Highly Anisotropic Polarization Induced by Electrical Poling in Single-Crystalline All-Inorganic Perovskite Nanoplates

The coupled ionic and electronic transport in halide perovskites opens up new possibilities for semiconductor iontronic devices beyond solar cells. Nevertheless, the fundamental understanding of ionic behavior at the microscale remains vague, largely because of the inhomogeneity in polycrystalline thin films. Here, we show that the ion dynamics in single-crystalline perovskite nanoplates (NPs) are significantly different and that an external bias may induce highly anisotropic ionic transport in the NPs, thereby leading to a greatly enhanced local electric field. Using modified scanning photocurrent microscopy (SPCM), the origin of the photocurrent is pinpointed to the cathode region of the NP device, where subsequent energy dispersive spectroscopy (EDS) characterization confirms a large accumulation of halogen vacancies. In addition, the Kelvin probe force microscopy (KPFM) measurement demonstrates a strong built-in electric field within a submicron length near the cathode, which alters the local electronic structure for efficient photo carrier separation. Such field-induced ionic behavior deepens the understanding of ion dynamics in perovskites and promotes scale-down of perovskite micro- and nanoiontronic and ion-optoelectronic devices.

Automated summary

The coupled transport of ions and electrons in halide perovskites can lead to highly anisotropic ionic transport and enhanced local electric fields. This study investigates the ion dynamics in single-crystalline perovskite nanoplates and demonstrates the influence of external bias on ion transport. The findings deepen the understanding of ion behavior in perovskites and have implications for downsizing micro- and nanoiontronic and ion-optoelectronic devices.