Thermal Stability of Semiconductor Nanocrystal Solids: Understanding Nanocrystal Sintering and Grain Growth
Thermal Stability of Semiconductor Nanocrystal Solids: Understanding Nanocrystal Sintering and Grain Growth
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DOI：
10.1021/acs.jpcc.2c07400
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发表时间：
2022-12
期刊：
影响因子：
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通讯作者：
Wenyong Liu;Vishwas Srivastava;J. Kurley;Cheng-yang Jiang;D. Talapin
中科院分区：
文献类型：
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作者：
Wenyong Liu;Vishwas Srivastava;J. Kurley;Cheng-yang Jiang;D. Talapin
纳米材料相对于大块固体是天然亚稳态的。这就提出了非常重要的基本问题，即它们的形态稳定性，特别是当纳米级微晶相互接触或几乎接触时，例如在薄膜器件中。在某些情况下，纳米结构化必须在操作条件下保持（例如，在量子点LED、激光器、光电探测器和纳米颗粒热电器件中）。在其他情况下，我们使用纳米晶体颗粒作为具有大晶粒的材料的前体，并旨在尽可能有效地烧结它们（例如，在多晶薄膜太阳能电池中）。我们进行了系统的研究，烧结和晶粒生长的材料组成的各种亚10纳米半导体晶粒。单个半导体晶粒之间的边界已经使用无机表面配体进行了化学工程。我们发现，纳米晶半导体的烧结和晶粒生长的早期阶段是由离子迁移率的表面，而晶粒生长的后期阶段是由晶界的迁移率控制。这似乎是半导体纳米晶体的普遍现象，它导致了几个有趣和违反直觉的趋势。例如，与II-VI CdSe纳米晶体相比，III-V InAs纳米晶体通常对烧结和晶粒生长更有弹性，即使体CdSe具有比InAs显著更高的熔点温度（1268 ° C对942 ° C）。当与固-固相变相结合时，晶粒生长可以显著加速。这些发现扩展了我们的工具箱，为不同的应用程序的合理设计的材料。
Nanomaterials are naturally metastable with respect to bulk solids. This raises the very important fundamental problem of their morphological stability, especially when nanoscale crystallites are touching or nearly touching each other, such as in thin-film devices. In some cases, nanostructuring must be preserved under operational conditions (e.g., in quantum dot LEDs, lasers, photodetectors, and nanogranular thermoelectric devices). In other cases, we use nanocrystalline particles as precursors to a material with large crystalline grains and aim to sinter them as efficiently as possible (e.g., in polycrystalline thin-film solar cells). We carried out a systematic study of sintering and grain growth in materials composed of various sub-10 nm semiconductor grains. The boundaries between individual semiconductor grains have been chemically engineered using inorganic surface ligands. We found that the early stages of sintering and grain growth of nanocrystalline semiconductors are controlled by the ion mobility at the nanocrystal surfaces, while the late stages of grain growth are controlled by the mobility of the grain boundaries. This appears to be a general phenomenon for semiconductor nanocrystals, and it leads to several interesting and counterintuitive trends. For example, III–V InAs nanocrystals are generally much more resilient against sintering and grain growth compared to II–VI CdSe nanocrystals even though bulk CdSe has significantly higher melting point temperature than InAs (1268 °C vs 942 °C). Grain growth can be dramatically accelerated when coupled to solid−solid phase transitions. These findings expand our toolbox for rational design of nanocrystal materials for different applications.