Enhanced Out-of-Plane Conductivity and Photovoltaic Performance in n = 1 Layered Perovskites through Organic Cation Design

Layered perovskites with the formula (R-NH₃)₂PbI₄ have excellent environmental stability but poor photovoltaic function due to the preferential orientation of the semiconducting layer parallel to the substrate and the typically insulating nature of the R-NH₃ ⁺ cation. Here, we report a series of these n = 1 layered perovskites with the form (aromatic-O-linker-NH₃)₂PbI₄ where the aromatic moiety is naphthalene, pyrene, or perylene and the linker is ethyl, propyl, or butyl. These materials achieve enhanced conductivity perpendicular to the inorganic layers due to better energy level matching between the inorganic layers and organic galleries. The enhanced conductivity and visible absorption of these materials led to a champion power conversion efficiency of 1.38%, which is the highest value reported for any n = 1 layered perovskite, and it is an order of magnitude higher efficiency than any other n = 1 layered perovskite oriented with layers parallel to the substrate. These findings demonstrate the importance of leveraging the electronic character of the organic cation to improve optoelectronic properties and thus the photovoltaic performance of these chemically stable low n layered perovskites.