School of Chemical Engineering , Nanjing University of Science and Technology , Nanjing , Jiangsu 210094 , China.
Department of Chemical and Biological Engineering , Iowa State University , Ames , Iowa 50011 , United States.
Nano Lett. 2018 Jun 13;18(6):4034-4039. doi: 10.1021/acs.nanolett.8b01691. Epub 2018 May 31.
Thermoelectricity offers a viable and reliable solution to convert waste heat into electricity. To enhance the performance and portability of thermoelectric materials, the crystal grain and pore structure should be simultaneously manipulated to achieve high electrical conductivity (σ), low thermal conductivity (κ), high figure of merit (zT), and low relative density. However, they cannot be synchronously realized using nanocrystals with uncontrolled domain size and shape as building blocks. Here, we employ solution-synthesized PbS nanocrystals with large grain size, controllable shape and tunable spatial packing to realize the aforementioned structural tuning. The as-sintered highly porous and well crystalline monolith exhibits high σ, low κ, high zT (1.06 at 838 K) and low relative density (82%). The phonon transport is studied by density functional theory highlighting the crucial role of phonon-pore scattering in reducing κ to enhance zT. Our strategy may benefit thermoelectrics and shed light on other technical fields such as catalysis, gas sensing, photovoltaics, and so forth.
热电提供了一种可行且可靠的解决方案，可以将废热转化为电能。为了提高热电材料的性能和便携性，应同时操纵晶体颗粒和孔结构，以实现高电导率 (σ)、低热导率 (κ)、高热导值 (zT) 和低相对密度。然而，使用具有不可控的域大小和形状的纳米晶体作为构建块，无法同时实现这些特性。在这里，我们采用溶液合成的 PbS 纳米晶体，其晶粒尺寸较大、形状可控且空间堆积可调，从而实现了上述结构调整。所得烧结的高多孔且结晶良好的整体结构表现出高 σ、低 κ、高热导值 (在 838 K 时为 1.06) 和低相对密度 (82%)。通过密度泛函理论研究了声子输运，突出了声子-孔散射在降低 κ 以提高 zT 方面的关键作用。我们的策略可能有益于热电领域，并为其他技术领域（如催化、气体传感、光伏等）提供启示。
