Dion-Jacobson (DJ) phase 2D layered perovskites are developed by removing the van der Waals gap between organic layers and inorganic slabs in Ruddlesden-Popper (RP) phase counterparts. The hydrogen bonding formed at both sides of diammonium cations with perovskite layers in the DJ phase 2D perovskite endows it with extremely high structural stability, compared with that at only one side in the RP phase one. The devices exhibit a PCE of 13.3% with unprecedented stability, even when subjected to very harsh testing conditions.

The integrated architecture enables the Ta3N5photoanode to approach the theoretical photocurrent limit for solar water splitting.