Enhancing Photovoltaic Performance of Aromatic Ammonium‐based Two‐Dimensional Organic‐Inorganic Hybrid Perovskites via Tuning CH···π Interaction

Phenethylammonium (PEA)‐based 2D perovskite is an interesting example of 2D perovskites, serving as the gateway for further introduction of functional conjugated organic cations into 2D perovskites for a variety of applications, for example, photovoltaics. However, the efficiency of photovoltaic devices based on PEA 2D perovskites only achieved ≈7% for <n> = 3, which was significantly lower than that achieved for other cation‐based 2D perovskites. Here, by introducing propyl ammonium (C3A) into the PEA‐based 2D perovskites, the device efficiency is improved to ≈10% for 1:1 C3A:PEA‐based 2D perovskites (<n> = 3). Further investigation reveals that tuning the CH···π interaction (between C3A and PEA or between two PEA molecules) can have multiple beneficial impacts on such modified 2D perovskites, including a) removal of undesirable n = 1 phase, b) lowering the density of trap states, and c) achieving larger crystalline grains. Additionally, after substitution with 50% C3A, other aromatic ammonium cation‐based 2D perovskites (<n> = 3) also show similar efficiency enhancement in their photovoltaic devices, thus exhibiting the general applicability of this method. The results of this study highlight that the strategic tuning of non‐covalent interactions (such as CH···π interaction) is a viable and important method to further develop 2D perovskites for photovoltaics.