超低导热二维Ruddlesden-Pop相钙钛矿中相干声子输运的特征,ACS Nano

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超低导热二维Ruddlesden-Pop相钙钛矿中相干声子输运的特征
ACS Nano ( IF 15.8 ) Pub Date : 2021-03-04 , DOI: 10.1021/acsnano.0c03595
Alexander D. Christodoulides ₁ , Peijun Guo _{2,

3} , Lingyun Dai ₁ , Justin M. Hoffman ₄ , Xiaotong Li ₄ , Xiaobing Zuo ₅ , Daniel Rosenmann ₂ , Alexandra Brumberg ₄ , Mercouri G. Kanatzidis ₄ , Richard D. Schaller _{2,

4} , Jonathan A. Malen _{1,

6}

Affiliation

新兴的基于甲基铵碘化铅（MAPbI ₃）的Ruddlesden–Popper（RP）相钙钛矿，BA ₂ MA _{n –1} Pb _n I _{3 n +1}（n = 1–7），相对于环境条件显示出更高的稳定性达到MAPbI ₃，但在高温下仍会降解。我们通过实验确定n = 1-6时这些分层RP相的热导率，其中n定义每层重复的钙钛矿八面体的数量。我们测量n薄膜中的热导率分别为0.37±0.13 / 0.12、0.17±0.08 / 0.07、0.21±0.05 / 0.04和0.19±0.04 / 0.03 W / m·K在n = 3–6的单晶中，= 1–4和0.08±0.06 / 0.04、0.06±0.04 / 0.03、0.06±0.03 / 0.03和0.08±0.07 / 0.04 W / m·K 。除了n = 1以外，这些热导率均低于单晶MAPbI ₃报道的0.34–0.50 W / m·K范围。降序晶格动力学模型表明，在类似取向的钙钛矿中，随着n的增加，热导率的初始下降趋势可能是由于相干声子的传输特性引起的，该相干声子是从上层结构中出现的，不会在有机丁基铵链和钙钛矿的界面上发生散射。八面体。降低n中相干声子的群速度= 3–6是声子弥散中能带变平的结果，其主要原因是它们的超低热导率。在沉积的超晶格中已通过实验证明了对导热系数的类似影响，但从未在天然定义的材料（如RP相）中证明过。GIWAXS测量结果表明，相对于相同n的单晶，较高n RP相的薄膜的取向控制程度较低，因此具有明显提高的热导率。

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Signatures of Coherent Phonon Transport in Ultralow Thermal Conductivity Two-Dimensional Ruddlesden–Popper Phase Perovskites

An emerging class of methylammonium lead iodide (MAPbI₃)-based Ruddlesden–Popper (RP) phase perovskites, BA₂MA_n–1Pb_nI_3n+1 (n = 1–7), exhibit enhanced stability to environmental conditions relative to MAPbI₃, yet still degrade at elevated temperatures. We experimentally determine the thermal conductivities of these layered RP phases for n = 1–6, where n defines the number of repeated perovskite octahedra per layer. We measure thermal conductivities of 0.37 ± 0.13/0.12, 0.17 ± 0.08/0.07, 0.21 ± 0.05/0.04, and 0.19 ± 0.04/0.03 W/m·K in thin films of n = 1–4 and 0.08 ± 0.06/0.04, 0.06 ± 0.04/0.03, 0.06 ± 0.03/0.03, and 0.08 ± 0.07/0.04 W/m·K in single crystals of n = 3–6. With the exception of n = 1, these thermal conductivities are lower than the range of 0.34–0.50 W/m·K reported for single-crystal MAPbI₃. Reduced-order lattice dynamics modeling suggests that the initially decreasing trend of thermal conductivity in similarly oriented perovskites with increasing n may result from the transport properties of coherent phonons, emergent from the superstructure, that do not scatter at the interfaces of organic butylammonium chains and perovskite octahedra. Reduced group velocity of coherent phonons in n = 3–6, a consequence of band flattening in the phonon dispersion, is primarily responsible for their ultralow thermal conductivities. Similar effects on thermal conductivity have been experimentally demonstrated in deposited superlattices, but never in naturally defined materials such as RP phases. GIWAXS measurements reveal that higher n RP phase thin films are less orientationally controlled and therefore possess apparently elevated thermal conductivities relative to single crystals of the same n.

更新日期：2021-03-23

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