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 (FS-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.