AI 中文总结
本研究结合原位偏压拉曼光谱与DFT计算，揭示二维卤化物钙钛矿中载流子与特定晶格振动的选择性电声耦合，发现氟化及样品结构有序性对声子响应的调控作用。
AI 中文摘要
电声耦合支配着卤化物钙钛矿中的电荷输运、载流子弛豫及极化子形成，但其在低维体系中的微观起源仍知之甚少。本研究将原位偏压依赖拉曼光谱与密度泛函理论（DFT）计算相结合，直接探测二维Ruddlesden-Popper钙钛矿(PEA)₂PbI₄及其氟化类似物(PEA-F)₂PbI₄中的载流子-晶格相互作用。施加电场时，两种体系均表现出模式选择性拉曼线宽展宽，且主要集中在100 cm⁻¹附近，其余声子模式基本不受影响，揭示了注入载流子与特定晶格振动间存在高度选择性耦合。DFT计算将这些模式识别为杂化有机-无机振动，涉及有机间隔基与对称Pb-I赤道拉伸的耦合运动，而非纯无机声子。氟化通过改变分子堆积、晶体对称性及有机-无机耦合从根本上重构了振动景观，导致声子态密度变化、声子寿命延长及载流子介导的晶格响应增强。值得注意的是，电偏压在薄膜与单晶中产生相反的声子寿命演化：薄膜中声子寿命降低约17%至22%，而单晶中则升高20%至26%。这些对比响应表明，结构有序性在决定二维卤化物钙钛矿的载流子-声子相互作用及声子弛豫路径中发挥着关键作用。
英文摘要
Electron phonon coupling governs charge transport, carrier relaxation, and polaron formation in halide perovskites, yet its microscopic origin in low dimensional systems remains poorly understood. Here, we combine operando, bias dependent Raman spectroscopy with density functional theory (DFT) calculations to directly probe carrier lattice interactions in two-dimensional Ruddlesden Popper perovskites,(PEA)$_2$PbI$_4$ and its fluorinated analogue, (PEA-F)$_2$PbI$_4$. Under applied electric fields, both systems exhibit mode-selective Raman linewidth broadening predominantly near 100 cm$^{-1}$, whereas other phonon modes remain largely unaffected, revealing highly selective coupling between injected carriers and specific lattice vibrations. DFT calculations identify these modes as hybrid organic inorganic vibrations involving coupled motion of the organic spacer and symmetric Pb I equatorial stretching, rather than purely inorganic phonons. Fluorination fundamentally reconstructs the vibrational landscape by modifying molecular packing, crystal symmetry, and organic inorganic coupling, resulting in changes to the phonon density of states, longer phonon lifetimes, and an enhanced carrier mediated lattice response. Notably, electrical bias produces opposite phonon lifetime evolution in thin films and single crystals: the phonon lifetime decreases by approximately 17 to 22% in thin films but increases 20 to 26% in single crystals. These contrasting responses demonstrate that structural order plays a fundamental role in determining carrier phonon interactions and phonon relaxation pathways in two-dimensional halide perovskites.
