Vertical Orientated Dion–Jacobson Quasi‐2D Perovskite Film with Improved Photovoltaic Performance and Stability

Abstract Dion–Jacobson (DJ) phase 2D layered perovskites with diammonium organic cations demonstrate improved stability over 3D perovskites under thermal/photo/moisture stresses. However, the power conversion efficiency (PCE) of DJ phase perovskite solar cells (PVSCs) is often limited by the poor charge transport across the perovskite layers due to the crystal growth direction that tends to be parallel to the substrate. Here, a simple and effective method is demonstrated by employing a NH 4 SCN additive to facilitate the orientation of perovskite crystal growth to be perpendicular to the substrate. Also, the layer number distribution can be narrowed to around n = 3 and n = 4 with NH 4 SCN addition. The device derived from the quasi‐2D DJ (BDA)(MA) 4 Pb 5 I 16 perovskite film processed with NH 4 SCN shows a PCE of 14.53%, which is among the highest values reported for 2D PVSCs prepared at room temperature. Moreover, the device retains 85% of its initial PCE after 900 h storage in ambient conditions with a humidity level of 50 ± 5%. These results demonstrate that this attractive approach will enable highly efficient and stable PVSCs to be made for renewable energy applications.