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Spectroscopic Comparison of Thermal Transport at Organic-Inorganic and Organic-Hybrid Interfaces Using CsPbBr3 and FAPbBr3 (FA = Formamidinium) Perovskite Nanocrystals.
Nano Letters ( IF 9.6 ) Pub Date : 2019-10-11 , DOI: 10.1021/acs.nanolett.9b03502 Benjamin T Diroll 1 , Arun Mannodi-Kanakkithodi 1 , Maria K Y Chan 1 , Richard D Schaller 1, 2
Nano Letters ( IF 9.6 ) Pub Date : 2019-10-11 , DOI: 10.1021/acs.nanolett.9b03502 Benjamin T Diroll 1 , Arun Mannodi-Kanakkithodi 1 , Maria K Y Chan 1 , Richard D Schaller 1, 2
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Thermal transport across interfaces depends on the matching of vibrational structure at the interface. This work examines the transfer of thermal excitation from an organic ligand coating to either all-inorganic cesium lead tribromide (CsPbBr3) nanocrystals or hybrid organic-inorganic formamidinium lead tribromide (FAPbBr3) nanocrystals using selective infrared optical excitation. These two semiconductors are directly compared because they (or similar semiconductors) are currently envisioned as strong candidates in many optoelectronic technologies and they differ due to the presence of an organic or inorganic cation, which introduces substantial differences in the phonon density of states in otherwise quite similar semiconductors. Infrared excitation of C-H vibrations of surface-bound ligands generates a temperature gradient between the organic ligand shell and nanocrystal core, which results in heat flow, measured by probing changes of the semiconductor band gap. Heat transfer to both perovskite compositions of comparable sizes is similar (25-30 ps), due to fast intramolecular vibrational relaxation and similar matching of low-energy phonons with the organic ligand, but FAPbBr3 samples show a slow bleaching kinetic on the order of 1 ns. This slow, heat-induced change in the semiconductor band gap is attributed not to interfacial heat transfer but instead to thermal equilibration between the organic and inorganic sublattices of FAPbBr3. Ab initio molecular dynamics simulations support the hypothesis that low-energy inorganic sublattice phonon modes are populated initially in the heat transfer process, with a slow thermal population of the higher-energy phonon modes associated primarily with the organic cation. Slow thermal equilibration of FAPbBr3 is likely to substantially impact the time-dependent response of optoelectronic devices that heat the semiconductor active layer and provide further evidence that the poor bulk thermal transport of hybrid perovskite materials extends to microscopic thermal processes.
中文翻译：
使用CsPbBr3和FAPbBr3（FA = Formamidinium）钙钛矿纳米晶体在有机-无机和有机混合界面上的热传递的光谱比较。
跨界面的热传输取决于界面处振动结构的匹配。这项工作研究了使用选择性红外光学激发将热激发从有机配体涂层转移到全无机三溴化铯铅（CsPbBr3）纳米晶体或杂化有机-无机甲ami三溴化铅（FAPbBr3）纳米晶体。之所以直接比较这两种半导体是因为它们（或类似的半导体）目前在许多光电技术中被认为是强候选，而且由于有机或无机阳离子的存在而有所不同，这会在其他情况下造成声子密度的显着差异。类似的半导体。表面结合的配体的CH振动的红外激发在有机配体壳和纳米晶核之间产生温度梯度，从而导致热流，该热流通过探测半导体带隙的变化来测量。由于分子内的快速振动弛豫以及低能声子与有机配体的相似匹配，两种尺寸相同的钙钛矿组合物的热传递相似（25-30 ps），但FAPbBr3样品的漂白动力学慢，约为1 ns。半导体带隙中这种缓慢的，由热引起的变化不是由于界面传热引起的，而是由于FAPbBr3的有机和无机亚晶格之间的热平衡引起的。从头算分子动力学模拟支持以下假设：低能的无机亚晶格声子模式最初在传热过程中填充，而高能声子模式的缓慢热填充主要与有机阳离子相关。FAPbBr3的缓慢热平衡可能会显着影响加热半导体活性层的光电子器件的时间依赖性响应，并提供进一步的证据表明杂化钙钛矿材料的较差的整体热传递会扩展到微观热过程。
更新日期：2019-10-12
中文翻译：
使用CsPbBr3和FAPbBr3（FA = Formamidinium）钙钛矿纳米晶体在有机-无机和有机混合界面上的热传递的光谱比较。
跨界面的热传输取决于界面处振动结构的匹配。这项工作研究了使用选择性红外光学激发将热激发从有机配体涂层转移到全无机三溴化铯铅（CsPbBr3）纳米晶体或杂化有机-无机甲ami三溴化铅（FAPbBr3）纳米晶体。之所以直接比较这两种半导体是因为它们（或类似的半导体）目前在许多光电技术中被认为是强候选，而且由于有机或无机阳离子的存在而有所不同，这会在其他情况下造成声子密度的显着差异。类似的半导体。表面结合的配体的CH振动的红外激发在有机配体壳和纳米晶核之间产生温度梯度，从而导致热流，该热流通过探测半导体带隙的变化来测量。由于分子内的快速振动弛豫以及低能声子与有机配体的相似匹配，两种尺寸相同的钙钛矿组合物的热传递相似（25-30 ps），但FAPbBr3样品的漂白动力学慢，约为1 ns。半导体带隙中这种缓慢的，由热引起的变化不是由于界面传热引起的，而是由于FAPbBr3的有机和无机亚晶格之间的热平衡引起的。从头算分子动力学模拟支持以下假设：低能的无机亚晶格声子模式最初在传热过程中填充，而高能声子模式的缓慢热填充主要与有机阳离子相关。FAPbBr3的缓慢热平衡可能会显着影响加热半导体活性层的光电子器件的时间依赖性响应，并提供进一步的证据表明杂化钙钛矿材料的较差的整体热传递会扩展到微观热过程。
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