Assembling π‑Conjugated Molecules with Negative Gaussian Curvature for Efficient Carbon-Based Metal-Free Thermoelectric Material

The development of efficient, lightweight, cost-effective, and environmentally friendly thermoelectric materials is critical for energy conversion devices. However, none of the existing thermoelectric materials satisfy these requirements. Herein, we predict a novel carbon-based metal-free thermoelectric material denoted as bct-C80S16 that is composed of a π-conjugated saddle-shaped molecular unit with a negative Gaussian curvature, leading to a low lattice thermal conductivity while maintaining a high charge mobility. The resulting peak figure of merit (ZT) of 2.41 at 1000 K is much larger than those of conventional Bi- and Pb-based thermoelectric materials. Additionally, bct-C80S16 is highly porous and light, with a mass density of 1.11 g/cm3. Such a high thermoelectric performance and low mass density would make this metal-free semiconducting material promising for practical applications in space-based technologies.