Sn-Doping-Induced Biphasic Structure Advances Ductile Ag₂S-Based Thermoelectrics

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Silver sulfide (Ag2S) is a promising flexible thermoelectric material due to its ductility.
• Current methods to enhance Ag2S thermoelectric performance often reduce its flexibility.
• Efficient waste heat harvesting requires materials with both high thermoelectric performance and mechanical flexibility.

Purpose of the Study:

• To develop a novel Sn-doping strategy for Ag2S to simultaneously improve thermoelectric properties and retain ductility.
• To investigate the effect of Sn-doping induced biphasic structuring on electron and phonon transport.
• To fabricate and evaluate a flexible thermoelectric device based on the optimized material.

Main Methods:

• Incorporation of Sn-doping into Ag2S0.7Se0.3 to create a biphasic structure: (Ag, Sn)2S0.7Se0.3 and Ag2S0.7Se0.3.
• Characterization of the biphasic material's structural, electrical, and thermal transport properties.
• Fabrication of a four-leg in-plane flexible thermoelectric device.

Main Results:

• Achieved a figure-of-merit (ZT) of 0.42 at 343 K with over 90% ductility.
• Optimized power factor reached 5 µW cm⁻² K⁻² at 343 K due to enhanced carrier concentration and mobility.
• Suppressed lattice thermal conductivity to 0.18 W m⁻¹ K⁻¹ via biphasic structure-induced defects.
• Fabricated flexible device demonstrated a maximum power density of ≈49 µW cm⁻² at ΔT = 30 K.

Conclusions:

• Sn-doping induced biphasic structuring is an effective strategy for synergistic control of electron and phonon transport in Ag2S-based thermoelectrics.
• The developed material offers a superior combination of thermoelectric performance and mechanical flexibility compared to existing options.
• This advancement paves the way for efficient flexible thermoelectric devices for waste heat recovery applications.