Finite element analysis of scaling of silicon micro-thermoelectric generators to nanowire dimensions

Abstract

We report 2-D planar and rotational symmetric finite element simulations analyzing scaling effects on the performance of single crystal silicon thermoelectric generators, down to micro- and nano-wire leg dimensions and with realistic 170 μm tall metal contacts. A drift diffusion model with thermoelectric terms and temperature dependent material parameters is used to accurately model device performance. Efficiency and power density were extracted for a range of widths (W = 0.1 to 5000 μm), heights (H = 0.5 to 1000 μm), and temperature differences (T = 50 to 1350 K). The efficiency of the micro thermoelectric generators increases as the aspect ratio (height/width) increases. For the narrowest widths, the efficiency saturates at aspect ratios ∼100–1000 suggesting that nanowires, which are expected to have lower thermal conductivities than the bulk values used here, are viable candidates for future thermoelectric devices.