Flexible Polymer-Assisted Mesoscale Self-Assembly of Colloidal CsPbBr3 Perovskite Nanocrystals into Higher Order Superstructures with Strong Inter-Nanocrystal Electronic Coupling,Journal of the American Chemical Society

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Flexible Polymer-Assisted Mesoscale Self-Assembly of Colloidal CsPbBr3 Perovskite Nanocrystals into Higher Order Superstructures with Strong Inter-Nanocrystal Electronic Coupling
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2019-01-04 , DOI: 10.1021/jacs.8b10083
Yang Yang ₁ , Jacob T. Lee ₁ , Thakshila Liyanage ₁ , Rajesh Sardar _{1,

2}

Affiliation

Surface-passivating ligands, although ubiquitous to colloidal nanocrystal (NC) syntheses, play a role in assembling NCs into higher order structures and hierarchical superstructures, which has not been demonstrated yet for colloidal CsPbX3 (X = Cl, Br, and I) NCs. In this work, we report that functional poly(ethylene glycols) (PEG6-Y, Y = -COOH and -NH2) represent unique surface-passivating ligands enabling the synthesis of near-uniform CsPbBr3 NCs with diameters of 3.0 nm. The synthesized NCs are assembled into individual pearl necklaces, bundled pearl necklaces, lamellar, and nanorice superstructures, in situ. It is believed a variety of forces, including van der Waals attractions between hydrophilic PEG tails in a nonpolar solvent and dipole-dipole attraction between NCs, drive mesoscale assembly to form superstructures. Furthermore, postsynthetic ligand treatment strengthens the argument for polymer-assisted mesoscale assembly as pearl necklace assemblies can be successfully converted into either lamellar or nanorice structures. We observe an ∼240 meV bathochromic shift in the lowest energy absorption peak of CsPbBr3 NCs when they are present in the lamellar and nanorice assemblies, representing strong inter-NC electronic coupling. Moreover, pearl necklace structures are spontaneously assembled into micrometer length scale twisted ribbon hierarchical superstructures during storage of colloidal CsPbBr3 NCs. The results show that the self-assembled superstructures of CsPbBr3 NCs are now feasible to prepare via template-free synthesis, as self-assembled structures emerge in the bulk solvent, a process that mimics biological systems except for the use of nonbiological surface ligands (PEG6-Y). Taken together, emergent optoelectronic properties and higher order superstructures of CsPbBr3 NCs should aid their potential use in solid-state devices and simplify scalable manufacturing.

中文翻译：

柔性聚合物辅助中尺度胶体 CsPbBr3 钙钛矿纳米晶体自组装成具有强纳米晶体间电子耦合的高阶超结构

表面钝化配体虽然普遍存在于胶体纳米晶体 (NC) 合成中，但在将 NCs 组装成更高阶结构和分级超结构方面发挥作用，胶体 CsPbX3 (X = Cl、Br 和 I) NCs 尚未证明这一点。在这项工作中，我们报告了功能性聚（乙二醇）（PEG6-Y，Y = -COOH 和 -NH2）代表独特的表面钝化配体，能够合成直径为 3.0 nm 的近乎均匀的 CsPbBr3 NC。合成的 NCs 原位组装成单独的珍珠项链、捆绑珍珠项链、层状和纳米米上层结构。据信，多种力，包括非极性溶剂中亲水性 PEG 尾部之间的范德华吸引力和 NC 之间的偶极-偶极吸引力，驱动中尺度组装以形成超结构。此外，合成后配体处理加强了聚合物辅助中尺度组装的论点，因为珍珠项链组装可以成功转化为层状或纳米结构。当 CsPbBr3 NCs 存在于层状和纳米米组件中时，我们观察到 CsPbBr3 NCs 的最低能量吸收峰有 ~240 meV 红移，这代表了强的 NC 间电子耦合。此外，在胶体 CsPbBr3 NCs 的储存过程中，珍珠项链结构会自发组装成微米长度的扭曲带状分层上层结构。结果表明，CsPbBr3 NCs 的自组装超结构现在可以通过无模板合成制备，因为自组装结构出现在本体溶剂中，除了使用非生物表面配体 (PEG6-Y) 外，模拟生物系统的过程。总之，CsPbBr3 NCs 的新兴光电特性和更高阶的超结构应该有助于它们在固态设备中的潜在用途并简化可扩展制造。

更新日期：2019-01-04

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