Lee Seungjin, Choi Min-Jae, Sharma Geetu, Biondi Margherita, Chen Bin, Baek Se-Woong, Najarian Amin Morteza, Vafaie Maral, Wicks Joshua, Sagar Laxmi Kishore, Hoogland Sjoerd, de Arquer F Pelayo García, Voznyy Oleksandr, Sargent Edward H
Department of Electrical and Computer Engineering, University of Toronto, 35 St George Street, Toronto, ON, M5S 1A4, Canada.
Department of Chemical and Biochemical Engineering, Dongguk University, Seoul, 04620, Republic of Korea.
Nat Commun. 2020 Sep 23;11(1):4814. doi: 10.1038/s41467-020-18655-7.
Surface ligands enable control over the dispersibility of colloidal quantum dots (CQDs) via steric and electrostatic stabilization. Today's device-grade CQD inks have consistently relied on highly polar solvents: this enables facile single-step deposition of multi-hundred-nanometer-thick CQD films; but it prevents the realization of CQD film stacks made up of CQDs having different compositions, since polar solvents redisperse underlying films. Here we introduce aromatic ligands to achieve process-orthogonal CQD inks, and enable thereby multifunctional multilayer CQD solids. We explore the effect of the anchoring group of the aromatic ligand on the solubility of CQD inks in weakly-polar solvents, and find that a judicious selection of the anchoring group induces a dipole that provides additional CQD-solvent interactions. This enables colloidal stability without relying on bulky insulating ligands. We showcase the benefit of this ink as the hole transport layer in CQD optoelectronics, achieving an external quantum efficiency of 84% at 1210 nm.
表面配体能够通过空间位阻和静电稳定作用来控制胶体量子点（CQD）的分散性。如今的器件级CQD油墨一直依赖于高极性溶剂：这使得能够轻松地一步沉积数百纳米厚的CQD薄膜；但这阻碍了由具有不同组成的CQD构成的CQD薄膜堆叠的实现，因为极性溶剂会使下层薄膜重新分散。在这里，我们引入芳香族配体以实现工艺正交的CQD油墨，从而实现多功能多层CQD固体。我们研究了芳香族配体的锚定基团对CQD油墨在弱极性溶剂中溶解度的影响，发现对锚定基团的明智选择会诱导产生一个偶极，该偶极提供额外的CQD-溶剂相互作用。这使得在不依赖庞大绝缘配体的情况下实现胶体稳定性。我们展示了这种油墨作为CQD光电器件中空穴传输层的优势，在1210nm处实现了84%的外量子效率。
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