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arXiv 2408.05946cond-mat.mtrl-scicond-mat.mes-hall
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二维手性钙钛矿中的激子扩散

Exciton diffusion in two-dimensional chiral perovskites

Sophia Terres, Lucas Scalon, Julius Brunner, Dominik Horneber, Johannes Dureth, Shiyu Huang, Takashi Taniguchi, Kenji Watanabe, Ana Flavia Nogueira, Sven Hoefli… 展开作者

Sophia Terres, Lucas Scalon, Julius Brunner, Dominik Horneber, Johannes Dureth, Shiyu Huang, Takashi Taniguchi, Kenji Watanabe, Ana Flavia Nogueira, Sven Hoefling, Sebastian Klembt, Yana Vaynzof, Alexey Chernikov

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AI总结：

本研究针对二维手性钙钛矿中激子迁移率尚不明确的问题，通过瞬态光致发光显微镜表征MBA₂PbI₄的激子传输，发现其室温扩散系数达2 cm²/s且存在两种传输机制，纯对映体钙钛矿扩散更快，为手性光电器件研发提供了依据。

摘要：

二维（2D）有机-无机杂化钙钛矿凭借其独特的结构设计与化学灵活性，已成为发光和光伏应用的通用平台。这类材料的性能很大程度上取决于无机卤化铅骨架的选择以及周围的有机层。近年来，将手性阳离子引入二维钙钛矿的研究因有望引入手性并调控手性光学响应，引发了广泛关注。重要的是，这些材料的光学性质由强束缚激子主导，这类激子同时也是能量传输的主要载流子。因此，从基础材料特性和光电子应用的角度来看，光注入激子的迁移率至关重要，但目前仍是一个悬而未决的问题。本文中，我们利用瞬态光致发光显微镜表征了二维手性钙钛矿甲基苄基碘化铅（MBA₂PbI₄）中的激子传播行为，揭示了其在室温下超过100纳米的密度依赖传输特性，扩散系数高达2 cm²/s。我们观察到两种截然不同的传输机制：初始阶段的快速扩散传播，以及随后的局域化过程。此外，研究发现与外消旋混合物相比，含纯对映体阳离子的钙钛矿表现出更快的激子扩散，这与材料组成对无序度的影响相关。总体而言，室温下高效激子扩散的观测结果凸显了二维手性钙钛矿在融合手性光学特性、强光-物质相互作用与高效能量传输方面的潜力。

英文摘要：

Two-dimensional (2D) organic-inorganic hybrid perovskites emerged as a versatile platform for light-emitting and photovol-taic applications due to their unique structural design and chemical flexibility. Their properties depend heavily on both the choice of the inorganic lead halide framework and the surrounding organic layers. Recently, the introduction of chiral cations into 2D perovskites has attracted major interest due to their potential for introducing chirality and tuning the chiro-optical response. Importantly, the optical properties in these materials are dominated by tightly bound excitons that also serve as primary carriers for the energy transport. The mobility of photoinjected excitons is thus important from the perspectives of fundamental material properties and optoelectronic applications, yet remains an open question. Here, we demonstrate exciton propagation in a 2D chiral perovskite methylbenzylammonium lead iodide (MBA2PbI4) using transient photoluminescence microscopy and reveal density-dependent transport over more than 100 nanometers at room temperature with diffusion coeffi-cients as high as 2 cm2/s. We observe two distinct regimes of initially rapid diffusive propagation and subsequent localiza-tion. Moreover, perovskites with enantiomer pure cations are found to exhibit faster exciton diffusion compared to the race-mic mixture, correlated with the impact of the material composition on disorder. Altogether, the observations of efficient exciton diffusion at room temperature highlight the potential of 2D chiral perovskites to merge chiro-optical properties with strong light-matter interaction and efficient energy transport.

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