Unraveling the Synergistic Role of Kinks in Zig-Zag Ag2Se Nanorod Arrays for High Room-Temperature zT and Improved Mechanical Properties: Experimental and First-Principles Studies

Abstract

Flexible thermoelectric materials are usually fabricated by incorporating conducting or organic polymers; however, it remains a formidable task to achieve high thermoelectric properties comparable to those of their inorganic counterparts. Here, we present a high zT value of 1.29 ± 0.31 at room temperature in the hierarchical zig-zag Ag₂Se nanorod arrays fabricated using the glancing angle deposition (GLAD) technique followed by a facile selenization process. The high zT value at 300 K is ascribed to the ultrahigh power factor of 3101 ± 252 μW/m-K² and the reduced thermal conductivity of 0.72 ± 0.01 W/mK. Based on ab initio computational and experimental evidence, we reveal that kinked Ag₂Se nanorod arrays consisting of rough interfaces modulate the lattice thermal conductivity up to 48.5% at room temperature. The modulation results from interchanging of phonon modes at kink points and enhanced scattering from a large number of rough interfaces. Further, benefiting from kinked hierarchy, a notable improvement in the mechanical performance is observed for zig-zag Ag₂Se nanorods which is confirmed by nanoindentation measurements. The synergic improvement in thermoelectric and mechanical performance not only unravels a paradigm to harness thermoelectric heat but also offers deeper insights into tuning the mechanical properties of inorganic thermoelectric materials.