A Solvothermal Synthetic Environmental Design for High-Performance SnSe-Based Thermoelectric Materials

SnSe is challenging to use in thermoelectric devices due to difficulties in simultaneously optimizing its thermoelectric and mechanical properties. Here, the authors show a unique solvothermal synthetic environmental design to fabricate super-large and micro/nanoporous Sn_0.965Se microplates by using CrCl₃. Cl⁻ ions to trigger Sn-vacancy formation and optimize the hole concentration to ≈3 × 10¹⁹ cm⁻³, while the as-formed Cr(OH)₃ colloidal precipitations act as “templates” to achieve micro/nanoporous features, leading to low lattice thermal conductivity of ≈0.2 W m⁻¹ K⁻¹ in the as-sintered polycrystal, contributing to a high ZT of ≈2.4 at 823 K and an average ZT of ≈1.1. Of particular note, the polycrystal exhibits high hardness (≈2.26 GPa) and compression strength (≈109 MPa), strengthened by grain refinement and vacancy-induced lattice distortions and dislocations; while a single-leg device provides a stable output power (>100 mW) and conversion efficiency of ≈10% by a temperature difference of 425 K, indicating great potential for applying to practical thermoelectric devices.