Dion-Jacobson (DJ) phase 2D perovskites have received wide attention due to their higher stability compared with 3D ones. However, some of the reported DJ 2D perovskites are not really robust, leading to a controversy over their stability. This necessitates clarification of the ambiguous stability mechanism. We herein elucidate that the stability of DJ 2D perovskites is determined by the rigidity of organic cations, which can induce co-adaptation of organic diammonium cations and inorganic [PbI₆]⁴⁻ octahedra to stabilize the 2D structure. By comparing three DJ 2D perovskites containing high-, medium-, and low-rigidity cations, we find that the medium-rigidity cation-based one presents higher structural stability. The finding is attributed to the appropriate cation rigidity, which enables organic diammoniums and inorganic octahedra to regulate their geometries to accommodate each other. This work explains the stability mechanism of DJ 2D perovskites and provides guidance for constructing highly stable candidates by adjusting the rigidity of organic cations.

Dion-Jacobson (DJ) 相 2D 钙钛矿由于与 3D 钙钛矿相比具有更高的稳定性而受到广泛关注。然而，一些报道的 DJ 2D 钙钛矿并不是真正坚固，导致了对其稳定性的争议。这就需要澄清模棱两可的稳定机制。我们在此阐明，DJ 2D 钙钛矿的稳定性取决于有机阳离子的刚性，这可以诱导有机二铵阳离子和无机 [PbI 6 ] ₄₋的^{共同适应。}八面体以稳定二维结构。通过比较三种含有高、中、低刚性阳离子的 DJ 2D 钙钛矿，我们发现中等刚性阳离子基钙钛矿具有更高的结构稳定性。这一发现归因于适当的阳离子刚性，这使得有机二铵和无机八面体能够调节它们的几何形状以相互适应。这项工作解释了 DJ 2D 钙钛矿的稳定性机制，并为通过调节有机阳离子的刚性构建高度稳定的候选材料提供了指导。