Metastable polymorphs of inorganic solids often possess material properties not present in the corresponding thermodynamic polymorphs, making them targets for the development of new functional materials. In contrast with isolating metastable bulk materials, syntheses of metastable polymorphs on the nanoscale are aided by fast non‐equilibrium reaction kinetics and the favorable thermodynamic influence of surface energies, giving rise to greater ease of access to metastable high‐temperature polymorphs and, in some cases, new polymorphs that do not exist in the bulk. The syntheses of metastable semiconductor nanocrystals are of interest for their potentially unique optoelectronic and physicochemical properties. However, in many material systems, synthesizing nanocrystalline products away from thermodynamic equilibrium in a predictable manner remains an outstanding challenge. This review outlines direct synthetic methodologies that have been developed to enable control over the nucleation and growth of metastable polymorphs of semiconductor nanocrystals by tailoring reaction conditions, precursor kinetics, ligand and surface effects, and other synthetic levers. The case studies reviewed herein expound on the direct syntheses of metastable ZnSe, Cu₂SnSe₃, CuInSe₂, Ag₂Se, and AgInSe₂ nanocrystals, and although there remain numerous examples of metastable nanocrystal syntheses outside of these metal chalcogenide systems, the concepts discussed are of general utility to the field of metastable nanocrystal syntheses as a whole. Explicit examples in which new functional properties are afforded by metastable polymorphs of the aforementioned material systems are presented within the context of applications for solar cells, photonics, and optical sensing. Finally, the factors that affect the kinetic persistence of metastable nanocrystalline polymorphs are discussed at length for these material systems.

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胶体半导体纳米晶体中的多态亚稳态

无机固体的亚稳态多晶型物通常具有在相应的热力学多晶型物中不存在的材料特性，使其成为开发新功能材料的目标。与隔离亚稳态块状材料相比，纳米级亚稳态多晶型物的合成是由快速的非平衡反应动力学和表面能的有利热力学影响所辅助，从而更容易获得亚稳态高温多晶型物，在某些情况下情况下，批量中不存在的新的多态。亚稳态半导体纳米晶体的合成因其潜在的独特光电子和物理化学特性而受到关注。但是，在许多材料系统中 以可预测的方式合成远离热力学平衡的纳米晶体产物仍然是一个巨大的挑战。这篇综述概述了直接合成方法，该方法已被开发以通过调整反应条件，前驱体动力学，配体和表面效应以及其他合成手段来控制半导体纳米晶体的亚稳态多晶型物的形核和生长。本文回顾的案例研究阐述了亚稳ZnSe，Cu的直接合成₂ SnSe ₃，CuInSe ₂，Ag ₂ Se和AgInSe ₂纳米晶体，尽管在这些金属硫族化物体系之外仍存在许多亚稳态纳米晶体合成的例子，但所讨论的概念对于整个亚稳态纳米晶体合成领域是通用的。在太阳能电池，光子学和光学传感的应用范围内，给出了通过上述材料系统的亚稳多晶型物提供新功能特性的具体示例。最后，针对这些材料系统详细讨论了影响亚稳态纳米晶多晶型物动力学持久性的因素。