High-pressure behavior of methylammonium lead iodide (MAPbI3) hybrid   perovskite
  In this paper we provide an accurate high-pressure structural and optical study of MAPbI3 hybrid perovskite. Structural data show the presence of a phase transition towards an orthorhombic structure around 0.3 GPa followed by full amorphization of the system above 3 GPa. After releasing pressure the systems keeps the high-pressure orthorhombic phase. The occurrence of these structural transitions is further confirmed by pressure induced variations of the photoluminescence signal at high pressure. These variations clearly indicate that the bandgap value and the electronic structure of MAPI change across the phase transition. 
Francesco Capitani, Carlo Marini, Simone Caramazza, Paolo Postorino,   Gaston Garbarino, Michael Hanfland, Ambra Pisanu, Pao...
cond-mat.mtrl-sci