Controlled dion-jacobson low-dimensional surface phase enables highly efficient and stable perovskite solar cells

The 2D/3D heterojunction structure emerges as a viable approach for enhancing the efficiency and stability of perovskite photovoltaics. However, the formation of an accumulative low-dimensional 2D perovskite (n=1) cladding layer often impedes carrier transport due to the insulating nature and high quantum confinement, and there is a paucity of detailed understanding regarding its surface phase control. This study introduces a Dion-Jacobson (DJ) phase 2D perovskite, employing decane-1,10-diammonium diiodide (DDADI) to interface with 3D perovskite, leveraging long-chain diammonium cations for structural stability and defect passivation on the 3D FAPbI3 perovskite surface. In addition, a novel PbI2-assisted phase control (PAPC) technique is proposed to mitigate the quantum confinement effects of the 2D layer, especially reducing the formation of the highly confined insulating n=1 phase. X-ray scattering analysis confirms the method's efficacy in promoting the formation of an n=2 phase, facilitating cascading HOMO levels and improving hole carrier transport. The optimized 2D/3D perovskite solar cell (PSC) achieve an exemplary efficiency of 25.16%, with a notable open-circuit voltage of 1.192 V, and retain 92.9% of its initial efficiency after 1000 hours in a nitrogen atmosphere, signifying a strategic advancement in 2D/3D PSC construction.