Tracking Structural Phase Transitions in Lead-Halide Perovskites by Means of Thermal Expansion

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  • Masoumeh Keshavarz, Katholieke Universiteit Leuven, Belgium
  • ,
  • Martin Ottesen
  • Steffen Wiedmann, Radboud University Nijmegen
  • ,
  • Michael Wharmby, DESY Photon Science
  • ,
  • Robert Küchler, Max Planck Institute for Chemical Physics of Solids
  • ,
  • Haifeng Yuan, Katholieke Universiteit Leuven, Belgium
  • ,
  • Elke Debroye, Katholieke Universiteit Leuven, Belgium
  • ,
  • Julian A. Steele, KU Leuven
  • ,
  • Johan Martens, KU Leuven
  • ,
  • Nigel E. Hussey, Radboud University Nijmegen
  • ,
  • Martin Bremholm
  • Maarten B.J. Roeffaers, KU Leuven
  • ,
  • Johan Hofkens, Katholieke Universiteit Leuven, Belgium

The extraordinary properties of lead-halide perovskite materials have spurred intense research, as they have a realistic perspective to play an important role in future photovoltaic devices. It is known that these materials undergo a number of structural phase transitions as a function of temperature that markedly alter their optical and electronic properties. The precise phase transition temperature and exact crystal structure in each phase, however, are controversially discussed in the literature. The linear thermal expansion of single crystals of APbX3 (A = methylammonium (MA), formamidinium (FA); X = I, Br) below room temperature is measured using a high-resolution capacitive dilatometer to determine the phase transition temperatures. For δ-FAPbI3, two wide regions of negative thermal expansion below 173 and 54 K, and a cascade of sharp transitions for FAPbBr3 that have not previously been reported are uncovered. Their respective crystal phases are identified via powder X-ray diffraction. Moreover, it is demonstrated that transport under steady-state illumination is considerably altered at the structural phase transition in the MA compounds. The results provide advanced insights into the evolution of the crystal structure with decreasing temperature that are essential to interpret the growing interest in investigating the electronic, optical, and photonic properties of lead-halide perovskite materials.

Original languageEnglish
Article number1900521
JournalAdvanced Materials
Pages (from-to)1900521-1 til 1900521-8
Number of pages8
Publication statusPublished - Jun 2019

    Research areas

  • perovskites, structural phase transitions, thermal expansion

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