research papers
Structure, symmetry and hydrogen bonds have been determined for pristine and aged tetragonal CH3NH3PbI3 crystals upon H2O absorption from air at room temperature. Single-crystal X-ray diffraction data obtained on a synchrotron light source was used for the study. H2O insertion into the structure changes hydrogen bonds and, consequently, the space group from I422 (pristine crystal) to P42212 (aged crystal).