Nanostructured Sb₂Te₃ and Ag₂Te Films on Polyvinylidene Fluoride Membranes for Near-Room-Temperature Thermoelectric Heat Harvesting in Mechanically Flexible Devices

There is a great deal of interest in high figure-of-merit (ZT) thermoelectric materials for applications such as power generation from waste heat, solid-state refrigeration to support efficient photovoltaic conversion, and heat management in nanoelectronics. High room-temperature ZT in metal chalcogenides demonstrated through nanostructuring and doping have evinced interest in their integration with flexible substrates for powering consumer electronic devices^{1, 2}. Here, we demonstrate the integration of nanostructured thin films of Ag₂Te and Sb₂Te₃ nanostructures with polyvinylidene fluoride (PVDF) membranes for generating micro-volt-level electric fields. Ag₂Te nanowires and Sb₂Te₃nanoplatelets were obtained by either rapid microwave-stimulated surfactant-assisted synthesis or chemical conversion of Te nanowires without a surfactant. Both processes are efficient and amenable to scaled-up production. Micrometer-thick films of these layers were formed on PVDF by vacuum filtration, drying, and cold pressing. Both individual and bilayers of these materials remain mechanically resilient to flexing. The Ag₂Te-based device with Cu contacts generated ~2.3 mV from a human finger touch, and ~18 mV with a 50 K temperature gradient³, while devices with nanostructured Ag₂Te/Sb₂Te₃ bilayers exhibited ~2.5 mV, and ~28 mV, respectively. This talk will describe the key factors of materials synthesis and processing that play a defining role in the stability and performance of these flexible mV-harvesting devices. In particular, the roles of solvents, drying rate during film formation, size, and nanostructure shape will be discussed along with strategies to enhance mechanical flexibility and the thermoelectric properties. Our findings are relevant to scalable manufacturing of flexible thermoelectric devices for low-temperature energy harvesting. &lt;!--![endif]----&gt;<br/>&lt;!--[endif]----&gt;<br/><br/>1. Mehta, R. J.; Zhang, Y.; Karthik, C.; Singh, B.; Siegel, R. W.; Borca-Tasciuc, T.; Ramanath, G., A new class of doped nanobulk high-figure-of-merit thermoelectrics by scalable bottom-up assembly. <i>Nature Materials </i><b>2012,</b> <i>11</i> (3), 233-240.<br/>2. Mehta, R. J.; Zhang, Y.; Zhu, H.; Parker, D. S.; Belley, M.; Singh, D. J.; Ramprasad, R.; Borca-Tasciuc, T.; Ramanath, G., Seebeck and Figure of Merit Enhancement in Nanostructured Antimony Telluride by Antisite Defect Suppression through Sulfur Doping. <i>Nano Letters </i><b>2012,</b> <i>12</i> (9), 4523-4529.<br/>3. Kashyap, A.; Rawat, D.; Sarkar, D.; Singh, N. K.; Biswas, K.; Soni, A., Chemically Transformed Ag2Te Nanowires on Polyvinylidene Fluoride Membrane For Flexible Thermoelectric Applications. <i>Angewandte Chemie International Edition </i><b>2024,</b> <i>63</i> (11), e202401234.