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<p>High crystallographic symmetry is a key feature of many inorganic semiconductors and underpins their remarkable physical properties. By contrast, hybrid (organic and inorganic) crystals such as two-dimensional metal halide perovskites exhibit much lower crystal symmetry due to in-plane or out-of-plane octahedral distortions. Although they exhibit efficient photoinduced emission at room temperature, limited control over charge carrier transport remains a major challenge for optoelectronic applications. Here, inspired by three-dimensional cubic (α-phase) FAPbI<sub>3</sub> (FA, formamidinium), we developed FA-based layered two-dimensional perovskites using tailored cage cations, spacers and crystallization protocols. The compounds achieve near-maximal predicted symmetry, adopting a tetragonal P4/mmm space group without octahedral distortion. Among reported two-dimensional perovskites, these materials present short interlayer distances (4 Å) and lower optical bandgaps (1.7–1.8 eV). The absence of octahedral distortions results in an exciton diffusion length of 2.5 µm and a diffusivity of 4.4 cm<sup>2 </sup>s<sup>−1</sup>, both of which are an order of magnitude larger than those of previously reported two-dimensional perovskites and are on par with monolayer transition metal dichalcogenides.</p><p></p>

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Exciton diffusion beyond 2 μm enabled by maximum symmetry in two-dimensional perovskites

  • 期刊论文

  • 发表日期：

    2026年4月2日

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  • Jin Hou,
  • Jared Fletcher,
  • Siedah J. Hall,
  • Hao Zhang,
  • Marios Zacharias,
  • George Volonakis,
  • Claire Welton,
  • Stefan Zeiske,
  • Isaiah W. Gilley,
  • Donghoon Shin,
  • Faiz Mandani,
  • Isaac Metcalf,
  • Shuo Sun,
  • Bo Zhang,
  • Yinsheng Guo,
  • Bin Chen,
  • G. N. Manjunatha Reddy,
  • Claudine Katan,
  • Jacky Even,
  • Matthew Y. Sfeir,
  • Mercouri G. Kanatzidis,
  • Aditya D. Mohite

摘要

High crystallographic symmetry is a key feature of many inorganic semiconductors and underpins their remarkable physical properties. By contrast, hybrid (organic and inorganic) crystals such as two-dimensional metal halide perovskites exhibit much lower crystal symmetry due to in-plane or out-of-plane octahedral distortions. Although they exhibit efficient photoinduced emission at room temperature, limited control over charge carrier transport remains a major challenge for optoelectronic applications. Here, inspired by three-dimensional cubic (α-phase) FAPbI3 (FA, formamidinium), we developed FA-based layered two-dimensional perovskites using tailored cage cations, spacers and crystallization protocols. The compounds achieve near-maximal predicted symmetry, adopting a tetragonal P4/mmm space group without octahedral distortion. Among reported two-dimensional perovskites, these materials present short interlayer distances (4 Å) and lower optical bandgaps (1.7–1.8 eV). The absence of octahedral distortions results in an exciton diffusion length of 2.5 µm and a diffusivity of 4.4 cm2 s−1, both of which are an order of magnitude larger than those of previously reported two-dimensional perovskites and are on par with monolayer transition metal dichalcogenides.