Time-Resolved Lattice Dynamics of Metal Halide Perovskite Nanomaterials

Metal halide perovskite nanoparticles show promise for a variety of optoelectronics purposes, including use in photovoltaics, LEDs, photocatalysts, and lasing applications. Many of the intended applications present nanomaterials with high energy, high intensity photoexcitation, raising interest in the transient or permanent electronic and thermal effects that such exposure might have on the crystal lattice. Structural rearrangements of nanomaterials in response to photoexcitation, such as lattice distortions and phase transitions, are also of particular interest, as these engender long carrier lifetime. We have been investigating the sensitivity of the nanoparticle lattice to photon irradiation of varying intensity and monitor the time-evolution of the lattice distortions using time-resolved X-ray diffraction (TRXRD). We compare different forms of hybrid organic-inorganic and fully inorganic CsPbI₃ perovskite nanoparticles and observe unexpected transient behaviors. We find that lattice distortions develop rapidly and recover with a range of timescales depending on composition. These studies, paired with evaluations of thermalization and phonon evolution studies offer improved insights into the design of nanomaterials for applications. 

1. Center for Nanoscale Materials, Argonne National Laboratory, Lemont, IL 60439 

2. Department of Chemistry, Northwestern University, Evanston, IL 60208