Enhanced Out-of-Plane Conductivity and Photovoltaic Performance in <i>n</i> = 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.