Reconstruction and Solidification of Dion–Jacobson Perovskite Top and Buried Interfaces for Efficient and Stable Solar Cells

Quasi-two-dimensional (Q-2D) perovskites show great potential in the field of photonic and optoelectronic device applications. However, defects and local lattice dislocation still limit performance and stability improvement by nonradiative recombination, unpreferred phase distribution, and unbonded amines. Here, a low-temperature synergistic strategy for both reconstructing and solidifying the perovskite top and buried interface is developed. By post-treating the 1,4-phenylenedimethanammonium (PDMA) based (PDMA)MA₄Pb₅I₁₆ films with cesium acetate (CsAc) before thermal annealing, a condensation reaction between R-COO^- and -NH₂ and ion exchange between Cs⁺ and MA⁺ occur. It converts the unbonded amines to amides and passivates uncoordinated Pb²⁺. Meanwhile, it adjusts film composition and improves the phase distribution without changing the out-of-plane grain orientation. Consequently, performance of 18.1% and much-enhanced stability (e.g., stability for photo-oxygen increased over 10 times, light-thermal for T₉₀ over 4 times, and reverse bias over 3 times) of (PDMA)MA₄Pb₅I₁₆ perovskite solar cells are demonstrated.