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Tuning the thermoelectric performance of flexible copper selenide thin films through sputtering pressure and hybrid microwave annealing
(2025-10-10)
Khuncharoen, Wasan
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Theekhasuk, Nattharika
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Rudradawong, Chalermpol
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Voraud, Athorn
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Sakdanuphab, Rachsak
Flexible copper selenide (Cu₂₋ₓSe) thin films were deposited on polyimide substrates by direct current magnetron sputtering under varying pressures (0.8–4.0 × 10⁻² mbar) and subsequently annealed using hybrid microwave irradiation at 250 °C for 10–30 min. Increasing sputtering pressure raised the copper content (62.2–63.8 at%) and suppressed the formation of Cu₃Se₂ impurities. Hybrid microwave annealing promoted the transformation to stoichiometric β-Cu₂Se, removed oxide phases such as selenium dioxide and copper oxide, and improved crystallinity, as confirmed by x-ray diffraction and x-ray photoelectron spectroscopy. Field-emission scanning electron microscopy revealed microstructural densification at 10–20 min, whereas 30 min induced cracks and porosity that degraded transport properties. The optimized 20-minute annealed film achieved a peak power factor of 81.5 × 10⁻⁵ W/m·K² at 300 °C—over 130 times higher than that of the as-deposited film and comparable to other flexible Cu₂Se systems. Stability tests confirmed excellent retention after three months of ambient storage. These results establish sputtering pressure control and hybrid microwave annealing as scalable strategies for high-performance, stable Cu₂Se thermoelectric films.
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Optimizing fabrication processes for scalable production of flexible thermoelectric modules: A case study on self-powered IoT systems
(2025-09-01)
Gobpant, Jakrit
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Klongratog, Bhanupol
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Rudradawong, Chalermpol
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Sakdanuphab, Rachsak
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Limsuwan, Pichet
This study explores the optimization of fabrication processes for flexible thermoelectric generators (FTEGs) to enhance their performance and scalability for industrial applications, with a focus on integrating them into self-powered Internet of Things (IoT) systems. The research investigates the impact of silicone layer thickness and applied fabrication pressures on the mechanical stability, energy harvesting efficiency, and power output of FTEGs. Results demonstrate that reducing the thermal conductivity of the silicone filler and optimizing the fabrication pressure significantly improves the performance of FTE modules. The optimized FTEGs, featuring a series-parallel configuration, achieve a power density of 5.2 mW/cm² under a temperature difference of 50 °C, surpassing prior benchmarks. The developed system efficiently harvests waste heat, charges a battery, and powers an IoT module for real-time monitoring of temperature, humidity, and carbon monoxide levels. These findings highlight the potential of FTEGs as a sustainable solution for energy harvesting and self-powered industrial monitoring applications.
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Influence of Sputtering Power Density on the Thermoelectric and Mechanical Properties of Flexible Thermoelectric Antimony Telluride Films Deposited by DC Magnetron Sputtering
(2020-05-01)
Junlabhut, Prasopporn
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Nuthongkum, Pilaipon
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Sakdanuphab, Rachsak
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Harnwunggmoung, Adul
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Sakulkalavek, Aparporn
Antimony telluride (Sb<inf>2</inf>Te<inf>3</inf>) films were deposited on flexible polyimide substrates by DC magnetron sputtering technique using a 99.9% alloy Sb<inf>2</inf>Te<inf>3</inf> target. We measured structural, electrical, thermoelectric and mechanical properties with sputtering power density in the range 30–50 W. X-ray diffraction confirmed that all Sb<inf>2</inf>Te<inf>3</inf> films have high crystallinity with a significant preferential growth along the (015) plane. Surface morphologies were verified by scanning electron microscope: deposited film grain size increased with sputtering power density. The elemental composition was determined by energy dispersive x-ray spectroscopy. Electrical transport properties, carrier concentration, was measured by Hall effect measurement at room temperature. Electrical conductivity and Seebeck coefficient were simultaneously measured by a DC four-terminal method (ZEM-3). The power factor was strongly dominated by electrical conductivity, leading to a maximum of 1.95 mW/K2m with sputtering power 45 W at 300°C. The wettability test, based on the contact angle, evaluated surface energy and hydrophilicity. Nanoindentation was measured on a NHT2 CSM Instrument with diamond Berkovich indenter (B-P 31) at room temperature. The hardness and elastic modulus of deposited Sb<inf>2</inf>Te<inf>3</inf> films increased with the power density.
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Empirical modelling and optimization of pre-heat temperature and Ar flow rate using response surface methodology for stoichiometric Sb2Te3 thin films prepared by RF magnetron sputtering
(2017-01-01)
Khumtong, Tanakorn
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Sakulkalavek, Aparporn
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Sakdanuphab, Rachsak
In this work, a flexible antimony telluride thin film was deposited by RF magnetron sputtering. The response surface methodology based on central composite design was used to study the influence of the Ar flow rate (A) and the pre-heat temperature of the substrate (T) on the Te content (%Te). The %Te of the thin film tended to increase with an increase in both the Ar flow rate and the pre-heat temperature. Stoichiometric Sb<inf>2</inf>Te<inf>3</inf> thin films were obtained that agreed with the model equation of %Te = 59.22 + 0.070 A - 0.098 T + 5.580 × 10−4AT – 7.212 × 10−4A2 + 1.05 × 10−4 T2. Micro-strainand dislocation density were enhanced using high Ar flow rate and low pre-heat temperature. The dislocation density and stoichiometry contributed to the substantially enhanced Seebeck coefficient and electrical conductivity of the films, respectively. The temperature dependence of the power factor is strongly dominated by electrical conductivity, leading to the highest value for a stoichiometric film of 2.0 × 0−3 W/m.K2 at 250 °C. During process optimization, several conditions can be prepared by RF magnetron sputtering with an Sb<inf>2</inf>Te<inf>3</inf> target in order to obtain stoichiometric Sb<inf>2</inf>Te<inf>3</inf> films. However, the expected condition to obtain highest power factor was the highest Ar gas flow rate and the lowest pre-heat temperature.

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