Materials Science and Engineering Department, University of Utah, Salt Lake City, UT, United States of America.
Department of Physics, Kenyatta University, Nairobi, Kenya.
J Phys Condens Matter. 2023 Feb 17;35(15). doi: 10.1088/1361-648X/acb89e.
2D materials have attracted broad attention from researchers for their unique electronic properties, which may be been further enhanced by combining 2D layers into vertically stacked van der Waals heterostructures (vdWHs). Among the superlative properties of 2D systems, thermoelectric (TE) energy conversion promises to enable targeted energy conversion, localized thermal management, and thermal sensing. However, TE conversion efficiency remains limited by the inherent tradeoff between conductivity and thermopower. In this paper, we use first-principles calculation to study graphene-based vdWHs composed of graphene layers and hexagonal boron nitride (h-BN). We compute the electronic band structures of heterostructured systems using Quantum Espresso and their TE properties using BoltzTrap2. Our results have shown that stacking layers of these 2D materials opens a bandgap, increasing it with the number of h-BN interlayers, which significantly improves the power factor (PF). We predict a PF of ∼1.0 × 10W Km s for the vdWHs, nearly double compared to 5 × 10W Km s that we obtained for single-layer graphene. This study gives important information on the effect of stacking layers of 2D materials and points toward new avenues to optimize the TE properties of vdWHs.
2D 材料因其独特的电子特性而引起了研究人员的广泛关注，通过将 2D 层组合成垂直堆叠的范德华异质结构（vdWHs），其特性可能会进一步增强。在 2D 系统的卓越特性中，热电（TE）能量转换有望实现目标能量转换、局部热管理和热感测。然而，TE 转换效率仍然受到电导率和塞贝克系数之间固有权衡的限制。在本文中，我们使用第一性原理计算研究了由石墨烯层和六方氮化硼（h-BN）组成的基于石墨烯的 vdWHs。我们使用 Quantum Espresso 计算了异质结构系统的电子能带结构，并使用 BoltzTrap2 计算了它们的 TE 特性。我们的结果表明，堆叠这些 2D 材料的层会打开带隙，随着 h-BN 层间的数量增加，带隙会增加，这显著提高了功率因子（PF）。我们预测 vdWHs 的 PF 约为 1.0×10W Km s，比我们获得的单层石墨烯的 5×10W Km s 几乎增加了一倍。这项研究提供了关于堆叠 2D 材料层的影响的重要信息，并为优化 vdWHs 的 TE 特性指明了新的途径。
