4w -toughened Si 3 N 4 ceramic composites were comprehensively optimized by orthogonal experiments. Results indicated that in the case of maintaining the hardness of 15.87 – 18.84 GPa, the fracture toughness of Si 3 N 4 ceramic composites incorporated with 1 wt% MLG and 3 wt% β-Si 3 N 4w was advanced to 11.04 MPa·m1/2, which was 11.29% and 87.12% higher than that of 1 wt% MLG- and 3 wt% β-Si 3 N 4w -reinforced Si 3 N 4 ceramic composites, respectively. Orthogonal experiments demonstrated that 1 wt% MLG/3 wt% β-Si 3 N 4w -toughened Si 3 N 4 ceramic composites sintered at 1600 ℃, 40 MPa, and holding time for 6 min had optimum comprehensive mechanical properties. MLG wrapping and the synergistic effects of pull out, crack deflection, crack branching, and bridging resulted by MLG and β-Si 3 N 4w were the main responsible for the enhancement of toughness. [Display omitted] • MLG/β-Si 3 N 4w synergistic toughened Si 3 N 4 ceramics were sintered by SPS. • Fracture toughness of Si 3 N 4 -based ceramics was enhanced to 11.04 MPa·m1/2. • Optimal contents of MLG and β-Si 3 N 4w were 1 wt% and 3 wt%. • Optimum sintering process were 1600 ℃, 40 MPa, and holding time for 6 min. [ABSTRACT FROM AUTHOR]

Up-conversion is a promising technique for harvesting sub-band-gap photons in photovoltaic devices. The implementation and characterization of rare-earth doped up-converters on a-Si:H solar cells are investigated. Three up-conversion phosphors, β-NaYF 4 :Yb 3+ 20%/Er 3+ 1%, β-NaYF 4 :Yb 3+ 25%/Ho 3+ 1% and β-NaYF 4 :Yb 3+ 60%/Tm 3+ 0.5%, are developed and employed as low energy convert materials for a-Si:H solar cells. Two different ways of adhering the up-converter to the a-Si:H solar cell have been implemented: by dissolving the powder in the polydimethylsiloxane (PDMS) and by compressing it into solid slice with a tablet pressing machine. The performance of a-Si:H solar cells integrating the up-converters is investigated under both 980 nm infrared laser diode and simulated solar light source (AM1.5G) illumination. The Current-Voltage measurements reveal that the β-NaYF 4 :Yb 3+ 20%/Er 3+ 1% up-conversion phosphor performs both up-conversion and scattering functions in improving the overall performance of a-Si:H solar cell. [ABSTRACT FROM AUTHOR]