Photobase-Triggered Formation of 3D Epitaxially Fused Quantum Dot Superlattices with High Uniformity and Low Bulk Defect Densities
Photobase-Triggered Formation of 3D Epitaxially Fused Quantum Dot Superlattices with High Uniformity and Low Bulk Defect Densities
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DOI：
10.1021/acsnano.1c11130
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发表时间：
2022-02-22
期刊：
影响因子：
17.1
通讯作者：
Law, Matt
中科院分区：
文献类型：
--
作者：
Qian, Caroline;Abelson, Alex;Law, Matt
高度有序外延熔融胶体量子点超晶格(EPI-SLS)有望将量子点尺寸可调的光物理特性与体相半导体的高效电荷传输特性结合起来。然而，目前的EPI-SL制备方法很粗糙，导致样品在结构和化学上不均匀，具有高度集中的扩展缺陷，这些缺陷使载流子局域化，阻止了电子微带的出现。由于对导致未融合母体SL的外延-SL转化的配体化学了解不足，所需的制造改进受到阻碍。在这里，我们证明了在漂浮的量子点膜下将胺注入乙二醇亚相中的传统方法是通过胺使乙二醇去质子化以及随后油酸与量子点表面的糖氧化物交换而形成的。通过用氢氧离子取代胺，我们证明了任何产生足够剂量的糖氧化物的Bronsted-Lowry碱都可以产生epi-SL。然后，我们介绍了一种EPI-SL制作方法，它用溶解的光基的非接触式和均匀的照明来取代基极的点注入。多层膜(3D)的定量图谱显示，我们的光基制备的EPI-SLS在化学和结构上是均匀的，并且与胺点注入产生的高度不均匀和富含缺陷的EPI-SLS相比，体缺陷的浓度要低得多。光化学结构的均匀性和结构的完美性使其成为在自组装介观固体中实现微带电荷输运的主要候选材料。
Highly ordered epitaxially fused colloidal quantum dot (QD) superlattices (epi-SLs) promise to combine the size-tunable photophysics of QDs with the efficient charge transport of bulk semiconductors. However, current epi-SL fabrication methods are crude and result in structurally and chemically inhomogeneous samples with high concentrations of extended defects that localize carriers and prevent the emergence of electronic mini-bands. Needed fabrication improvements are hampered by inadequate understanding of the ligand chemistry that causes epi-SL conversion from the unfused parent SL. Here we show that epi-SL formation by the conventional method of amine injection into an ethylene glycol subphase under a floating QD film occurs by deprotonation of glycol by the amine and subsequent exchange of oleate by glycoxide on the QD surface. By replacing the amine with hydroxide ion, we demonstrate that any Bronsted-Lowry base that creates a sufficient dose of glycoxide can produce the epi-SL. We then introduce an epi-SL fabrication method that replaces point injection of a base with contactless and uniform illumination of a dissolved photobase. Quantitative mapping of multilayer (3D) films shows that our photobase-made epi-SLs are chemically and structurally uniform and have much lower concentrations of bulk defects compared to the highly inhomogeneous and defect-rich epi-SLs produced by amine point injection. The structural-chemical uniformity and structural perfection of photobase-made epi-SLs make them leading candidates for achieving emergent mini-band charge transport in a self-assembled mesoscale solid.