Intrinsic-polarization origin of photoconductivity in MAPbI3 thin films

Hybrid halide perovskites (HHPs) exhibit exceptional photoelectric properties, facilitating highly efficient modern solar cells and photoconductive technologies. Both ion migration and intrinsic spontaneous polarization have been proposed as the main source of enhanced photoelectric activity, but the exact origin of the advantageous properties has remained elusive. Here, we combined nanoscale and macroscale device characterization studies to demonstrate that intrinsic polarization conductivity governs photoconductivity in HHP films. Conductive atomic force microscopy under variable light and temperature conditions showed that the photocurrent in these materials is directional and flows along the long crystallographic axis, as opposed to other conduction mechanisms that prioritize the shortest path between the electrode and the conductive tip. It was also shown that the photocurrent is suppressed at the tetragonal-to-cubic transformation. The findings were confirmed by macroscale device measurements. Following the nonvolatile memory nature of polarization domains, photoconductive memristive behavior was demonstrated. Understanding the origin of photoelectric activity in HHPs allows designing devices with enhanced functionality.