Incorporating a 2D perovskite layer on top of a 3D perovskite is an effective approach to enhance the long-term stability of 3D perovskite-based optoelectronic devices. However, cation migration across the interface of 2D and 3D perovskites, particularly under light or heat exposure, can lead to interfacial reconstructions. We investigated the cation migration kinetics across the interface of 2D BA₂PbBr₄ and 3D MAPbBr₃ by physical pairing. We monitored changes in both perovskite layers by unpairing them to understand the migration of cations from one layer to the other. The 2D BA₂PbBr₄ film showed comparatively more changes than the 3D MAPbBr₃ layer, which is due to the faster migration of smaller MA⁺ cation toward the BA₂PbBr₄ film, while the larger BA⁺ cation migrates at a slower rate toward the MAPbBr₃ film. The activation energies of MA⁺ and BA⁺ cation migrations were found to be 63 and 138 kJ mol^–1, respectively. Migration of the MA⁺ cation transformed the 2D BA₂PbBr₄ (n = 1) film into the higher dimensional quasi-2D perovskites (n = 2 and 3), with a higher “n” more at the surface. We also proposed and demonstrated a strategy to prevent cation migration by introducing the ultrathin ALD alumina layer between 2D and 3D perovskites.

中文翻译：

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深入了解 2D/3D 钙钛矿界面的阳离子迁移动力学及其预防策略


在 3D 钙钛矿顶部加入 2D 钙钛矿层是增强 3D 钙钛矿光电器件长期稳定性的有效方法。然而，阳离子在 2D 和 3D 钙钛矿界面上的迁移，特别是在光或热暴露下，可能会导致界面重建。我们通过物理配对研究了 2D BA ₂ PbBr ₄ 和 3D MAPbBr ₃ 界面上的阳离子迁移动力学。我们通过取消配对来监测两个钙钛矿层的变化，以了解阳离子从一层到另一层的迁移。 2D BA ₂ PbBr ₄ 薄膜比 3D MAPbBr ₃ 层显示出更多的变化，这是由于较小的 MA ⁺ PbBr ₄ 薄膜迁移，而较大的 BA ⁺ 阳离子以较慢的速率向 MAPbBr ₃ 电影。 MA ⁺ 和 BA ⁺ 阳离子迁移的活化能分别为 63 和 138 kJ mol ^–1 。 MA ⁺ 阳离子的迁移将 2D BA ₂ PbBr ₄ (n = 1) 薄膜转化为更高维的准二维钙钛矿 (n = 2 和3），表面“n”越高。我们还提出并演示了一种通过在 2D 和 3D 钙钛矿之间引入超薄 ALD 氧化铝层来防止阳离子迁移的策略。