| 1. |
- Cinquanta, Eugenio, et al.
(author)
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Ultrafast THz Probe of Photoinduced Polarons in Lead-Halide Perovskites
- 2019
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In: Physical Review Letters. - 0031-9007. ; 122:16
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Journal article (peer-reviewed)abstract
- We study the nature of photoexcited charge carriers in CsPbBr3 nanocrystal thin films by ultrafast optical pump-THz probe spectroscopy. We observe a deviation from a pure Drude dispersion of the THz dielectric response that is ascribed to the polaronic nature of carriers; a transient blueshift of observed phonon frequencies is indicative of the coupling between photogenerated charges and stretching-bending modes of the deformed inorganic sublattice, as confirmed by DFT calculations.
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| 2. |
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| 3. |
- Makowska, Malgorzata Grazyna, et al.
(author)
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Coupling between creep and redox behavior in nickel - yttria stabilized zirconia observed in-situ by monochromatic neutron imaging
- 2017
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In: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 340, s. 167-175
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Journal article (peer-reviewed)abstract
- Ni-YSZ (nickel - yttria stabilized zirconia) is a material widely used for electrodes and supports in solid oxide electrochemical cells. The mechanical and electrochemical performance of these layers, and thus the whole cell, depends on their microstructure. During the initial operation of a cell, NiO is reduced to Ni. When this process is conducted under external load, like also present in a stack assembly, significant deformations of NiO/Ni-YSZ composite samples are observed. The observed creep is orders of magnitude larger than the one observed after reduction during operation. This phenomenon is referred to as accelerated creep and is expected to have a significant influence on the microstructure development and stress field present in the Ni-YSZ in solid oxide electrochemical cells (SOCs), which is highly important for the durability of the SOC. In this work we present energy selective neutron imaging studies of the accelerated creep phenomenon in Ni/NiO-YSZ composite during reduction and also during oxidation. This approach allowed us to observe the phase transition and the creep behavior simultaneously in-situ under SOC operation-like conditions.
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| 4. |
- Sadd, Matthew, 1994, et al.
(author)
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Visualization of Dissolution‐Precipitation Processes in Lithium–Sulfur Batteries
- 2022
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In: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 12:10
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Journal article (peer-reviewed)abstract
- In this work, light is shed on the dissolution and precipitation processes S8 and Li2S, and their role in the utilization of active material in Li-S batteries. Combining operando X-ray Tomographic Microscopy and optical image analysis, in real-time; sulfur conversion/dissolution in the cathode, the diffusion of polysulfides in the bulk electrolyte, and the redeposition of the product of the electrochemical reaction, Li2S, on the cathode are followed. Using a custom-designed capillary cell, positioning the entire cathode volume within the field of view, the conversion of elemental sulfur to soluble polysulfides during discharge is quantitatively followed. The results show the full utilization of elemental sulfur in the cathode in the initial stage of discharge, with all solid sulfur converted to soluble polysulfide species. Optical image analysis shows a rapid diffusion of polysulfides as they migrate from the cathode to the bulk electrolyte at the start of discharge and back to the cathode in the later stages of discharge, with the formation and precipitation of Li2S. The results point to the redeposition of Li2S on all available surfaces in the cathode forming a continuous insulating layer, leaving polysulfide species remaining in the electrolyte, and this is the process limiting the cell's specific capacity.
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| 5. |
- Shukla, Aditya, et al.
(author)
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Grain boundary strain localization in a CdTe solar cell revealed by scanning 3D X-ray diffraction microscopy
- 2024
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In: Journal of Materials Chemistry A. - 2050-7488. ; 12:27, s. 16793-16802
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Journal article (peer-reviewed)abstract
- Cadmium telluride (CdTe) solar cell technology is a promising candidate to help boost green energy production. However, impurities and structural defects are major barriers to improving the solar power conversion efficiency. Grain boundaries often act as aggregation sites for impurities, resulting in strain localization in areas of high diffusion. In this study, we demonstrate the use of scanning 3D X-ray diffraction microscopy to non-destructively make 3D maps of the grains - their phase, orientation, and local strain - within a CdTe solar cell absorber layer with a resolution of 100 nm. We quantify twin boundaries and suggest how they affect grain size and orientation distribution. Local strain analysis reveals that strain is primarily associated with high misorientation grain boundaries, whereas twin boundaries do not have high strain values. We also observe that high-strain grain boundaries form a continuous pathway connected to the CdS layer. Hence, this high-strain region is believed to be associated with the diffusion of sulfur from the CdS layer along grain boundaries. This hypothesis is supported by SEM-EDS and X-ray fluorescence experiments. The method and analysis demonstrated in this work can be applied to different polycrystalline materials where the characterization of grain boundary properties is essential to understand the microstructural phenomena.
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