Bidirectional Photocurrents Induced by Ferrocene Spacers in Layered Hybrid Perovskites

Abstract As our technology advances, the demand for more functional semiconductor materials has grown. In layered hybrid perovskites, an enhanced functionality can be achieved by introducing molecular switches as spacers. These spacers permit the reversible modulation of the semiconductor properties, which can, for example, induce distinct photoresponses. In particular, negative and positive photocurrents (NPC, PPC) hold much potential for multistate photosensing. However, NPC in a single-layered hybrid perovskite material remains currently unknown. Here, we report on NPC and PPC in layered Dion-Jacobson-like and Ruddlesden–Popper hybrid perovskites induced by a switchable ferrocene-based spacer. Electronic communication in the form of charge transfer between the ferrocene moiety and the perovskite framework was confirmed via transient absorption spectroscopy. Under an external electric field, the ferrocene-induced charge carriers are rearranged into space charge zones, which quenches the conductivity, resulting in the NPC. This charge carrier arrangement is prohibited in Ruddlesden–Popper phases due to the presence of a van der Waals gap, leading to the PPC. Furthermore, NPC can also be realized for hybrid perovskites with different band gaps by adjusting bromide and iodide contents, highlighting the potential of spacer-induced photocurrents as the semiconductor properties can be tuned as needed.