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Perovskite materials: Neutrons show twinning in halide perovskites

Date:
October 13, 2020
Source:
Helmholtz-Zentrum Berlin für Materialien und Energie
Summary:
Solar cells based on hybrid halide perovskites achieve high efficiencies. These mixed organic-inorganic semiconductors are usually produced as thin films of microcrystals. An investigation with the Laue camera at the neutron source BER II could now clarify that twinning occurs during crystallisation even at room temperature. This insight is helpful for optimising production processes of halide perovskites.
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A good ten years ago, research teams discovered the class of semi-organic halide perovskites, which are now making a rapid career as new materials for solar cells. The mixed organic-inorganic semiconductors achieved efficiencies of over 25 percent within a few years. They take their name from their basic structure, which is very similar to that of the mineral perovskite (CaTiO3), but contains other components: halide anions, lead cations and organic molecular cations.

In the case of the most important compound of the class, methylammonium lead iodide CH3NH3PbI3 (usually abbreviated as MAPI), which was also studied here, the molecular cations are methylammonium cations and the anions are iodide anions. Although more than 4000 publications on halide perovskites have appeared in 2019 alone, it has not yet been possible to fully understand their structure. In the case of MAPI this was attributed, among other things, to the fact that they are produced as polycrystalline films at elevated temperature and it was assumed that twinning occurs when they are cooled to room temperature.

The formation of twins is complex and can significantly change the material properties. It is therefore exciting to investigate this process more closely. "We have now crystallised MAPI at room temperature and analysed the crystals thus formed with the Laue camera Falcon on BER II," says Dr. Joachim Breternitz, HZB. Together with his colleagues Prof. Susan Schorr and Dr. Michael Tovar, he was able to determine from the data that crystals grown at room temperature also form twins. This gives a new insight into the crystallization and growth process of MAPI. "Our results indicate that the crystallisation nuclei have a higher symmetry than the bulk crystals," explains Breternitz.

With these insights, the synthesis of the technologically important thin films can be specifically optimised.

The neutron source BER II has provided neutrons for research until its scheduled shutdown in December 2019. "This was one of our last experiments at FALCON on BER II and I hope that we were able to make useful contributions right up to the end," says Breternitz.


Story Source:

Materials provided by Helmholtz-Zentrum Berlin für Materialien und Energie. Note: Content may be edited for style and length.


Journal Reference:

  1. Joachim Breternitz, Michael Tovar, Susan Schorr. Twinning in MAPbI3 at room temperature uncovered through Laue neutron diffraction. Scientific Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-73487-1

Cite This Page:

Helmholtz-Zentrum Berlin für Materialien und Energie. "Perovskite materials: Neutrons show twinning in halide perovskites." ScienceDaily. ScienceDaily, 13 October 2020. <www.sciencedaily.com/releases/2020/10/201013124121.htm>.
Helmholtz-Zentrum Berlin für Materialien und Energie. (2020, October 13). Perovskite materials: Neutrons show twinning in halide perovskites. ScienceDaily. Retrieved July 14, 2024 from www.sciencedaily.com/releases/2020/10/201013124121.htm
Helmholtz-Zentrum Berlin für Materialien und Energie. "Perovskite materials: Neutrons show twinning in halide perovskites." ScienceDaily. www.sciencedaily.com/releases/2020/10/201013124121.htm (accessed July 14, 2024).

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