Diammonium cation pre-intercalation into inorganic framework for efficient Dion-Jacobson perovskite solar cells

The two-dimensional and three-dimensional (2D/3D) perovskite heterojunction has garnered significant attention in perovskite solar cells (PSCs) owing to the superior stability, modified band alignment and suppressed defects. Here, a pre-intercalation strategy involving bulky cations into inorganic framework to construct a buried 2D/3D perovskite heterojunction is proposed. The incorporation of bulky cation into PbI2 not only leads to the formation of well-oriented 2D nanoplates, but also disrupts the compact inorganic structure. It results in substantially increased grain boundaries at the buried interface, facilitating the complete reaction with small cations. Additionally, the pre-intercalated bulky cation acts as a template for the oriented growth of perovskite layer, leading to significantly reduced defects, enlarged crystal size and enhanced orientation. Furthermore, the advanced formation of buried 2D phases constructs a bottom-up 2D/3D perovskite heterojunction, enhancing carrier extraction and reducing energy loss in the PSCs. The resulting PSC achieves a champion power conversion efficiency of 23.40 %, surpassing the control device of 20.64 %. Moreover, the PSC maintains 88 % of its initial efficiency after 1050 h continuous efficiency tracking and retains over 97 % of its performance for 2232 h under a low humidity condition. Therefore, the pre-intercalation strategy represents a promising approach for both efficiency and stability challenges in PSCs.