Key Takeaways & Executive Findings
- •• • InBr3 doping elevates carrier mobility to ~20.64 cm2 V−1 s−1 in n-type polycrystalline SnSe, a critical improvement for electrical conductivity and power factor. • • Lattice thermal conductivity is suppressed to ~0.25 W m−1 K−1 via multi-scale defects (dislocations and Br-rich nanowires), enhancing phonon scattering and thermal insulation. • • A peak ZT of ~1.41 at 823 K is achieved, representing a significant advancement for medium-temperature thermoelectric applications. • • An average ZT of ~0.42 over 323–823 K indicates stable performance across a wide temperature range, essential for practical device operation.
Abstract
SnSe is a promising thermoelectric material for medium-temperature applications due to its ultralow lattice thermal conductivity. However, the poor electrical conductivity of n-type polycrystalline SnSe significantly hinders its practical application. Here, we propose a dual-functional strategy employing InBr3 doping to synergistically enhance electrical transport while suppressing lattice thermal conductivity. For the first time, we demonstrate the successful construction of a Br-enriched conductive network within the SnSe matrix. The incorporation of In3+ and Br− introduces high-density charge carriers, while Br forms percolative conductive networks, resulting in a remarkable enhancement of carrier mobility to ~20.64 cm2 V−1 s−1. Simultaneously, the lattice thermal conductivity is substantially reduced to ~0.25 W m−1 K−1 through the formation of multi-scale defects, including dislocations and Br-rich nanowires, which effectively enhance phonon scattering. As a result, we achieve a peak figure of merit of ZT ~1.41 at 823 K, with an average figure of merit of ~0.42 over the temperature range of 323–823 K. This work provides a universal paradigm for decoupling electron-phonon interactions in thermoelectric materials, offering new insights for the optimization of thermoelectric performance.
1. Introduction
Thermoelectric materials enable direct conversion between heat and electricity, offering a route to recover waste heat and improve energy efficiency. The dimensionless figure of merit ZT = (σS²)T/κtot dictates performance, but the interdependence of electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (κtot) poses a fundamental challenge. Enhancing carrier mobility is a promising strategy to increase σ without degrading S, yet conventional doping often introduces scattering centers that limit mobility. In n-type polycrystalline SnSe, poor electrical conductivity has hindered practical application despite its ultralow lattice thermal conductivity.
This work addresses this bottleneck by employing InBr3 doping to create a Br-enriched conductive network within the SnSe matrix. The dual-functional strategy simultaneously enhances carrier mobility to ~20.64 cm2 V−1 s−1 and reduces lattice thermal conductivity to ~0.25 W m−1 K−1 through the formation of dislocations and Br-rich nanowires. This decoupling of electron and phonon transport yields a peak ZT of ~1.41 at 823 K, demonstrating a universal paradigm for optimizing thermoelectric performance in layered materials.
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Wenjie Li, Rui Zhang, Zeqing Hu, Jiahao Jiang, Zehao Lin, Min Ruan, Jingying Sun, Jing Shuai (2026). Achieving high thermoelectric performance in n-type polycrystalline SnSe via carrier mobility enhancement. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3750-6
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Frequently Asked Questions
What is the mechanism behind the enhanced carrier mobility in InBr3-doped SnSe?
The incorporation of In3+ and Br− introduces high-density charge carriers, while Br forms percolative conductive networks that provide efficient pathways for carrier transport, leading to a carrier mobility of ~20.64 cm2 V−1 s−1.
How does the lattice thermal conductivity reduction to ~0.25 W m−1 K−1 impact the thermoelectric figure of merit?
The reduction in lattice thermal conductivity, achieved through multi-scale defects such as dislocations and Br-rich nanowires, enhances phonon scattering, which directly increases ZT by lowering κtot. This contributes to the peak ZT of ~1.41 at 823 K.
What is the temperature range over which the average ZT of ~0.42 is maintained?
The average ZT of ~0.42 is maintained over the temperature range of 323–823 K, indicating stable thermoelectric performance across a wide operational window suitable for medium-temperature waste heat recovery.
How does the dual-functional InBr3 doping strategy compare to conventional doping approaches in terms of decoupling electron and phonon transport?
Unlike conventional doping that often trades off carrier mobility against carrier concentration, InBr3 doping simultaneously enhances carrier mobility and suppresses lattice thermal conductivity, achieving a peak ZT of ~1.41, which is a significant improvement over undoped n-type polycrystalline SnSe.
What are the potential scalability and cost implications of InBr3 doping for commercial thermoelectric devices?
InBr3 is a relatively inexpensive dopant, and the synthesis process is compatible with standard polycrystalline processing, suggesting potential for scalable production. The achieved high ZT and average ZT over a wide temperature range make this material attractive for medium-temperature power generation applications.
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