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Materials|94 Article(s)
Room-temperature synthesis of cyan CsPb(Cl/Br)3/SiO2 nanospheres with LiCl-H2O solution
Peiyuan Cao, Bobo Yang, Yanrong Cao, Fei Zheng, and Jun Zou
There are many strategies to maintain the excellent photoluminescence (PL) characteristics of perovskite quantum dots (QDs). Here, we proposed a facile and effective method to prepare cyan CsPb(Cl/Br)3/SiO2 nanospheres at room temperature. Cubic CsPb(Cl/Br)3 was obtained by adding a LiCl-H2O solution and anion exchange reaction. With (3-aminopropyl)triethoxysilane as an auxiliary agent, a QDs/SiO2 composite was extracted from a sol-gel solution by precipitate-encapsulation method. The transmission electron microscopy images and Fourier transform infrared spectra indicated the QDs were indeed embedded in silica substances. Besides, humidity stability and thermal stability show the composite possesses a great application value. Finally, cyan QDs@SiO2 powder has a high PL quantum yield of up to 84%; the stable cyan fluorescent powder does have great potential to play a key role in commercial full spectrum display. There are many strategies to maintain the excellent photoluminescence (PL) characteristics of perovskite quantum dots (QDs). Here, we proposed a facile and effective method to prepare cyan CsPb(Cl/Br)3/SiO2 nanospheres at room temperature. Cubic CsPb(Cl/Br)3 was obtained by adding a LiCl-H2O solution and anion exchange reaction. With (3-aminopropyl)triethoxysilane as an auxiliary agent, a QDs/SiO2 composite was extracted from a sol-gel solution by precipitate-encapsulation method. The transmission electron microscopy images and Fourier transform infrared spectra indicated the QDs were indeed embedded in silica substances. Besides, humidity stability and thermal stability show the composite possesses a great application value. Finally, cyan QDs@SiO2 powder has a high PL quantum yield of up to 84%; the stable cyan fluorescent powder does have great potential to play a key role in commercial full spectrum display.
Chinese Optics Letters
- Publication Date: Jul. 10, 2020
- Vol. 18, Issue 7, 071601 (2020)
Blue–green color-tunable emissions in novel transparent Sr2LuF7:Eu/Tb glass-ceramics for WLEDs
Xiaoman Li, Shaoshuai Zhou, Rongfei Wei, Xueyun Liu, Bingqiang Cao, and Hai Guo
To introduce ordered nano-structures inside a transparent amorphous matrix with superior optical and mechanical properties bears scientific and technological importance, yet limited success has been achieved. Here, via simple melting-quenching and subsequent thermal activation, we report the successful preparation of transparent nano-structured glass-ceramics embedded in Sr2LuF7 nano-crystals (～26 nm), as evidenced by X-ray diffraction, transmission electron microscopy (TEM), and high resolution TEM. The successful incorporation of dopants into formed Sr2LuF7 nano-crystals with low phonon energy results in highly tunable blue–green photoemission, which depends on excitation wavelength, dopant type, and temperature. We found that Eu3+ and Eu2+ ions co-exist in this hybrid optical material, accompanied by the broadband blue emission of Eu2+ and sharp red emissions of Eu3+. A series of optical characterizations are summoned, including emission/excitation spectrum and decay curve measurement, to reveal the reduction mechanism of Eu3+ to Eu2+. Furthermore, near green–white photoemission is achieved via the enrichment of Tb3+/Eu3+ into crystallized Sr2LuF7 nano-crystals. The temperature-dependent visible photoemission reveals thermal activation energy increases with the precipitation of Sr2LuF7 nano-crystals in a glass matrix, suggesting better thermal stability of glass-ceramics than precursor glasses. These results could not only deepen the understanding of glass-ceramics but also indicate the promising potential of Eu3+/Tb3+-ions-doped Sr2LuF7 glass-ceramics for UV pumped white light emitting diodes (WLEDs) with good thermal stability. To introduce ordered nano-structures inside a transparent amorphous matrix with superior optical and mechanical properties bears scientific and technological importance, yet limited success has been achieved. Here, via simple melting-quenching and subsequent thermal activation, we report the successful preparation of transparent nano-structured glass-ceramics embedded in Sr2LuF7 nano-crystals (～26 nm), as evidenced by X-ray diffraction, transmission electron microscopy (TEM), and high resolution TEM. The successful incorporation of dopants into formed Sr2LuF7 nano-crystals with low phonon energy results in highly tunable blue–green photoemission, which depends on excitation wavelength, dopant type, and temperature. We found that Eu3+ and Eu2+ ions co-exist in this hybrid optical material, accompanied by the broadband blue emission of Eu2+ and sharp red emissions of Eu3+. A series of optical characterizations are summoned, including emission/excitation spectrum and decay curve measurement, to reveal the reduction mechanism of Eu3+ to Eu2+. Furthermore, near green–white photoemission is achieved via the enrichment of Tb3+/Eu3+ into crystallized Sr2LuF7 nano-crystals. The temperature-dependent visible photoemission reveals thermal activation energy increases with the precipitation of Sr2LuF7 nano-crystals in a glass matrix, suggesting better thermal stability of glass-ceramics than precursor glasses. These results could not only deepen the understanding of glass-ceramics but also indicate the promising potential of Eu3+/Tb3+-ions-doped Sr2LuF7 glass-ceramics for UV pumped white light emitting diodes (WLEDs) with good thermal stability.
Chinese Optics Letters
- Publication Date: May. 10, 2020
- Vol. 18, Issue 5, 051601 (2020)
Efficient up-conversion Yb3+, Er3+ co-doped Na5Lu9F32 single crystal for photovoltaic application under solar cell spectrum excitation
Xiong Zhou, Hui Wang, Haiping Xia, Hongwei Song, Xu Chen, Jianxu Hu, and Baojiu Chen
Yb3+/Er3+ co-doped Na5Lu9F32 single crystals used as a spectral up-converter to improve the power conversion efficiency of perovskite solar cells are prepared via an improved Bridgman approach. Green and red up-conversion (UC) emissions under the excitation of near-infrared (NIR) bands of 900–1000 nm and 1400–1600 nm can be observed. The effectiveness of the prepared materials as a spectral converter is verified by the enhancement of power conversion efficiency of perovskite solar cells. The sample with a UC layer is 15.5% more efficient in converting sunlight to electricity compared to the UC layer-free sample due to the absorption of sunlight in the NIR range. The results suggest the synthesized Yb3+/Er3+ co-doped Na5Lu9F32 single crystals are suitable for enhancing the performance of perovskite solar cells. Yb3+/Er3+ co-doped Na5Lu9F32 single crystals used as a spectral up-converter to improve the power conversion efficiency of perovskite solar cells are prepared via an improved Bridgman approach. Green and red up-conversion (UC) emissions under the excitation of near-infrared (NIR) bands of 900–1000 nm and 1400–1600 nm can be observed. The effectiveness of the prepared materials as a spectral converter is verified by the enhancement of power conversion efficiency of perovskite solar cells. The sample with a UC layer is 15.5% more efficient in converting sunlight to electricity compared to the UC layer-free sample due to the absorption of sunlight in the NIR range. The results suggest the synthesized Yb3+/Er3+ co-doped Na5Lu9F32 single crystals are suitable for enhancing the performance of perovskite solar cells.
Chinese Optics Letters
- Publication Date: Sep. 10, 2019
- Vol. 17, Issue 9, 091601 (2019)
Comparative study of coherent terahertz emission from Fe/Pt ferromagnetic heterostructures
Xiao-Peng He, Pan-Hui Huang, Xiao-Yu Yang, Zuan-Ming Jin, Shi-Tao Lou, Xiao-Lei Zhang, and Qing-Yuan Jin
The ultrafast spin dynamic of in-plane magnetized Fe/Pt films was investigated by terahertz emission spectroscopy. The amplitude of the emitted terahertz wave is proportional to the intensity of the exciting laser beams. Both the amplitude and polarity of the terahertz wave can be adjusted by modifying the external magnetic field. The dependency of the amplitude on external magnetic fields is coincident to the hysteresis loops of the sample. Also, the polarity of the terahertz wave is reversed, as the magnetization orientation is reversed. The super-diffusive transient spin current with an inverse spin Hall effect is attributed to the main mechanism of the terahertz emission. The ultrafast spin dynamic of in-plane magnetized Fe/Pt films was investigated by terahertz emission spectroscopy. The amplitude of the emitted terahertz wave is proportional to the intensity of the exciting laser beams. Both the amplitude and polarity of the terahertz wave can be adjusted by modifying the external magnetic field. The dependency of the amplitude on external magnetic fields is coincident to the hysteresis loops of the sample. Also, the polarity of the terahertz wave is reversed, as the magnetization orientation is reversed. The super-diffusive transient spin current with an inverse spin Hall effect is attributed to the main mechanism of the terahertz emission.
Chinese Optics Letters
- Publication Date: Aug. 10, 2019
- Vol. 17, Issue 8, 081601 (2019)
Abnormal elemental redistribution in oxyfluoride glasses induced by high repetition rate femtosecond laser
Shengzhi Sun, Song Ye, Zhenyan Wang, Juan Song, Bin Qian, and Jianrong Qiu
We report on the elemental redistribution behavior in oxyfluoride glasses with a high repetition rate near-infrared femtosecond laser. Elemental analysis by an electro-probe microanalyzer demonstrates that the redistributions of Ca2+ and Yb3+ ions change dramatically with pulse energy, which are quite different compared with previous reported results. Confocal fluorescence spectra of Yb3+ ions demonstrate that the luminescence intensity changes obviously with the elemental redistribution. The mechanism of the observed phenomenon is discussed. This observation may have potential applications in the fabrication of micro-optical devices. We report on the elemental redistribution behavior in oxyfluoride glasses with a high repetition rate near-infrared femtosecond laser. Elemental analysis by an electro-probe microanalyzer demonstrates that the redistributions of Ca2+ and Yb3+ ions change dramatically with pulse energy, which are quite different compared with previous reported results. Confocal fluorescence spectra of Yb3+ ions demonstrate that the luminescence intensity changes obviously with the elemental redistribution. The mechanism of the observed phenomenon is discussed. This observation may have potential applications in the fabrication of micro-optical devices.
Chinese Optics Letters
- Publication Date: Jun. 10, 2019
- Vol. 17, Issue 6, 061601 (2019)
Photoluminescence properties of Ca4La6(SiO4)4(PO4)2O2-based phosphors for wLEDs
Ju Cheng, Jia Zhang, Jian Lu, Xintian Bian, Hongchao Zhang, Zhonghua Shen, Xiaowu Ni, Pengcheng Ma, and Jin Shi
The apatite compound Ca4La6(SiO4)4(PO4)2O2 (CLSPO) was explored as the host material for phosphors used in white light-emitting diodes (wLEDs). The crystal structure of the CLSPO host prepared by the solid-state reaction method was investigated with Rietveld refinement. The rare earth ions (Eu3+/ Tb3+/Ce3+, Tb3+/Tb3+, Mn2+) activated CLSPO phosphors were synthesized, and their photoluminescence properties, quantum yields, as well as thermal stabilities, were studied. Under near-ultraviolet excitations, the Eu3+ and Tb3+-doped CLSPO compounds exhibited red and green emissions with high luminescence efficiencies. Besides, tunable emissions from green to orange were obtained by introducing Mn2+ ions into the Tb3+-doped CLSPO samples. The results showed that the phosphors studied may have potential applications for wLEDs. The apatite compound Ca4La6(SiO4)4(PO4)2O2 (CLSPO) was explored as the host material for phosphors used in white light-emitting diodes (wLEDs). The crystal structure of the CLSPO host prepared by the solid-state reaction method was investigated with Rietveld refinement. The rare earth ions (Eu3+/ Tb3+/Ce3+, Tb3+/Tb3+, Mn2+) activated CLSPO phosphors were synthesized, and their photoluminescence properties, quantum yields, as well as thermal stabilities, were studied. Under near-ultraviolet excitations, the Eu3+ and Tb3+-doped CLSPO compounds exhibited red and green emissions with high luminescence efficiencies. Besides, tunable emissions from green to orange were obtained by introducing Mn2+ ions into the Tb3+-doped CLSPO samples. The results showed that the phosphors studied may have potential applications for wLEDs.
Chinese Optics Letters
- Publication Date: May. 10, 2019
- Vol. 17, Issue 5, 051602 (2019)
Transient optical properties in fused silica measured by time-resolved high-power laser photometer
Zhen Cao, Hongbo He, Guohang Hu, Yuanan Zhao, Liujiang Yang, and Jianda Shao
A time-resolved high-power laser photometer, which measures the real-time variations of transmission, internal reflection, and scattering simultaneously with picosecond time resolution, was developed to investigate the material response sequence during high-power nanosecond laser irradiation in thick fused silica. It was found that the transient transmission decreased sharply, accompanied by an increase in internal reflection at the rising edge of the laser pulse. The transient transmission recovered, while laser damage did not occur, but it did not recover if the scattering increased, indicating the occurrence of laser damage. The reason for the sharp decrease of transmission and the relationship between the transmission drop and laser damage were discussed. A time-resolved high-power laser photometer, which measures the real-time variations of transmission, internal reflection, and scattering simultaneously with picosecond time resolution, was developed to investigate the material response sequence during high-power nanosecond laser irradiation in thick fused silica. It was found that the transient transmission decreased sharply, accompanied by an increase in internal reflection at the rising edge of the laser pulse. The transient transmission recovered, while laser damage did not occur, but it did not recover if the scattering increased, indicating the occurrence of laser damage. The reason for the sharp decrease of transmission and the relationship between the transmission drop and laser damage were discussed.
Chinese Optics Letters
- Publication Date: May. 10, 2019
- Vol. 17, Issue 5, 051601 (2019)
Arbitrary linear THz wave polarization converter with cracked cross meta-surface
Han Sun, Lan Wang, Yaxin Zhang, Shixiong Liang, Jiaguang Han, Feng Lan, Xinlan Zhou, and Ziqiang Yang
This Letter presents a double-layer structure combining a cracked cross meta-surface and grating surface to realize arbitrary incident linear terahertz (THz) wave polarization conversion. The arbitrary incident linear polarization THz wave will be induced with the same resonant modes in the unit cell, which results in polarization conversion insensitive to the linear polarization angle. Moreover, the zigzag-shaped resonant surface current leads to a strong magnetic resonance between the meta-surface and gratings, which enhances the conversion efficiency. The experimental results show that a more than 70% conversion rate can be achieved under arbitrary linear polarization within a wide frequency band. Moreover, around 0.89 THz nearly perfect polarization conversion is realized. This Letter presents a double-layer structure combining a cracked cross meta-surface and grating surface to realize arbitrary incident linear terahertz (THz) wave polarization conversion. The arbitrary incident linear polarization THz wave will be induced with the same resonant modes in the unit cell, which results in polarization conversion insensitive to the linear polarization angle. Moreover, the zigzag-shaped resonant surface current leads to a strong magnetic resonance between the meta-surface and gratings, which enhances the conversion efficiency. The experimental results show that a more than 70% conversion rate can be achieved under arbitrary linear polarization within a wide frequency band. Moreover, around 0.89 THz nearly perfect polarization conversion is realized.
Chinese Optics Letters
- Publication Date: Apr. 10, 2019
- Vol. 17, Issue 4, 041602 (2019)
Fractional density of states and the overall spontaneous emission control ability of a three-dimensional photonic crystal
Menglin Chen, Zhijun Luo, Yanan Liu, and Zongsong Gan
Fractional density of states (FDOS) hinders the accurate measuring of the overall spontaneous emission (SE) control ability of a three-dimensional (3D) photonic crystal (PC) with the current widely used SE decay lifetime measurement systems. Based on analyzing the FDOS property of a 3D PC from theory and simulation, the excitation focal spot position averaged FDOS with a distribution broadening parameter was proposed to accurately reflect the overall SE control ability of the 3D PC. Experimental work was done to confirm that our proposal is effective, which can contribute to comprehensively characterizing the SE control performance of photonic devices with quantified parameters. Fractional density of states (FDOS) hinders the accurate measuring of the overall spontaneous emission (SE) control ability of a three-dimensional (3D) photonic crystal (PC) with the current widely used SE decay lifetime measurement systems. Based on analyzing the FDOS property of a 3D PC from theory and simulation, the excitation focal spot position averaged FDOS with a distribution broadening parameter was proposed to accurately reflect the overall SE control ability of the 3D PC. Experimental work was done to confirm that our proposal is effective, which can contribute to comprehensively characterizing the SE control performance of photonic devices with quantified parameters.
Chinese Optics Letters
- Publication Date: Apr. 10, 2019
- Vol. 17, Issue 4, 041601 (2019)
Effect of 1070 nm laser intensity on parameters of In0.3Ga0.7As solar cell
Guangji Li, Hongchao Zhang, Chengmin Wang, Yunxiang Pan, Jian Lu, and Dayong Zhou
The photoelectric properties of In0.3Ga0.7As solar cells applied in laser wireless power transmission (LWPT) were studied when they were irradiated by 1070 nm continuous wave (CW) laser of various intensities. The influences of laser intensity on solar cell parameters extracted by the pollination algorithm were analyzed quantitatively. Results show that the conversion efficiency of the cell rose to the maximum and then decreased rapidly in the laser intensity range of 50–900 mW/cm2. With higher energy laser irradiation, the rise of ideality factor and reverse saturation current would lead to the degradation of voltage at the maximum power point, which was the main reason for the decrease of conversion efficiency. The results provide the basis for choosing the appropriate input energy in the case of different transmission systems. The photoelectric properties of In0.3Ga0.7As solar cells applied in laser wireless power transmission (LWPT) were studied when they were irradiated by 1070 nm continuous wave (CW) laser of various intensities. The influences of laser intensity on solar cell parameters extracted by the pollination algorithm were analyzed quantitatively. Results show that the conversion efficiency of the cell rose to the maximum and then decreased rapidly in the laser intensity range of 50–900 mW/cm2. With higher energy laser irradiation, the rise of ideality factor and reverse saturation current would lead to the degradation of voltage at the maximum power point, which was the main reason for the decrease of conversion efficiency. The results provide the basis for choosing the appropriate input energy in the case of different transmission systems.
Chinese Optics Letters
- Publication Date: Mar. 10, 2019
- Vol. 17, Issue 3, 031601 (2019)
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