The influence of non-idealities on the thermoelectric power factor of nanostructured superlattices

Abstract

Cross-plane superlattices composed of nanoscale layers of alternating potential wells and barriers have attracted great attention for their potential to provide thermoelectric power factor improvements and higher ZT figure of merit. Previous theoretical works have shown that the presence of optimized potential barriers could provide improvements to the Seebeck coefficient through carrier energy filtering, which improves the power factor by up to 40%. However, experimental corroboration of this prediction has been extremely scant. In this work, we employ quantum mechanical electronic transport simulations to outline the detrimental effects of random variation, imperfections and nonoptimal barrier shapes in a superlattice geometry on these predicted power factor improvements. Thus we aim to assess either the robustness or the fragility of these theoretical gains in the face of the types of variation one would find in real material systems. We show that these power factor improvements are relatively robust against: overly thick barriers, diffusion of barriers into the body of the wells, and random fluctuations in barrier spacing and width. However, notably, we discover that extremely thin barriers and random fluctuation in barrier heights by as little as 10% is sufficient to entirely destroy any power factor benefits of the optimized geometry. Our results could provide performance optimization routes for nanostructured thermoelectrics and elucidate the reasons why significant power factor improvements are not commonly realized in superlattices, despite theoretical predictions.

20 pages, 5 figures

References in corpus (3)

• Non-equilibrium Green's function treatment of phonon scattering in carbon nanotube transistors
• Optimizing Thermoelectric Power Factor by Means of a Potential Barrier
• Gated Si nanowires for large thermoelectric power factors

Cited by in corpus (8)

• On the Lorenz number of multi-band materials
• Hierarchical nanostructuring approaches for thermoelectric materials with high power factors
• On the effectiveness of the thermoelectric energy filtering mechanism in low-dimensional superlattices and nano-composites
• Hierarchically nanostructured thermoelectric materials: Challenges and opportunities for improved power factors
• Incoherent scattering can favorably influence energy filtering in nanostructured thermoelectrics
• Thermoelectric power factor of nanocomposite materials from two-dimensional quantum transport simulations
• Theoretical model for the Seebeck coefficient in superlattice materials with energy relaxation
• Thermoelectric power factor in nanostructured materials with randomized nanoinclusions