Defect Engineering Boosted Ultrahigh Thermoelectric Power Conversion Efficiency in Polycrystalline SnSe.

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Single-crystalline tin selenide (SnSe) exhibits excellent thermoelectric properties due to its 2D-layered structure, ultralow lattice thermal conductivity, and high figure of merit (zT).
• Achieving comparable performance in polycrystalline SnSe is crucial for technological applications but remains a significant challenge.

Purpose of the Study:

• To demonstrate a method for enhancing the thermoelectric performance of polycrystalline SnSe.
• To investigate the role of intrinsic defects in optimizing thermoelectric properties.
• To enable the practical implementation of high-performance thermoelectric generators.

Main Methods:

• Controlled alpha irradiation was used to optimize intrinsic defects in polycrystalline SnSe.
• Theoretical calculations, including defect formation energies and phonon dispersion studies, were performed.
• Experimental measurements of electrical conductivity and thermal conductivity were conducted.

Main Results:

• A high figure of merit (zT) of 2.4 was achieved at 800 K.
• Optimized intrinsic defects, specifically charged tin vacancies, enhanced the power factor to 0.9 mW/mK².
• Ultralow lattice thermal conductivity of 0.22 W/mK was achieved through vacancy-phonon scattering.

Conclusions:

• Intrinsic defect engineering via controlled irradiation is an effective strategy for boosting thermoelectric performance in polycrystalline SnSe.
• The developed approach of vacancy-phonon scattering significantly reduces thermal conductivity.
• This research facilitates the practical application of cost-effective, high-performance thermoelectric generators.