Regensburg 2022 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 28: Perovskite and Photovoltaics 3
CPP 28.3: Vortrag
Mittwoch, 7. September 2022, 15:30–15:45, H38
Hidden interfaces: How ferroelastic domain walls affect the charge diffusion in perovskite solar cells — •Ilka M. Hermes1,2, Andreas Best2, Kaloian Koynov2, Hans-Jürgen Butt2, and Stefan A. L. Weber2 — 1Leibniz Institute for Polymer Research Dresden e.V., Dresden, Germany — 2Max Planck Institute for Polymer Research, Mainz, Germany
Ferroelastic domains form during phase transitions that change the crystal system. By arranging in domains with alternating unit cell orientation, the material lowers its overall strain. The walls that separate ferroelastic domains typically feature some structural anomalies, which can affect the electronic properties of the crystal by increasing the defect concentration, introducing dopants or forming a local electric polarization via the flexoelectric effect. Here, we explored the implications of ferroelastic domain walls for the photo-carrier transport in methylammonium lead iodide, a solar cell light absorber used in perovskite solar cells. Via correlative spatial and time-resolved photoluminescence microscopy and electromechanical atomic force microscopy, we could link the presence of domain walls to the occurrence of an anisotropic charge diffusion, where charges move faster parallel to domain walls than perpendicular. Moreover, the ferroelastic nature of the domains promises a targeted engineering of the domain wall arrangement using the application of external stress or heat treatments across the material's cubic-tetragonal phase transition: a perpendicular alignment of the domain walls with respect to the extraction layer interfaces should facilitate faster and more efficient charge extraction.