Polarization Origin of Photoconductivity in MAPbI3 Thin Films

TL;DR

This study reveals that polarization-assisted conductivity, rather than ion migration, is the main driver of photoconductivity in MAPbI3 thin films, enabling the development of advanced photoelectric and memristive devices.

Contribution

It demonstrates that polarization, not ion migration, governs photoconductivity in hybrid-halide perovskite films through combined microscale and device-scale analysis.

Findings

Polarization-assisted conductivity is directional and suppressed at phase transition.

Dark conductivity is dominated by ion migration, non-directional.

Photoconductive memristive behavior is demonstrated.

Abstract

Hybrid-halide perovskite (HHP) films exhibit exceptional photo-electric properties. These materials are utilized for highly efficient solar cells and photoconductive technologies. Both ion migration and polarization have been proposed as the source of enhanced photoelectric activity, but the exact origin of these advantageous device properties has remained elusive. Here, we combined microscale and device-scale characterization to demonstrate that polarization-assisted conductivity governs photoconductivity in thin HHP films. Conductive atomic force microscopy under light and variable temperature conditions showed that the photocurrent is directional and is suppressed at the tetragonal-to-cubic transformation. It was revealed that polarization-based conductivity is enhanced by light, whereas dark conductivity is dominated by non-directional ion migration, as was confirmed by large-scale device measurements. Following the non-volatile memory nature of polarization domains, photoconductive memristive behavior was demonstrated. Understanding the origin of photoelectric activity in HHP allows designing devices with enhanced functionality and lays the grounds for photoelectric memristive devices.