Steric-Hindrance-Driven Shape Transition in PbS Quantum Dots: Understanding Size-Dependent Stability

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• 作者：Hyekyoung Choi ; Jae-Hyeon Ko ; Yong-Hyun Kim ; Sohee Jeong
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：April 10, 2013
• 年：2013
• 卷：135
• 期：14
• 页码：5278-5281
• 全文大小：286K
• 年卷期：v.135,no.14(April 10, 2013)
• ISSN：1520-5126

文摘

Ambient stability of colloidal nanocrystal quantum dots (QDs) is imperative for low-cost, high-efficiency QD photovoltaics. We synthesized air-stable, ultrasmall PbS QDs with diameter (D) down to 1.5 nm, and found an abrupt transition at D 鈮?4 nm in the air stability as the QD size was varied from 1.5 to 7.5 nm. X-ray photoemission spectroscopy measurements and density functional theory calculations reveal that the stability transition is closely associated with the shape transition of oleate-capped QDs from octahedron to cuboctahedron, driven by steric hindrance and thus size-dependent surface energy of oleate-passivated Pb-rich QD facets. This microscopic understanding of the surface chemistry on ultrasmall QDs, up to a few nanometers, should be very useful for precisely and accurately controlling physicochemical properties of colloidal QDs such as doping polarity, carrier mobility, air stability, and hot-carrier dynamics for solar cell applications.