2025 AIChE Annual Meeting

A Computational Study of Tunable Properties of the Two-Dimensional Material Sb2Te3 through Controlled Cr Doping: Insights for Next-Generation Thermoelectrics Design

Today, over 65% of global energy generation is lost as waste heat. Thermoelectric devices, a technology converting waste heat to electrical energy by harnessing temperature gradients, present the promising opportunity to recover this wasted energy for sustainable power generation. Among candidates for thermoelectric materials, two-dimensional van der Waals (vdW) materials such as transition metal dichalcogenides are especially promising, as their van der Waals gaps, held together by weak out-of-plane vdW interactions, facilitate controlled modulation of electronic, optical and mechanical properties.

A particular 2D vdW material of interest is Sb2Te3, a topological insulator with a characteristic quintuple-layered structure separated by vdW gaps, which has been shown experimentally to exhibit the quantum anomalous Hall effect enhancing thermoelectric performance. Despite being a leading room-temperature thermoelectric, its figure of merit remains below the threshold for viability. In this study, we use first-principles density functional theory calculations to reveal how chromium doping in Sb2Te3 enables unprecedented control over electronic properties enhancing thermoelectric performance.

Our findings show that Cr dopant atoms are thermodynamically favored to occupy sites buried within the quintuple layer as opposed to sites in the vdW gap. However, these buried sites have a higher associated energy barrier for Cr atoms to access as opposed to less thermodynamically favored sites within the vdW gap, in which the energy barrier is low enough to facilitate diffusion, but high enough to lock it in place, allowing for dopant control. This aligns with experimental observations that Cr atoms adopt sites within the vdW gap.

This doping provides an avenue for control of the electronic structure of Sb2Te3. Band-structure calculations show preservation of Sb2Te3’s semiconducting character with Cr doping in the vdW gap, whereas it shifts to a metallic character when Cr dopants are buried in the quintuple layers of Sb and Te. Calculations of the Seebeck coefficient, whose square is directly proportional to the thermoelectric figure of merit, show significant increases in Cr-doped Sb2Te3 compared to pristine Sb2Te3.

In summary, these results show stable and controlled Cr doping to be a powerful tool for tuning the electronic properties of van der Waals materials and enhancing thermoelectric performance, providing a blueprint for engineering thermoelectric properties of 2D vdW materials. Future directions include testing other dopants and 2D vdW hosts to create a “library” of host-guest interactions tailored to specific application: with vanadium dopants already showing similar promise in preliminary results. Experimental validation of thermoelectric improvement, and usage of machine-learned force fields are also important next steps for us.