Aromatic Heterocyclic Organic Spacer Cation-Assisted Growth of Large-Grain-Size 2DRP Perovskite Film for Enhanced Solar Cell Performance

Organic spacer cations play an important role in the aggregation of two-dimensional Ruddlesden–Popper (2DRP) L′2Ln–1BnX3n+1 perovskite precursors. Therefore, it is necessary to study how mixed A′ spacer cations affect the aggregation behavior of precursors and the carrier transport properties of 2DRP films. Herein, a novel spacer cation 4-pyridinylmethylammonium (PyA) is introduced to prepare a new mixed spacer cation 2DRP (BA1–xPyAx)2MA3Pb4I13 perovskite. The incorporation of PyA suppresses the precursor aggregation and reduces the transformation energy of the sol–gel to the directional three-dimensional phase, leading to the formation of large-grain-size 2DRP perovskite films. The PyA-based 2DRP perovskite exhibits efficient carrier transport owing to fewer defects and suppressed nonradiative recombination. Thus, the champion efficiency of 13.01% is achieved for BA- and PyA-based devices. The unencapsulated PyA-based devices maintain 98% of their initial efficiency after storage under nitrogen atmosphere for 1200 h. This work paves the way for preparing a large-grain-size 2DRP perovskite by suppressing precursor aggregation.