General description

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Synopsis

The mission of the SNBL is to provide scientists from both Norway and Switzerland, from both academia and industry, with increased access to synchrotron radiation. A user on SNBL has access to state-of-the-art, custom-designed instrumentation for diffraction and absorption experiments. Both partner countries have relatively large and exceptionally active scientific communities using X-ray diffraction and absorption as their main probes; for these groups the amount of public beamtime offered by ESRF was insufficient from day one, and this is the raison d’être of the Swiss-Norwegian Beam Lines at ESRF. Nowadays, it is fully understood by the  scientific community that many of the most challenging problems in structural crystallography can be solved only with the use of synchrotron radiation, and even  then, often enough, only by harnessing the combined power of two or more experimental techniques (such as, e.g., powder and single-crystal diffraction). The SNBL has four such different experimental techniques, which are distributed over two beamlines, and presently include:

  • High-resolution single-crystal diffractometry

  • Large-area diffraction imaging

  • High-resolution powder diffractometry

  • EXAFS spectrometry

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“SNBL – Planning for the next decade”(programme) - Photos by Serge Claisse (ILL)

Number of publications from SNBL


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ESRF Young Scientist Award goes to SNBL scientist

Highlights

Structure and interstitial iodide migration in hybrid perovskite methylammonium lead iodide

Hybrid perovskites form an emerging family of exceptional light harvesting compounds. However, the mechanism underpinning their photovoltaic effect is still far from understood, which is impeded by a lack of clarity on their structures. Here we show that iodide ions in the methylammonium lead iodide migrate via interstitial sites at temperatures above 280 K. This coincides with temperature dependent static distortions resulting in pseudocubic local symmetry. Based on bond distance analysis, the migrating and distorted iodines are at lengths consistent with the formation of I2 molecules, suggesting a 2I−→I2+2e− redox couple. The actual formula of this compound is thus (CH3NH3)PbI3−2x(I2)x where x∼0.007 at room temperature. A crucial feature of the tetragonal structure is that the methylammonium ions do not sit centrally in the A-site cavity, but disordered around two off-centre orientations that facilitate the interstitial ion migration via a gate opening mechanism.

Nature Communications 8, 2017

 

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