Influence of A-Site Composition on the Nanostructure and Electrical Properties of APbI₃ Perovskite Films: Implications for Solar Cells

Solar cells incorporating perovskite films with a blend of A-site cations have gained significant attention due to their enhanced stability and high-power conversion efficiencies. However, the relationship between the microstructure, electrical properties of perovskite films, compositions of A-site cations, and their correlation with the charge carrier dynamics of perovskite solar cells remains unknown. In this study, we investigated the electrical properties of APbI 3 perovskite films with varying A-site cations (A = Cs, CsFA, CsFAMA) at the grain boundaries (GBs) and grain interiors (GIs) using advanced probing microscopies. Measurements conducted with voltage-controlled Kelvin probe force microscopy (KPFM) confirmed the presence of ion motion within the perovskite films. By altering the illumination conditions, both KPFM and conductive atomic force microscopy measurements reveal that the hysteresis of CsFA perovskite thin film was significantly greater than that of CsPbI 3 and CsFAMA. Moreover, the variation in potential between the three thin films in the GB region and adjacent GI indicates the existence of band bending in the GB region of all three thin films. These findings are crucial for identifying the role of A-site cations in determining the electrical properties of perovskite films in relation to GIs and GBs, thereby facilitating further enhancements in photovoltaic devices through compositional engineering.