References of "Guennou, Mael"
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See detailNanometre-scale optical property fluctuations in Cu2ZnSnS4 revealed by low temperature cathodoluminescence
Mendis, B. G.; Taylor, A. A.; Guennou, Maël et al

in Solar Energy Materials & Solar Cells (2018), 174

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See detailSodium enhances indium-gallium interdiffusion in copper indium gallium diselenide photovoltaic absorbers
Colombara, Diego UL; Werner, Florian UL; Schwarz, Torsten et al

in Nature Communications (2018)

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See detailNanometre-scale optical property fluctuations in Cu2ZnSnS4 revealed by low temperature cathodoluminescence
Mendis, B. G.; Taylor, A. A.; Guennou, Mael et al

in Solar Energy Materials & Solar Cells (2017), 174

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See detailOrdering kesterite improves solar cells:A low temperature post-deposition annealing study
Rey, Germain UL; Weiss, Thomas UL; Sendler, Jan UL et al

in Solar Energy Materials & Solar Cells (2016), 151

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See detailBismuth-based perovskites as multiferroics
Guennou, Mael; Viret, Michel; Kreisel, Jens UL

in Comptes Rendus Physique (2015), 16(2), 182-192

This review devoted to multiferroic properties of bismuth-based perovskites is divided into two parts. The first one focuses on BiFeO3and summarizes the recent progress made in the studies of its ... [more ▼]

This review devoted to multiferroic properties of bismuth-based perovskites is divided into two parts. The first one focuses on BiFeO3and summarizes the recent progress made in the studies of its pressure–temperature phase diagram and magnetoelectric coupling phenomena. The second part discusses in a more general way the issue of polar—and multiferroic—phases in BiBO3perovskites and the competition between ferroelectricity and other structural instabilities, from an inventory of recently synthesized compounds. [less ▲]

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See detailQuantification of surface ZnSe in Cu2ZnSnSe4-based solar cells by analysis of the spectral response
Colombara, Diego UL; Robert, Erika UL; Crossay, Alexandre UL et al

in Solar Energy Materials & Solar Cells (2014), 123

Absorber layers consisting of Cu2ZnSnSe4 (CZTSe) and surface ZnSe in variable ratios were prepared by selenization of electroplated Cu/Sn/Zn precursors and completed into full devices with up to 5.6 ... [more ▼]

Absorber layers consisting of Cu2ZnSnSe4 (CZTSe) and surface ZnSe in variable ratios were prepared by selenization of electroplated Cu/Sn/Zn precursors and completed into full devices with up to 5.6 % power conversion efficiency. The loss of short circuit current density for samples with increasing ZnSe content is consistent with an overall reduction of spectral response, pointing to a ZnSe current blocking behavior. A feature in the spectral response centered around 3 eV was identified and attributed to light absorption by ZnSe. A model is proposed to account for additional collection of the carriers generated underneath ZnSe capable of diffusing across to the space charge region. The model satisfactorily reproduces the shape of the spectral response and the estimated ZnSe surface coverage is in good qualitative agreement with analysis of the Raman spectral mapping. The model emphasizes the importance of the ZnSe morphology on the spectral response, and its consequences on the solar cell device performance. [less ▲]

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See detailJahn-Teller, Polarity, and Insulator-to-Metal Transition in BiMnO3 at High Pressure
Guennou, Mael; Bouvier, Pierre; Toulemonde, Pierre et al

in Physical Review Letters (2014), 112

The interaction of coexisting structural instabilities in multiferroic materials gives rise to intriguing coupling phenomena and extraordinarily rich phase diagrams, both in bulk materials and strained ... [more ▼]

The interaction of coexisting structural instabilities in multiferroic materials gives rise to intriguing coupling phenomena and extraordinarily rich phase diagrams, both in bulk materials and strained thin films. Here we investigate the multiferroic BiMnO3 with its peculiar 6s2 electrons and four interacting mechanisms: electric polarity, octahedra tilts, magnetism, and cooperative Jahn-Teller distortion. We have probed structural transitions under high pressure by synchrotron x-ray diffraction and Raman spectroscopy up to 60 GPa. We show that BiMnO3 displays under pressure a rich sequence of five phases with a great variety of structures and properties, including a metallic phase above 53 GPa and, between 37 and 53 GPa, a strongly elongated monoclinic phase that allows ferroelectricity, which contradicts the traditional expectation that ferroelectricity vanishes under pressure. Between 7 and 37 GPa, the Pnma structure remains remarkably stable but shows a reduction of the Jahn-Teller distortion in a way that differs from the behavior observed in the archetypal orthorhombic Jahn-Teller distorted perovskite LaMnO3. [less ▲]

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See detailOrder-parameter symmetries of domain walls in ferroelectrics and ferroelastics
Toledano, Pierre; Guennou, Mael; Kreisel, Jens UL

in Physical Review B (2014), 89(13),

The symmetry of boundaries between ferroelectric, ferroelastic, and antiphase domains is a key element for a theoretical understanding of their properties. Here, we derive this symmetry from their organic ... [more ▼]

The symmetry of boundaries between ferroelectric, ferroelastic, and antiphase domains is a key element for a theoretical understanding of their properties. Here, we derive this symmetry from their organic relation to the symmetry of the primary transition order parameters. The domain wall symmetries are shown to coincide with directions of the order-parameter n-dimensional vector space, corresponding to sum of the vectors associated with adjacent domain states. This property is illustrated by the determination of the maximal symmetries of domain walls in BaTiO3, LaAlO3, SrTiO3, and Gd2(MoO4)3. Besides, the domain pattern in YMnO3 is interpreted as resulting from an annihilation-creation process, the annihilation of the antiphase domain walls creating six ferroelectric domain walls merging at a single point. [less ▲]

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See detailStructures and Magnetism of the Rare-Earth Orthochromite Perovskite Solid Solution LaxSm1−xCrO3
Daniels, Luke M.; Weber, Mads C.; Lees, Martin R. et al

in Inorganic Chemistry (2013), 52

A new mixed rare-earth orthochromite series, LaxSm1−xCrO3, prepared through single-step hydrothermal synthesis is reported. Solid solutions (x = 0, 0.25, 0.5, 0.625, 0.75, 0.875, and 1.0) were prepared by ... [more ▼]

A new mixed rare-earth orthochromite series, LaxSm1−xCrO3, prepared through single-step hydrothermal synthesis is reported. Solid solutions (x = 0, 0.25, 0.5, 0.625, 0.75, 0.875, and 1.0) were prepared by the hydrothermal treatment of amorphous mixed-metal hydroxides at 370 °C for 48 h. Transmission electron microscopy (TEM) reveals the formation of highly crystalline particles with dendritic-like morphologies. Rietveld refinements against high-resolution powder X-ray diffraction (PXRD) data show that the distorted perovskite structures are described by the orthorhombic space group Pnma over the full composition range. Unit cell volumes and Cr−O−Cr bond angles decrease monotonically with increasing samarium content, consistent with the presence of the smaller lanthanide in the structure. Raman spectroscopy confirms the formation of solid solutions, the degree of their structural distortion. With the aid of shell-model calculations the complex mixing of Raman modes below 250 cm−1 is clarified. Magnetometry as a function of temperature reveals the onset of low-temperature antiferromagnetic ordering of Cr3+ spins with weak ferromagnetic component at Néel temperatures (TN) that scale linearly with unit cell volume and structural distortion. Coupling effects between Cr3+ and Sm3+ ions are examined with enhanced susceptibilities below TN due to polarization of Sm3+ moments. At low temperatures the Cr3+ sublattice is shown to undergo a second-order spin reorientation observed as a rapid decrease of susceptibility. [less ▲]

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