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Organic-inorganic hybrid perovskites as promising light-harvesting materials have been the focus of scientific research and development of photovoltaics recently. Especially, metal halide perovskites currently become one of the most competitive candidates for the fabrication of solar cells with record certified efficiency over 25%. Despite the high efficiency, many fundamental questions remain unclear and need to be addressed at both the material and device levels, such as weaker stability, poorer reproducibility, easier degradation influenced by water, oxygen, thermal factors, and so on. Based on recent reports, interfacial engineering plays a crucial role in controlling the behavior of the charge carriers and in growing high quality, defect-free perovskite crystals, therefore helping to enhance device performance and operational stability. However, little attention has been paid to the interface interaction mechanism among carrier transport layers and perovskite active layer. It is extremely urgent to explore the perovskite interfaces in details and to find out how its interface structure is relative to the efficiency and hysteresis in perovskites solar cells. Based on the Shanghai Synchrotron Radiation Facility (SSRF), we have established an advanced perovskite photovoltaic device preparation and in-line test system, developed a series of unique surface diffraction analysis methods based on ex situ and in situ grazing incidence X-ray diffraction (GIXRD), and reported a large number of novel synchrotron radiation results on crystallization of the perovskite photovoltaics films. Our main investigations are aimed to deeply in-situ study the perovskite film growth dynamics using synchrotron radiation GIXRD technology in combination with a customized mini online glove box (c(H2O,O2)

The temperature stability of cubic TiO1.05 titanium monooxide is investigated. An in situ X-ray structural analysis is performed using synchrotron radiation in a high temperature vacuum chamber. It is found that under poor vacuum and at high heating rates of up to 1250 C, the structural transformations in TiO1.05 occur at 630 C. In particular, there is a phase transition from TiO1.05 (space group Fm-3m) to rhombohedraic Ti2O3 (space group R-3c) via Ti2.5O3 (space group Immm). © 2013 Allerton Press, Inc.

International audience; Silicon clathrates are unusual open-framework solids formed by tetrahedrally bonded silicon that show remarkable electronic and thermal properties. The type I structure has a primitive cubic unit cell containing cages occupied by metal atoms to give compositions such as Na(8)Si(46) and Na(2)Ba(6)Si(46). Although their structure and properties are well described, there is little understanding of the formation mechanism. Na(8)Si(46) is typically produced by metastable thermal decomposition under vacuum conditions from NaSi, itself an unusual structure containing Si(4)(4-) polyanions.,In this study, we used in situ synchrotron X-ray diffraction combined with rapid X-ray detection on samples taken through a controlled temperature ramp (25-500 degrees C at 8 degrees C/min) under vacuum conditions (10(-4) bar) to study the clathrate formation reaction. We also carried out complementary in situ high-temperature solid-state (23)Na NMR experiments using a sealed tube loaded under inert-gas-atmosphere conditions. We find no evidence for an intermediate amorphous phase during clathrate formation. Instead, we observe an unexpectedly high degree of structural coherency between the Na8Si46 clathrate and its NaSi precursor, evidenced by a smooth passage of several X-ray reflections from one structure into the other. The results indicate the possibility of an unusual, epitaxial-like, growth of the dathrate phase as Na atoms are removed from the NaSi precursor into the vacuum.