Aryl-Perfluoroaryl Interaction in Two-Dimensional Organic–Inorganic Hybrid Perovskites Boosts Stability and Photovoltaic Efficiency

Two-dimensional (2D) organic–inorganic
hybrid perovskites
(OIHPs) have showed impressive stability, compared to their three-dimensional
(3D) counterparts. However, tuning the chemical structure of the organic
cations to simultaneously improve the device performance and stability
of 2D OIHP solar cells is rarely reported. Here, we demonstrate that
by introducing a classic noncovalent aryl-perfluoroaryl interaction,
2D OIHP solar cells with 1:1 mixed phenethylammonium (PEA) and perfluorophenethylammonium
(F5-PEA) can achieve an efficiency of >10% with much enhanced stability
using a simple deposition at low temperature without using any additives.
The competing effects of surface morphology and crystal orientation
with an increased amount of F5-PEA result in the highest efficiency
at a 1:1 ratio, while single-crystal studies reveal the expected aryl-perfluoroaryl
interaction, accounting for the highest device stability of 2D OIHP
solar cell at 1:1 ratio as well. This work provides an example where
tuning the interactions of organic cations via molecular engineering
can have a profound effect on device performance and stability of
2D OIHP solar cells.