Two-dimensional (2D) organic–inorganic hybrid lead halide perovskites are promising semiconductors for optoelectronics, spintronics, and ferroelectrics due to their versatile structural and physical properties enabled by a variety of organic spacer cations. While previous research has focused on new spacer cations for templating 2D perovskite structures and influencing their properties, the intercalation of functional molecules within the organic layers has been less explored. Here, we demonstrate the intercalation of iodine within the organic sublattice as an effective tool to tune interlayer electronic interactions and stabilize 2D perovskite structures that would otherwise not form. We synthesized and determined the single-crystal structures of seven new iodine-intercalated 2D perovskites with varying spacer cations and inorganic compositions. The intercalated iodine bridges neighboring inorganic layers via halogen bonding with the apical iodides, leading to interlayer vibrational and electronic couplings. The iodine intercalation enhances the lattice rigidity, which decreases phonon–phonon scattering and exciton–phonon coupling. Adjusting the inorganic composition further tunes the electronic band structures, because iodine’s frontier orbitals contribute differently to the band edge states, leading to varied band alignments and photoluminescence quenching behaviors. Moreover, a decreased anisotropic emission polarization is observed after iodine intercalation due to the decreased in-plane confinement of the excitons. Our results demonstrate iodine intercalation as a powerful tool for tuning the structural and optoelectronic properties of 2D perovskites.

中文翻译：

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通过插层化学调整层间耦合和稳定 2D 钙钛矿晶格


二维 （2D） 有机-无机杂化卤化铅钙钛矿是光电子学、自旋电子学和铁电体的有前途的半导体，因为它们具有由各种有机间隔阳离子实现的多功能结构和物理特性。虽然以前的研究集中在用于模板化 2D 钙钛矿结构并影响其特性的新间隔阳离子上，但对有机层内功能分子的嵌入探索较少。在这里，我们证明了碘在有机亚晶格内的插层是调节层间电子相互作用和稳定原本不会形成的 2D 钙钛矿结构的有效工具。我们合成并确定了七种具有不同间隔阳离子和无机组成的新型碘嵌入 2D 钙钛矿的单晶结构。插层碘通过与顶端碘化物的卤素键合在相邻的无机层之间架桥，导致层间振动和电子耦合。碘嵌入增强了晶格刚度，从而减少了声子-声子散射和激子-声子耦合。调整无机成分会进一步调整电子能带结构，因为碘的前沿轨道对能带边缘状态的贡献不同，从而导致不同的能带排列和光致发光猝灭行为。此外，由于激子的面内限制减少，在碘嵌入后观察到各向异性发射极化减少。我们的结果表明，碘嵌入是调节 2D 钙钛矿结构和光电特性的有力工具。