The Experts below are selected from a list of 34068 Experts worldwide ranked by ideXlab platform

Min Xiao - One of the best experts on this subject based on the ideXlab platform.

  • Phase Segregation due to ion migration in all inorganic mixed halide perovskite nanocrystals
    Nature Communications, 2019
    Co-Authors: Huichao Zhang, Ying Tang, Hua Wang, Chunfeng Zhang, Xiaoyong Wang, Yu Zhang, Min Xiao
    Abstract:

    Semiconductor mixed-halide perovskites featured with a tunable energy bandgap are ideal candidates for light absorbers in tandem solar cells as well as fluorescent materials in light-emitting diodes and nanoscale lasers. These device advancements are currently hindered by the light-induced Phase Segregation effect, whereby ion migration would yield smaller-bandgap domains with red-shifted photoluminescence. Here we show that upon laser excitation all-inorganic mixed-halide nanocrystals unexpectedly exhibit a blue shift in the photoluminescence peak that can revert back in the dark, thus depicting the processes of ion migration out of and back to the originally excited nanocrystals. Interestingly, this reversible photoluminescence shift can also be induced by electrical biasing of mixed-halide nanocrystals without the injection of charge carriers. The above findings suggest that it is the local electric field that breaks the ionic bonds in mixed-halide nanocrystals, which could be a universal origin for light-induced Phase Segregation observed in other mixed-halide perovskite materials.

Shixun Lian - One of the best experts on this subject based on the ideXlab platform.

  • discovery of blue emitting eu2 activated sodium aluminate phosphor with high thermal stability via Phase Segregation
    Chemical Engineering Journal, 2020
    Co-Authors: Xujian Zhang, Jilin Zhang, Yongfu Liu, Shixun Lian
    Abstract:

    Abstract Thermally stable phosphors are crucial for the application in phosphor-converted white light-emitting diodes. This paper reports the evolution of Phase compositions in nominal Na2−xAl2B2O7:xEu (x = 0.02–2.0) upon replacing Na atoms by Eu atoms. Eu2+-activated blue-emitting phosphor was discovered through Phase Segregation combined with related analyses. The structure, Phase composition and related luminescent properties were investigated by X-ray powder diffraction, backscattered electron image combined with elemental mapping, cathodoluminescence-combined scanning electron microscope, and temperature-dependent emission spectra, etc. Analyses results suggest that EuBO3 Phase segregates upon the gradual replacement of Na by Eu atoms, which is accompanied by Phase transformation from Na2Al2B2O7:Eu2+ to NaAl11O17:Eu2+ and dramatic enhancement of blue emission. The broad emission band is peaking at around 470 nm under UV irradiation. The internal quantum efficiencies of nominal Na0.4Al2B2O7:1.6Eu and Na0.2Al2B2O7:1.8Eu are 58.6% and 60.2%, respectively, which contain both NaAl11O17 and EuBO3 Phase. The emission intensity for these two samples at 150 °C remains 96% (x = 1.6) and 83% (x = 1.8) of the room-temperature values, respectively.

Kento Okoshi - One of the best experts on this subject based on the ideXlab platform.

  • smectic smectic Phase Segregation occurring in binary mixtures of long and short rigid rod helical polysilanes
    Macromolecules, 2019
    Co-Authors: Itsuki Kato, Katsuhiko Sunahara, Kento Okoshi
    Abstract:

    Small-angle X-ray scattering and atomic force microscopy were used to observe smectic–smectic Phase Segregation in binary mixtures of rigid-rod-like helical poly[n-decyl-(S)-2-methylbutylsilane] (PDMS) polymers with molecular-weight ratios of 4.82 and narrow molecular-weight distributions. Phase Segregation is attributed to entropic effects as the homopolymers in the binary mixture differ only in molecular weight. Entropy-driven Segregation in smectic Phases was theoretically predicted in mixtures of rodlike particles with different lengths under high pressure. Binary mixtures of long and short PDMS with broader molecular-weight distributions, which do not form smectic Phases, showed no such Segregation, verifying that the driving force for Segregation is the entropy gained through smectic-Phase formation. The binary mixture of a long PDMS with a narrow molecular-weight distribution and a short PDMS with a broad molecular-weight distribution showed Segregation of each component, indicating that the entrop...

  • Smectic–Smectic Phase Segregation Occurring in Binary Mixtures of Long and Short Rigid-Rod Helical Polysilanes
    2019
    Co-Authors: Itsuki Kato, Katsuhiko Sunahara, Kento Okoshi
    Abstract:

    Small-angle X-ray scattering and atomic force microscopy were used to observe smectic–smectic Phase Segregation in binary mixtures of rigid-rod-like helical poly­[n-decyl-(S)-2-methylbutylsilane] (PDMS) polymers with molecular-weight ratios of 4.82 and narrow molecular-weight distributions. Phase Segregation is attributed to entropic effects as the homopolymers in the binary mixture differ only in molecular weight. Entropy-driven Segregation in smectic Phases was theoretically predicted in mixtures of rodlike particles with different lengths under high pressure. Binary mixtures of long and short PDMS with broader molecular-weight distributions, which do not form smectic Phases, showed no such Segregation, verifying that the driving force for Segregation is the entropy gained through smectic-Phase formation. The binary mixture of a long PDMS with a narrow molecular-weight distribution and a short PDMS with a broad molecular-weight distribution showed Segregation of each component, indicating that the entropy gain of short-polymer-only smectic Phase formation surpasses the loss of mixing entropy

Xujian Zhang - One of the best experts on this subject based on the ideXlab platform.

  • discovery of blue emitting eu2 activated sodium aluminate phosphor with high thermal stability via Phase Segregation
    Chemical Engineering Journal, 2020
    Co-Authors: Xujian Zhang, Jilin Zhang, Yongfu Liu, Shixun Lian
    Abstract:

    Abstract Thermally stable phosphors are crucial for the application in phosphor-converted white light-emitting diodes. This paper reports the evolution of Phase compositions in nominal Na2−xAl2B2O7:xEu (x = 0.02–2.0) upon replacing Na atoms by Eu atoms. Eu2+-activated blue-emitting phosphor was discovered through Phase Segregation combined with related analyses. The structure, Phase composition and related luminescent properties were investigated by X-ray powder diffraction, backscattered electron image combined with elemental mapping, cathodoluminescence-combined scanning electron microscope, and temperature-dependent emission spectra, etc. Analyses results suggest that EuBO3 Phase segregates upon the gradual replacement of Na by Eu atoms, which is accompanied by Phase transformation from Na2Al2B2O7:Eu2+ to NaAl11O17:Eu2+ and dramatic enhancement of blue emission. The broad emission band is peaking at around 470 nm under UV irradiation. The internal quantum efficiencies of nominal Na0.4Al2B2O7:1.6Eu and Na0.2Al2B2O7:1.8Eu are 58.6% and 60.2%, respectively, which contain both NaAl11O17 and EuBO3 Phase. The emission intensity for these two samples at 150 °C remains 96% (x = 1.6) and 83% (x = 1.8) of the room-temperature values, respectively.

Itsuki Kato - One of the best experts on this subject based on the ideXlab platform.

  • smectic smectic Phase Segregation occurring in binary mixtures of long and short rigid rod helical polysilanes
    Macromolecules, 2019
    Co-Authors: Itsuki Kato, Katsuhiko Sunahara, Kento Okoshi
    Abstract:

    Small-angle X-ray scattering and atomic force microscopy were used to observe smectic–smectic Phase Segregation in binary mixtures of rigid-rod-like helical poly[n-decyl-(S)-2-methylbutylsilane] (PDMS) polymers with molecular-weight ratios of 4.82 and narrow molecular-weight distributions. Phase Segregation is attributed to entropic effects as the homopolymers in the binary mixture differ only in molecular weight. Entropy-driven Segregation in smectic Phases was theoretically predicted in mixtures of rodlike particles with different lengths under high pressure. Binary mixtures of long and short PDMS with broader molecular-weight distributions, which do not form smectic Phases, showed no such Segregation, verifying that the driving force for Segregation is the entropy gained through smectic-Phase formation. The binary mixture of a long PDMS with a narrow molecular-weight distribution and a short PDMS with a broad molecular-weight distribution showed Segregation of each component, indicating that the entrop...

  • Smectic–Smectic Phase Segregation Occurring in Binary Mixtures of Long and Short Rigid-Rod Helical Polysilanes
    2019
    Co-Authors: Itsuki Kato, Katsuhiko Sunahara, Kento Okoshi
    Abstract:

    Small-angle X-ray scattering and atomic force microscopy were used to observe smectic–smectic Phase Segregation in binary mixtures of rigid-rod-like helical poly­[n-decyl-(S)-2-methylbutylsilane] (PDMS) polymers with molecular-weight ratios of 4.82 and narrow molecular-weight distributions. Phase Segregation is attributed to entropic effects as the homopolymers in the binary mixture differ only in molecular weight. Entropy-driven Segregation in smectic Phases was theoretically predicted in mixtures of rodlike particles with different lengths under high pressure. Binary mixtures of long and short PDMS with broader molecular-weight distributions, which do not form smectic Phases, showed no such Segregation, verifying that the driving force for Segregation is the entropy gained through smectic-Phase formation. The binary mixture of a long PDMS with a narrow molecular-weight distribution and a short PDMS with a broad molecular-weight distribution showed Segregation of each component, indicating that the entropy gain of short-polymer-only smectic Phase formation surpasses the loss of mixing entropy