Halide perovskite semiconductors and solar cells respond to electric fields in a way that varies across time and length scales. We discuss the microscopic processes that give rise to the macroscopic polarization of these materials, ranging from the optical and vibrational response to the transport of ions and electrons. The strong frequency dependence of the dielectric permittivity can be understood by separating the static dielectric constant into its constituents, including the orientational polarization due to rotating dipoles, which connects theory with experimental observations. The controversial issue of ferroelectricity is addressed, where we highlight recent progress in materials and domain characterization but emphasize the challenge associated with isolating spontaneous lattice polarization from other processes such as charged defect formation and transport. We conclude that CH 3 NH 3 PbI 3 exhibits many features characteristic of a ferroelastic electret, where a spontaneous lattice strain is coupled to long-lived metastable polarization states.
Bibliographical noteFunding Information:
We thank P. R. F. Barnes, A. P. Horsfield, L. Herz, S. Stranks, and R. W. Whatmore for useful discussion on polarization, piezoresponse, and perovskites. This research has been funded by the EPSRC (Grant No. EP/K016288/1). A.W. is supported by a Royal Society University Research Fellowship. We are grateful to the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (No. EP/P020194/1). This research was also supported by the Creative Materials Discovery Program through the National Research Foundation of Korea (NRF) funded by Ministry of Science and ICT (2018M3D1A1058536).
All Science Journal Classification (ASJC) codes
- Materials Science(all)