Contact effects on thermoelectric properties of textured graphene nanoribbons

TL;DR

This study investigates how contact effects influence the thermoelectric properties of textured graphene nanoribbons, revealing that tailored edge structures and contact design can optimize power output and efficiency.

Contribution

It introduces a theoretical framework for analyzing contact effects on thermoelectric performance of textured graphene nanoribbons, highlighting the advantages of zigzag configurations and defect insensitivity.

Findings

Textured ZGNRs exhibit higher power factors than AGNRs.

Defects in interior sites minimally affect power factor near band edges.

Optimized contact design can achieve up to 95% of the theoretical thermoelectric limit.

Abstract

Transport and thermoelectric properties of finite textured graphene nanoribbons (t-GNRs) connected to electrodes with various coupling strengths are theoretically studied in the framework of the tight-binding model and Green's function approach. Due to quantum constriction induced by the indented edges, such t-GNRs behave like serially-coupled graphene quantum dots (SGQDs). These types of SGQDs can be formed by tailoring zigzag GNRs (ZGNRs) or armchair GNRs (AGNRs). Their bandwidths and gaps can be engineered by varying the size of the quantum dot and the neck width at indented edges. Effects of defects and contact junction on electrical conductance, Seebeck coefficient and electron thermal conductance of t-GNRs are calculated. When a defect occurs in the interior site of textured ZGNRs (t-ZGNRs), the maximum power factor within the central gap or near the band edges is found to be insensitive to the defect scattering. Furthermore, we found that SGQDs formed by t-ZGNRs have significantly better electrical power outputs than those of textured ANGRs due to the improved functional shape of the transmission coefficient in t-ZGNRs. With a proper design of contact the maximum power factor ( figure of merit) of t-ZGNRs could reach $90\%$ ($95\%$) of the theoretical limit.