Emerging Conductive Atomic Force Microscopy for Metal Halide Perovskite Materials and Solar Cells

Metal halide perovskite materials, benefiting from a combination of outstanding optoelectronic properties and low-cost solution-preparation processes, show tremendous potential for optoelectronics and photovoltaics. However, the nanoscale inhomogeneities of the electronic properties of perovskite materials cause a number of difficulties, such as recombination, stability, and hysteresis, all of which seriously restrict device performance. Scanning probe microscopy, as a high-resolution imaging technique, has been widely used to connect local properties and micro-area morphologies to overall device performance. Conductive atomic force microscopy (C-AFM) can realize a real-space visualization of topography coupled with optoelectronic properties on a microscopic scale and thereby is uniquely suited to probe the local effects of perovskite materials and devices. The fundamental principles, alternative operation modes, and development of C-AFM are comprehensively reviewed, and applications in perovskite solar cells (PSCs) for electronic transport behavior, ion migration and hysteresis, ferroelectric polarization, and facet orientation investigation are discussed. A comprehensive understanding and summary of up-to-date applications in PSCs is beneficial to further fully exploit the potential of such an emerging technique, so as to provide a novel and effective approach for perovskite materials analysis.