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  • 1
    Online Resource
    Online Resource
    Degradation mechanism of CH3NH3PbI3 perovskite materials upon exposure to humid air
    AIP Publishing ; 2016
    In:  Journal of Applied Physics Vol. 119, No. 11 ( 2016-03-21)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 119, No. 11 ( 2016-03-21)
    Abstract: Low stability of organic-inorganic perovskite (CH3NH3PbI3) solar cells in humid air environments is a serious drawback which could limit practical application of this material severely. In this study, from real-time spectroscopic ellipsometry characterization, the degradation mechanism of ultra-smooth CH3NH3PbI3 layers prepared by a laser evaporation technique is studied. We present evidence that the CH3NH3PbI3 degradation in humid air proceeds by two competing reactions of (i) the PbI2 formation by the desorption of CH3NH3I species and (ii) the generation of a CH3NH3PbI3 hydrate phase by H2O incorporation. In particular, rapid phase change occurs in the near-surface region and the CH3NH3PbI3 layer thickness reduces rapidly in the initial 1 h air exposure even at a low relative humidity of 40%. After the prolonged air exposure, the CH3NH3PbI3 layer is converted completely to hexagonal platelet PbI2/hydrate crystals that have a distinct atomic-scale multilayer structure with a period of 0.65 ± 0.05 nm. We find that conventional x-ray diffraction and optical characterization in the visible region, used commonly in earlier works, are quite insensitive to the surface phase change. Based on results obtained in this work, we discuss the degradation mechanism of CH3NH3PbI3 in humid air.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.4943638
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2016
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 2
    Online Resource
    Online Resource
    Dynamics of submicron microsphere suspensions observed by dynamic ultrasound scattering techniques in the frequency-domain
    AIP Publishing ; 2014
    In:  Journal of Applied Physics Vol. 115, No. 20 ( 2014-05-28)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 115, No. 20 ( 2014-05-28)
    Abstract: Dynamic ultrasound scattering (DSS) techniques have been employed in order to evaluate the dynamics and size of submicron-particles. In addition to the fact that the ultrasound-based techniques could be applied to optically turbid systems, a novel method called frequency-domain DSS allowed us to investigate complex fluid dynamics involving both thermal diffusion and settling of microspheres by recording the time-correlation function at the corresponding spatial length scales. While the particle sizing was successful for silica and polystyrene particles with the hydrodynamics radii down to 100 nm, which was 20 times smaller than the minimal detectable size in the previous DSS studies, coupling of diffusion and sedimentation modes was observed. Since it enables us to quantitatively evaluate the particle motions at the individual scanning windows by a single acquisition, diffusion and sedimentation of submicron particles were simultaneously analyzed at the corresponding scattering vectors where the contribution from sedimentation was neutralized by the density matching.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.4879235
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2014
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
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  • 3
    Online Resource
    Online Resource
    Dynamics of nanometer- and submicrometer-sized particles in suspension probed by dynamic ultrasound scattering techniques
    AIP Publishing ; 2017
    In:  Journal of Applied Physics Vol. 122, No. 4 ( 2017-07-28)
    Details
    In: Journal of Applied Physics, AIP Publishing, Vol. 122, No. 4 ( 2017-07-28)
    Abstract: The Dynamic ultraSound Scattering (DSS) technique, which is an acoustic analog of dynamic light scattering (DLS), has been developed to achieve particle sizing with a wide range of particle sizes from nanometers to micrometers. In the submicron regime, it was difficult to evaluate the particle size by DSS because of the competition between the Brownian and sedimentation motions as we addressed in the previous work [Igarashi et al., J. Appl. Phys. 115, 203506 (2014)]. We propose here a new function to evaluate the particle size in the submicron regime, and with 10% accuracy, the good agreement between DSS and Field-Emission Scanning Electron Microscopy results was confirmed. By improving the transducer, the recording system, as well as the analysis technique, the detectable particle size by the DSS technique now could be extended down to several tens of nanometers.
    Type of Medium: Online Resource
    ISSN: 0021-8979 , 1089-7550
    URL: Article
    DOI: 10.1063/1.4996352
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 220641-9
    detail.hit.zdb_id: 3112-4
    detail.hit.zdb_id: 1476463-5
    Location Call Number Limitation Availability
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