Field-Induced Transport Anisotropy in Single-Crystalline All-Inorganic Lead-Halide Perovskite Nanowires

The dynamic crystal lattice of halide perovskites facilitates the coupled transport of ions and electrons, offering innovative concepts in semiconductor iontronic devices that surpass solar cell applications. However, a comprehensive understanding of the intricacies of coupled ionic and electronic transport at the microscale remains ambiguous, owing to the inhomogeneity in ploy-crystalline perovskite thin films. In this work, we employed one-dimensional (1D) single-crystalline CsPbBr₃ nanowires (NWs) to investigate the electric field induced ionic transport. Upon poling by an external bias, the previously uniform NW exhibits highly anisotropic ionic transport, which is identified as the origin of the giant switchable photovoltaic effect by spatially resolved scanning photocurrent microscopy. The subsequent ultrafast scanning photoluminescence (PL) microscopy measurements demonstrate significant localization of photocarriers near one terminal of the device, which is attributed to the accumulation of halogen vacancies. In addition, thanks to the enhancement of the local electric field, the poled device shows a 10-fold increase of photoresponse speed. Our findings favor the scale-down of perovskite devices to the submicrometer scale, extending their applications in self-powered iontronic and optoelectronic devices.