Wet chemistry methods,including hot-injection and precipitation methods,have emerged as major synthetic routes for high-quality perovskite nanocrystals in backlit display and scintillation applications.However,low che...Wet chemistry methods,including hot-injection and precipitation methods,have emerged as major synthetic routes for high-quality perovskite nanocrystals in backlit display and scintillation applications.However,low chemical yield hinders their upscale production for practical use.Meanwhile,the labile nature of halide-based perovskite poses a major challenge for long-term storage of perovskite nanocrystals.Herein,we report a green synthesis at room temperature for gram-scale production of CsPbBr3 nanosheets with minimum use of solvent,saving over 95% of the solvent for the unity mass nanocrystal production.The perovskite colloid exhibits record stability upon long-term storage for up to 8 months,preserving a photoluminescence quantum yield of 63% in solid state.Importantly,the colloidal nanosheets show self-assembly behavior upon slow solidification,generating a crack-free thin film in a large area.The uniform film was then demonstrated as an efficient scintillation screen for X-ray imaging.Our findings bring a scalable tool for synthesis of high-quality perovskite nanocrystals,which may inspire the industrial optoelectronic application of large-area perovskite film.展开更多
Graphene-based surface plasmon waveguides(SPWs) show high confinement well beyond the diffraction limit at terahertz frequencies. By combining a graphene SPW and nonlinear material, we propose a novel graphene/AlGaAs ...Graphene-based surface plasmon waveguides(SPWs) show high confinement well beyond the diffraction limit at terahertz frequencies. By combining a graphene SPW and nonlinear material, we propose a novel graphene/AlGaAs SPW structure for terahertz wave difference frequency generation(DFG) under near-infrared pumps.The composite waveguide, which supports single-mode operation at terahertz frequencies and guides two pumps by a high-index-contrast AlGaAs∕Al Oxstructure, can confine terahertz waves tightly and realize good mode field overlap of three waves. The phase-matching condition is satisfied via artificial birefringence in an AlGaAs∕Al Ox waveguide together with the tunability of graphene, and the phase-matching terahertz wave frequency varies from 4 to 7 THz when the Fermi energy level of graphene changes from 0.848 to 2.456 eV. Based on the coupled-mode theory, we investigate the power-normalized conversion efficiency for the tunable terahertz wave DFG process by using the finite difference method under continuous wave pumps, where the tunable bandwidth can reach 2 THz with considerable conversion efficiency. To exploit the high peak powers of pulses, we also discuss optical pulse evolutions for pulse-pumped terahertz wave DFG processes.展开更多
基金supported by National Natural Science Foundation of China (Nos. 21805111 and 11405073)Taishan Scholar Fund
文摘Wet chemistry methods,including hot-injection and precipitation methods,have emerged as major synthetic routes for high-quality perovskite nanocrystals in backlit display and scintillation applications.However,low chemical yield hinders their upscale production for practical use.Meanwhile,the labile nature of halide-based perovskite poses a major challenge for long-term storage of perovskite nanocrystals.Herein,we report a green synthesis at room temperature for gram-scale production of CsPbBr3 nanosheets with minimum use of solvent,saving over 95% of the solvent for the unity mass nanocrystal production.The perovskite colloid exhibits record stability upon long-term storage for up to 8 months,preserving a photoluminescence quantum yield of 63% in solid state.Importantly,the colloidal nanosheets show self-assembly behavior upon slow solidification,generating a crack-free thin film in a large area.The uniform film was then demonstrated as an efficient scintillation screen for X-ray imaging.Our findings bring a scalable tool for synthesis of high-quality perovskite nanocrystals,which may inspire the industrial optoelectronic application of large-area perovskite film.
基金National Natural Science Foundation of China(NSFC)(11547187,11405073,61405073)Shandong Provincial Key R&D Program(2017CXGC0416)
文摘Graphene-based surface plasmon waveguides(SPWs) show high confinement well beyond the diffraction limit at terahertz frequencies. By combining a graphene SPW and nonlinear material, we propose a novel graphene/AlGaAs SPW structure for terahertz wave difference frequency generation(DFG) under near-infrared pumps.The composite waveguide, which supports single-mode operation at terahertz frequencies and guides two pumps by a high-index-contrast AlGaAs∕Al Oxstructure, can confine terahertz waves tightly and realize good mode field overlap of three waves. The phase-matching condition is satisfied via artificial birefringence in an AlGaAs∕Al Ox waveguide together with the tunability of graphene, and the phase-matching terahertz wave frequency varies from 4 to 7 THz when the Fermi energy level of graphene changes from 0.848 to 2.456 eV. Based on the coupled-mode theory, we investigate the power-normalized conversion efficiency for the tunable terahertz wave DFG process by using the finite difference method under continuous wave pumps, where the tunable bandwidth can reach 2 THz with considerable conversion efficiency. To exploit the high peak powers of pulses, we also discuss optical pulse evolutions for pulse-pumped terahertz wave DFG processes.
