Crystal structures and phase transitions of the Methylammonium Tin Halide Perovskites

Fujihisa, Yui*; Takahashi, Miwako*; Hagihara, Masato   ; Torii, Shuki*; Kamiyama, Takashi*; Ohara, Takashi   ; Noda, Yukio*

Methylammonium Tin Halide Perovskites CHNHSnX (MASnX, X: halide) are candidates of lead-free light- absorbing materials for photovoltaic devices. They undergo successive phase transitions caused by tilting or distorting of the SnX octahedra and orientational ordering of the organic MA cation. The structures of low temperature phases are still controversial due to the difficulty of accurate determination for the orientation of organic cation. In this study, neutron diffraction measurements were performed on MASnX with X=I, Br to determine the structures at low temperature phases and elucidate the ordering mechanism of the organic cation through the phase transitions. Time-of-flight neutron diffraction data were collected using single crystal diffractometer SENJU (BL18) and Super High Resolution Powder Diffractometer SuperHRPD (BL08) installed at Materials and Life Science Experimental Facility, J-PARC.