Müller K-H
CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, New South Wales 2070, Australia.
J Chem Phys. 2008 Jul 28;129(4):044708. doi: 10.1063/1.2953462.
The room temperature thermoelectric properties of a three-dimensional array of molecular junctions are calculated. The array is composed of n-doped silicon nanoparticles where the surfaces are partially covered with polar molecules and the nanoparticles are bridged by trans-polyacetylene molecules. The role of the polar molecules is to reduce the band bending in the n-doped silicon nanoparticles and to shift the electronic resonances of the bridging molecules to the nanoparticle conduction band edges where the molecular resonances act as electron energy filters. The transmission coefficients of the bridging molecules that appear in the formulas for the Seebeck coefficient, the electrical conductance, and the electronic thermal conductance, are calculated using the nonequilibrium Green's function technique. A simple tight-binding Hamiltonian is used to describe the bridging molecules, and the self-energy term is calculated using the parabolic conduction band approximation. The dependencies of the thermoelectric properties of the molecular junctions on the silicon doping concentration and on the molecule-nanoparticle coupling are discussed. The maximal achievable thermoelectric figure of merit ZT of the array is estimated as a function of the phononic thermal conductance of the bridging molecules and the doping of the nanoparticles. The power factor of the array is also calculated. For sufficiently small phononic thermal conductances of the bridging molecules, very high ZT values are predicted.
计算了分子结三维阵列的室温热电性质。该阵列由n型掺杂硅纳米颗粒组成，其表面部分覆盖有极性分子，且纳米颗粒由反式聚乙炔分子桥接。极性分子的作用是减少n型掺杂硅纳米颗粒中的能带弯曲，并将桥接分子的电子共振转移到纳米颗粒导带边缘，在那里分子共振充当电子能量过滤器。利用非平衡格林函数技术计算了塞贝克系数、电导率和电子热导率公式中出现的桥接分子的传输系数。用一个简单的紧束缚哈密顿量来描述桥接分子，并使用抛物线导带近似计算自能项。讨论了分子结热电性质对硅掺杂浓度和分子-纳米颗粒耦合的依赖性。根据桥接分子的声子热导率和纳米颗粒的掺杂情况，估计了阵列可实现的最大热电优值ZT。还计算了阵列的功率因数。对于桥接分子足够小的声子热导率，预测会有非常高的ZT值。
