Dion-Jacobson and Ruddlesden-Popper double-phase 2D perovskites for solar cells

Dion-Jacobson (DJ) phase and Ruddlesden-Popper phase 2D perovskites have been, individually, demonstrated to be more stable than 3D counterparts for perovskite solar cells (PSCs). In order to further improve the efficiency and stability of 2D PSCs, we herein report merging them to construct a DJ:RP double-phase perovskite (DPP) structure for the first time. With the DJ 2D perovskite composed of diammonium as the matrix, a monoammonium with a larger size than the diammonium is incorporated to form an independent RP phase 2D perovskite coexisting with the DJ one (DJ:RP DPP structure), which facilitates crystal growth, suppresses charge recombination, and improves charge transport. As a comparison, introduction of a smaller monoammonium than the diammonium leads to its insertion between inorganic slabs, yielding a distorted DJ 2D perovskite structure, which induces lattice relaxation/distortion and thus lowered charge transportation. Consequently, 2D PSCs based on the DJ:RP DPP afford an impressive efficiency of 13.8% with excellent thermal stability at 85 degrees C in damp air. This work demonstrates a new and promising strategy of developing the DJ:RP DPP for highly efficient and robust 2D PSCs.