Wang Zhongyong, Singaravelu Arun Sundar S, Dai Rui, Nian Qiong, Chawla Nikhilesh, Wang Robert Y
School for Engineering of Matter, Transport & Energy, Arizona State University, Tempe, AZ, 85281, USA.
Angew Chem Int Ed Engl. 2020 Jun 8;59(24):9556-9563. doi: 10.1002/anie.201916760. Epub 2020 Apr 2.
The ongoing interest in colloidal nanocrystal solids for electronic and photonic devices necessitates that their thermal-transport properties be well understood because heat dissipation frequently limits performance in these devices. Unfortunately, colloidal nanocrystal solids generally possess very low thermal conductivities. This very low thermal conductivity primarily results from the weak van der Waals interaction between the ligands of adjacent nanocrystals. We overcome this thermal-transport bottleneck by crosslinking the ligands to exchange a weak van der Waals interaction with a strong covalent bond. We obtain thermal conductivities of up to 1.7 Wm K that exceed prior reported values by a factor of 4. This improvement is significant because the entire range of prior reported values themselves only span a factor of 4 (i.e., 0.1-0.4 Wm K ). We complement our thermal-conductivity measurements with mechanical nanoindentation measurements that demonstrate ligand crosslinking increases Young's modulus and sound velocity. This increase in sound velocity is a key bridge between mechanical and thermal properties because sound velocity and thermal conductivity are linearly proportional according to kinetic theory. Control experiments with non-crosslinkable ligands, as well as transport modeling, further confirm that ligand crosslinking boosts thermal transport.
对用于电子和光子器件的胶体纳米晶体固体的持续关注使得有必要深入了解它们的热传输特性，因为散热常常限制这些器件的性能。不幸的是，胶体纳米晶体固体通常具有非常低的热导率。这种极低的热导率主要源于相邻纳米晶体配体之间微弱的范德华相互作用。我们通过交联配体来克服这一热传输瓶颈，将弱的范德华相互作用转变为强的共价键。我们获得了高达1.7 Wm K的热导率，比先前报道的值高出4倍。这一改进意义重大，因为先前报道的所有值的范围本身仅跨越4倍（即0.1 - 0.4 Wm K）。我们用机械纳米压痕测量来补充热导率测量，结果表明配体交联提高了杨氏模量和声速。声速的增加是机械性能和热性能之间的关键桥梁，因为根据动力学理论，声速和热导率成正比。使用不可交联配体的对照实验以及传输模型进一步证实，配体交联促进了热传输。
