Dion-Jacobson Phase 2D Layered Perovskites for Solar Cells with Ultrahigh Stability

2D layered perovskites have emerged as potential alternates to traditional 3D analogs to solve the stability issue of perovskite solar cells (PSCs). However, van der Waals gaps in reported Ruddlesden-Popper (RP) phase 2D perovskites with monoammonium cations provide weak interactions between layers, potentially destabilizing the layered perovskite structure and thus the device. Here we eradicate such gaps by incorporating diammonium cations into MAPbI3, developing a series of Dion-Jacobson phase 2D perovskites that afford a cell efficiency of 13.3% with ultrahigh device stability. Unencapsulated devices retain over 95% efficiency upon exposure to various harsh stresses including ambient air (40%–70% relative humidity [RH]) for 4,000 hr, damp heat (85°C and 85% RH) for 168 hr, and continuous light illumination for 3,000 hr. The improved device stability over the RP counterpart is attributed to alternating hydrogen bonding interactions between diammonium cations and inorganic slabs, strengthening the 2D layered perovskite structure.