High-performance n-type PVDF/Ag2Se Free-standing Flexible Composite Thermoelectric Films Fabricated by Powder Hot-pressing

doi:10.15541/jim20250158

Abstract

Abstract:

Rapid development of applications in wearable devices, microelectronics, and internet of things has created an urgent demand for free-standing flexible thermoelectric films. Currently, research on n-type free-standing flexible thermoelectric films significantly lags behind, and there is an urgent need to enhance film performance through the optimization of preparation processes. In this study, high-performance n-type poly(vinylidene fluoride)/silver selenide (PVDF/Ag₂Se) free-standing flexible thermoelectric composite films were developed using a simple and efficient powder hot-pressing method. The high-temperature and high-pressure conditions during hot pressing induced recrystallization and grain growth of Ag₂Se, effectively reducing grain boundary density, significantly decreasing carrier scattering and interfacial resistance, thereby simultaneously enhancing carrier mobility, electrical conductivity and Seebeck coefficient. Meanwhile, the melted PVDF filled interstices of the Ag₂Se conductive network during hot pressing, substantially improving material flexibility while increasing density. Experimental results demonstrate that the hot-pressed sample with 80% (in mass) Ag₂Se exhibits outstanding room-temperature thermoelectric performance with an electrical conductivity of 277.0 S·cm^-1 and a Seebeck coefficient of -135 μV·K^-1, and thermoelectric power factor (PF) and estimated figure of merit (ZT) reach 509 μW·m^-1·K^-2 and 0.26, respectively. This performance not only significantly surpasses that of previously reported PVDF/Ag₂Se free-standing films but also ranks among the highest for all reported Ag₂Se-based organic/inorganic free-standing flexible thermoelectric films. Furthermore, mechanical tests reveal that the film maintains over 92% of its original conductivity after 500 bending cycles at a 5 mm radius, while exhibiting a maximum tensile strain four times greater than pure Ag₂Se films. This study provides a novel strategy for synergistic optimization of thermoelectric performance and mechanical flexibility in organic/inorganic composite thermoelectric materials.

Key words: silver selenide, composite thermoelectric film, free-standing, flexible, hot-pressing

CLC Number:

TB34

XU Zishuo, HU Yuejuan, HU Yuchen, CHEN Lidong, YAO Qin. High-performance n-type PVDF/Ag₂Se Free-standing Flexible Composite Thermoelectric Films Fabricated by Powder Hot-pressing[J]. Journal of Inorganic Materials, 2026, 41(4): 462-468.

Figures/Tables 10

Fig. 1 Schematic diagrams of preparation process for (a) Ag2Se nanowires and (b) PVDF/Ag2Se composite film

Fig. 2 (a) XRD pattern and (b) SEM image of Ag2Se nanowires

Fig. 3 XRD patterns of CP/HP-40% and 80% composite films

Fig. 4 (a) S, (b) σ and (c) PF of PVDF/Ag2Se cold/hot-pressed samples Colorful figures are available on website

Table 1 Typical thermoelectric performance of Ag2Se-based free-standing flexible composite films at room temperature (300 K)

Sample	Method	PF/(μW·m^-1·K^-2)	κ/(W·m^-1·K^-1)	ZT	Ref.
PVDF/Ag₂Se	Drip coating	281	-	-	[22]
PVDF/Ag₂Se	Suction filtration	189	7	0.0079	[24]
PVP/Ag₂Se	Silk screen	3.4	-	-	[29]
PVDF/PANI-coated Ag₂Se	Drip coating	196	-	-	[23]
BC/Ag₂Se	Suction filtration	386	0.41	0.22	[30]
Carbon/Ag₂Se	Silk screen	1761	0.66	0.81	[26]
PEDOT:PSS/Ag₂Se	Drip coating	327	-	-	[31]
PVDF/Ag₂Se	Hot pressing	509	0.59	0.26	This work

Fig. 5 (a-f) Surface and (g-i) cross-sectional SEM images of PVDF/Ag2Se composite and pure Ag2Se films (a) CP-60%; (b) CP-80%; (c) CP-Ag2Se; (d, g) HP-60%; (e, h) HP-80%; (f, i) HP-Ag2Se

Table 2 Carrier concentrations and mobilities of CP/HP-70% and 80% composite films

Sample	Carrier concentration/ (×10¹⁸, cm^-3)	Carrier mobility/ (cm²·V^-1·s^-1)
CP-70%	5.15	18
CP-80%	7.29	15
HP-70%	3.94	288
HP-80%	4.81	321

Fig. 6 Mechanical properties of HP-Ag2Se film and HP-80% composite film (a, b) Photographs of (a) HP-Ag2Se film and (b) HP-80% composite film before and after bending tests (around a 5 mm-radius cylinder); (c) Relative electrical conductivity (σ/σ0) of HP-80% composite film as a function of bending cycle; (d) Tensile stress-strain curves of HP-Ag2Se film and HP-80% composite film

Fig. S1 SEM image and corresponding EDS results of HP-80% composite film

Fig. S2 DSC curves of Ag2Se and Se

References 32

[1]	BASKARAN P, RAJASEKAR M. Recent progress in thermoelectric devices and applications. Chemical Engineering Journal, 2025, 506: 159929. DOI URL
[2]	MAO J, CHEN G, REN Z F. Thermoelectric cooling materials. Nature Materials, 2021, 20(4): 454. DOI PMID
[3]	BERETTA D, NEOPHYTOU N, HODGES J M, et al. Thermoelectrics: from history, a window to the future. Materials Science and Engineering: R: Reports, 2019, 138: 100501.
[4]	SHI X L, WANG L J, LYU W Y, et al. Advancing flexible thermoelectrics for integrated electronics. Chemical Society Reviews, 2024, 53(18): 9254. DOI URL
[5]	PEI J, CAI B W, ZHUANG H L, et al. Bi₂Te₃-based applied thermoelectric materials: research advances and new challenges. National Science Review, 2020, 7(12): 1856. DOI URL
[6]	SHARMA P K, SENGUTTUVAN T D, SHARMA V K, et al. Revisiting the thermoelectric properties of lead telluride. Materials Today Energy, 2021, 21: 100713. DOI URL
[7]	ABBASI M S, SULTANA R, AHMED I, et al. Contemporary advances in organic thermoelectric materials: fundamentals, properties, optimization strategies, and applications. Renewable and Sustainable Energy Reviews, 2024, 200: 114579. DOI URL
[8]	JIN P H, LI D J, IOCOZZIA J, et al. Hybrid organic-inorganic thermoelectric materials and devices. Angewandte Chemie International Edition, 2019, 58(43): 15206. DOI URL
[9]	ZHANG B T, SUN T T, WANG L J, et al. Inkjet printing preparation of AgCuTe thermoelectric thin films. Journal of Inorganic Materials, 2024, 39(12): 1325. DOI URL
[10]	DENG L H, LIU Y R, ZHANG Y Y, et al. Organic thermoelectric materials: niche harvester of thermal energy. Advanced Functional Materials, 2023, 33(3): 2210770. DOI URL
[11]	NANDIHALLI N, LIU C J, MORI T. Polymer based thermoelectric nanocomposite materials and devices: fabrication and characteristics. Nano Energy, 2020, 78: 105186. DOI URL
[12]	TRIPATHI A, LEE Y, LEE S, et al. Recent advances in n-type organic thermoelectric materials, dopants, and doping strategies. Journal of Materials Chemistry C, 2022, 10(16): 6114. DOI URL
[13]	LIU M, ZHANG X Y, ZHANG S X, et al. Ag₂Se as a tougher alternative to n-type Bi₂Te₃ thermoelectrics. Nature Communications, 2024, 15: 6580. DOI
[14]	ZHANG Z, SUN T T, WANG L J, et al. Flexible thermoelectric films with different Ag₂Se dimensions: performance optimization and device integration. Journal of Inorganic Materials, 2024, 39(11): 1221. DOI URL
[15]	LIU Y, ZHANG Q H, HUANG A B, et al. Fully inkjet-printed Ag₂Se flexible thermoelectric devices for sustainable power generation. Nature Communications, 2024, 15: 2141. DOI
[16]	LIU Y, LI J J, WANG Z X, et al. High thermoelectric performance of flexible Ag/Ag₂Se composite film on Nylon for low-grade energy harvesting. Journal of Materials Science & Technology, 2024, 179: 79.
[17]	YANG D, SHI X L, LI M, et al. Flexible power generators by Ag₂Se thin films with record-high thermoelectric performance. Nature Communications, 2024, 15: 923. DOI
[18]	PEREZ-TABORDA J A, CABALLERO-CALERO O, VERA- LONDONO L, et al. High thermoelectric zT in n-type silver selenide films at room temperature. Advanced Energy Materials, 2018, 8(8): 1702024. DOI URL
[19]	DU J J, ZHANG B T, JIANG M, et al. Inkjet printing flexible thermoelectric devices using metal chalcogenide nanowires. Advanced Functional Materials, 2023, 33(26): 2213564. DOI URL
[20]	ZHANG L, SHI X L, YANG Y L, et al. Flexible thermoelectric materials and devices: from materials to applications. Materials Today, 2021, 46: 62. DOI URL
[21]	AGHAYARI S. PVDF composite nanofibers applications. Heliyon, 2022, 8(11): e11620.
[22]	PARK D, JU H, KIM J. Enhanced thermoelectric properties of flexible N-type Ag₂Se nanowire/polyvinylidene fluoride composite films synthesized via solution mixing. Journal of Industrial and Engineering Chemistry, 2021, 93: 333. DOI URL
[23]	PARK D, KIM M, KIM J. High-performance PANI-coated Ag₂Se nanowire and PVDF thermoelectric composite film for flexible energy harvesting. Journal of Alloys and Compounds, 2021, 884: 161098. DOI URL
[24]	ZHOU H J, ZHANG Z J, SUN C X, et al. Biomimetic approach to facilitate the high filler content in free-standing and flexible thermoelectric polymer composite films based on PVDF and Ag₂Se nanowires. ACS Applied Materials & Interfaces, 2020, 12(46): 51506.
[25]	DING Y F, QIU Y, CAI K F, et al. High performance n-type Ag₂Se film on Nylon membrane for flexible thermoelectric power generator. Nature Communications, 2019, 10: 841. DOI
[26]	ZHANG M C, LI J J, LIU Y, et al. Screen printing high- performance free-standing Ag₂Se/carbon composite film for flexible thermoelectric converters. Nano Energy, 2025, 138: 110836. DOI URL
[27]	YUE Y C, LYU W Y, LIU W D, et al. Solvothermal synthesis of micro-pillar shaped Ag₂Se and its thermoelectric potential. Materials Today Chemistry, 2024, 39: 102183. DOI URL
[28]	LU Y, QIU Y, CAI K, et al. Ultrahigh performance PEDOT/Ag₂Se/CuAgSe composite film for wearable thermoelectric power generators. Materials Today Physics, 2020, 14: 100223. DOI URL
[29]	JIN Q, JIANG S, ZHAO Y, et al. Flexible layer-structured Bi₂Te₃ thermoelectric on a carbon nanotube scaffold. Nature Materials, 2019, 18: 62. DOI
[30]	LIU D, ZHAO Y X, YAN Z Q, et al. Screen-printed flexible thermoelectric device based on hybrid silver selenide/PVP composite films. Nanomaterials, 2021, 11(8): 2042. DOI URL
[31]	PALAPORN D, MONGKOLTHANARUK W, FAUNGNAWAKIJ K, et al. Flexible thermoelectric paper and its thermoelectric generator from bacterial cellulose/Ag₂Se nanocomposites. ACS Applied Energy Materials, 2022, 5(3): 3489. DOI URL
[32]	PARK D, KIM M, KIM J. Conductive PEDOT:PSS-based organic/inorganic flexible thermoelectric films and power generators. Polymers, 2021, 13(2): 210. DOI URL

High-performance n-type PVDF/Ag₂Se Free-standing Flexible Composite Thermoelectric Films Fabricated by Powder Hot-pressing

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