Regulating microstructure of organic ammonium cations enables interface defect management and stability improvement in 2D/3D perovskite solar cells

Abstract

Two-dimensional (2D) perovskites with tunable spacer cations show considerable photoelectric properties and thus make great application prospect for 2D/3D heterojunction perovskite solar cells (PSCs). Herein, three quaternary ammonium cations (tetraethylammonium, tetrapropylammonium and tetrabutylammonium) with specific microstructure are employed to modify perovskite/hole transport layer interface. The influence of cation configuration on the crystallization, defect density and carrier transport of the 2D/3D films has been systematically studied. Owing to strong ionic interactions with peovskite crystal terminal, stable 2D perovskite barriers will be formed to block the migration channel of water molecules in air and organic ions in perovskite, leading to the improved stability of PSCs. More importantly, both the positive and negative defects could be effectively passivated attributing to the surfactant and amphoteric properties of quaternary ammonium cations. As a result, the optimal perovskite device modified by tetrabutylammonium shows the best power conversion efficiency (PCE) of 21.92 % with high Voc of 1.17 V and superior humidity and thermal resistance. Our work provides a simple and effective strategy to stabilize the interface in PSCs and verifies the role of cation microstructure in modulating the properties of 2D perovskite.