Ultra-thin Carbon Biphenylene Network as an Anisotropic Thermoelectric Material with High Temperature Stability Under Mechanical Strain

TL;DR

This study demonstrates that ultra-thin carbon biphenylene network (C-BPN) is a stable, anisotropic thermoelectric material at high temperatures, with tunable thermal and electrical properties under mechanical strain, suitable for nano-device applications.

Contribution

The paper introduces the thermoelectric properties of C-BPN, highlighting its anisotropic efficiency and strain-tunable thermal conductance, which are novel insights for nano-scale thermoelectric materials.

Findings

C-BPN exhibits significant directional anisotropy in transport properties.

Strain induces a metal-insulator transition, enhancing the Seebeck coefficient.

Power factor and figure of merit are improved through strain engineering.

Abstract

Carbon biphenylene network (C-BPN), which is an ultra-thin material consisting of carbon atoms arranged in square-hexagonal-octagonal (4-6-8) periodic rings, has intriguing properties for nano-scale device design due to its unique crystal structure. Here, using the Landauer formalism in combination with first-principles calculations, we show that C-BPN is a highly stable thermoelectric material at elevated temperatures under mechanical strain, where its thermoelectric efficiency can be anisotropically engineered. Transport calculations reveal that C-BPN's transmission spectrum has significant degrees of directional anisotropy and it undergoes a metal-insulator transition under strain, which leads to an increase in its Seebeck coefficient. C-BPN's lattice thermal conductance can be selectively tuned up to 35% bidirectionally at room temperature by strain engineering. Enhancement in its power factor and the suppression of its lattice thermal conductance improves the p-type figure of merit up to 0.31 and 0.76 at 300 and 1000~K, respectively. Our findings reveal that C-BPN has high potency to be used in thermoelectric nano devices with selective anisotropic properties at elevated temperatures.