Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Hybrid organic-inorganic halide perovskites represent a promising next-generation photovoltaic material with drawbacks on structure stability and composition concerns. Demonstrations of ion migration and molecular dynamics suggest room for structural contraction and subsequent property adjustments. Here, we have deployed dielectric and infrared spectroscopy under external pressure to probe the full structural phase diagram and dielectric response of methylammonium lead halide perovskites CH₃NH₃$PbX₃ (X = I, Br, or Cl). Ion migration can be fully suppressed by pressure beyond 4 GPa. The low-temperature orthorhombic phase transition can be gradually enhanced and stabilized at ambient conditions with increasing pressure. A slow relaxation mode, presumably the motion of the CH₃NH₃+ cation, is observed at lower pressure and is absent in the orthorhombic phase for every halide.