Dion-Jacobson 2D-3D perovskite solar cells with improved efficiency and stability

Abstract Ruddlesden-Popper (RP) two-dimensional (2D) perovskites have been employed on the top of three-dimensional (3D) perovskites as a capping layer to improve the efficiency and stability of perovskite solar cells (PSCs). However, monoammonium-based RP 2D perovskites possess an unsatisfactory structural stability because of weak van der Waals interactions between interlayers. In this work, we report a more stable alternative, Dion-Jacobson (DJ) 2D perovskite based on the octyldiammonium cation, to construct a DJ 2D perovskite layer on the top of 3D perovskite for PSCs. The in situ grown DJ 2D perovskite layer on the 3D one plays crucial roles in improving not only the PSC stability contributed by its intrinsically stable structure without the weak van der Waals interactions but also the device efficiency because of the formation of cascade HOMO levels favorable for hole transfer and extraction. Consequently, unencapsulated DJ 2D-3D PSCs afford a best efficiency of 21.6% with high stability under a constant relative humidity of 85%, much better than RP 2D-3D and 3D counterparts. This work offers a promising strategy to fabricate efficient and stable PSCs based on the DJ 2D-3D perovskite bilayer.