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Author: search.filters.author.Theekhasuk, NattharikaSubject: search.filters.subject.Bi2Te3

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    Dual optimization of ZT and output power in bulk Bi2Te3 through metal-assisted chemical etching
    (2026-03-01)
    Theekhasuk, Nattharika
    ;
    Sakulkalavek, Aparporn
    ;
    Ono, Takahito
    ;
    Sakdanuphab, Rachsak
    ;
    Nguyen, Duc Nam
    Thermoelectric materials offer a promising route for sustainable energy harvesting by directly converting waste heat into electricity, enabling compact, solid-state, and environmentally friendly energy solutions. Among them, bismuth telluride (Bi₂Te₃) stands out as the benchmark material for near-room-temperature applications due to its excellent electronic transport properties and commercial maturity. However, achieving high-performance in bulk or thick-film Bi₂Te₃ remains a formidable challenge. Conventional strategies such as doping, alloying, and nanoinclusion, while successful in thin films, often fail to translate effectively to bulk systems due to issues like pore collapse, poor uniformity, and degraded electrical connectivity. These limitations hinder the formation of efficient phonon-scattering architectures without compromising charge transport, resulting in limited improvement in the thermoelectric figure of merit (ZT). In this study, we present a novel and scalable nanoengineering strategy that applies metal-assisted chemical etching (MACE) to fabricate nanoporous surface layers on bulk Bi₂Te₃ for the first time. Unlike conventional nanostructuring techniques, MACE enables the formation of oriented nanostructures via a simple wet-chemical process, offering high tunability, low cost, and compatibility with large-area substrates. To reduce interfacial resistance, nickel was subsequently electrodeposited onto the nanostructured surface, forming a conformal contact layer that improves charge extraction and output performance. By systematically tuning the MACE duration, the optimized nanostructured Bi₂Te₃ sample exhibited a 2.3-fold improvement compared to the pristine bulk sample. Furthermore, due to the increased surface area from the nanoporous architecture, the internal resistance and output power of the nanostructured Bi₂Te₃ devices demonstrated 25-fold and 5.8-fold improvments, respectively, relative to the untreated sample. These remarkable improvements are attributed to the synergistic effect of enhanced phonon scattering within the nanoporous layer and improved charge transport enabled by the conformal nickel coating. This work not only introduces a powerful nanostructuring route for Bi₂Te₃ but also establishes a practical platform for high-performance, thick-film thermoelectric devices. The findings offer deep insight into the structure, property, and performance relationships governing thermoelectric efficiency and pave the way toward the scalable fabrication of next-generation thermoelectric modules for real-world applications such as industrial waste heat recovery and self-powered electronics.
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    Enhancing thermoelectric properties of Bi2Te3 film via CuI doping: Sputtering and solid iodination methods verified by ab initio calculation
    (2024-04-01)
    Khumtong, Tanakorn
    ;
    Theekhasuk, Nattharika
    ;
    Somdock, Nuttakrit
    ;
    Pluengphon, Prayoonsak
    ;
    Inceesungvorn, Burapat
    We have introduced an innovative method for preparing CuI-doped Bi<inf>2</inf>Te<inf>3</inf> films for the first time, which was also validated through ab initio calculations. The chemical reaction between the Cu-Bi<inf>2</inf>Te<inf>3</inf> film and iodine was conducted using the solid iodination method at room temperature. The results from X-ray diffraction and energy-dispersive spectrometry suggest that the sputtering process, followed by the solid iodination method, holds promise for synthesizing CuI-doped Bi<inf>2</inf>Te<inf>3</inf> films. Additionally, appropriately doping Bi<inf>2</inf>Te<inf>3</inf> with CuI enhances the (00l) crystal orientation, increases carrier concentration and mobility, resulting in improved electrical conductivity. Furthermore, our calculation results align with our experimental findings. An excess of substitutional CuI dopant tends to generate secondary phases, leading to alterations in the intrinsic conductivity and a reduction in the thermoelectric properties of Bi<inf>2</inf>Te<inf>3</inf>. Leveraging the enhanced electrical transport properties achieved through CuI doping, the maximum power factor of the (CuI)<inf>0.2</inf>Bi<inf>2</inf>Te<inf>2.9</inf> film reaches approximately 2.40 × 10<sup>−3</sup> W/mK<sup>2</sup> at 423 K, representing a 66 % enhancement compared to that of the Bi<inf>2</inf>Te<inf>2.9</inf> film, which has a power factor of 1.44 × 10<sup>−3</sup> W/mK<sup>2</sup>.