This work carefully studied the transition from 3D perovskite to 2D perovskite. Our system includes single crystals (SCs) of MAPbBr3, which were dipped in a solution of barrier molecules. Three monoammonium cations and one di‐ammonium cation were studied. Absorbance and cathodoluminescence were used to follow the formation of low‐dimensional perovskite on the SC surface. Quantitative nuclear magnetic resonance and scanning electron microscopy assist in quantitatively tracking the exchange process. We followed the barrier molecules' concentration during the exchange process and their penetration depth into the 3D single crystal. The short aliphatic chain penetrates much farther into the crystal (ca. 450 mm) than the long aliphatic chain barrier molecule. In contrast, the process time is the opposite: the long aliphatic chain requires 5 days to achieve an equilibrium state compared with 15 days for the short aliphatic chain. Ab initio calculations indicate that the exchange process initiates due to the methylammonium vacancies on the surface, and the process is inhibited by the interactions between the ‐NH3 group and the PbBr2 planes. This work sheds light on the kinetics and thermodynamics of the transition from 3D to 2D perovskites, which is important for stabilizing the hybrid perovskites.

中文翻译：

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跟踪从三维单晶到二维钙钛矿的维度转变

这项工作仔细研究了从 3D 钙钛矿到 2D 钙钛矿的转变。我们的系统包括 MAPbBr3 单晶 (SC)，将其浸入屏障分子溶液中。研究了三种单铵阳离子和一种二铵阳离子。使用吸光度和阴极发光来追踪 SC 表面低维钙钛矿的形成。定量核磁共振和扫描电子显微镜有助于定量跟踪交换过程。我们跟踪了交换过程中势垒分子的浓度及其对 3D 单晶的渗透深度。短脂肪链比长脂肪链屏障分子更深入晶体（约 450 毫米）。相反，过程时间则相反：长脂肪链需要 5 天才能达到平衡状态，而短脂肪链则需要 15 天。从头计算表明，交换过程是由于表面上的甲基铵空位引发的，并且该过程受到-NH3基团和PbBr2平面之间的相互作用的抑制。这项工作揭示了从 3D 到 2D 钙钛矿转变的动力学和热力学，这对于稳定杂化钙钛矿非常重要。