Abstract
Flexible solar-thermoelectric generators hold great promise for efficient solar energy harvesting and power supply in wearable electronics. However, the achievement of strong photothermal and thermoelectric performance simultaneously within a single material remains a significant challenge. Here, we propose a fully integrated solar-thermoelectric generator that directly employs Ag2Se thermoelectric thin films as the light-absorbing terminal, combined with a bottom infrared-reflective layer and surface visible anti-reflective coating. This multilayer architecture enables solar-selective absorption and enhances the photothermal conversion efficiency of Ag2Se up to 87.6%, while demonstrating good generalizability to other narrow-bandgap thermoelectric films. The resulting ring-shaped flexible generator delivers a maximum temperature difference and power density of 19.6 K and 0.17 μW cm-2 under 1-sun irradiation and exhibits a stable peak output power of ~1 μW under prolonged outdoor sunlight. These results highlight an effective strategy for high-efficiency solar-thermoelectric generators design and broaden the application potential of narrow-bandgap thermoelectric thin films in photothermal energy conversion.
Data availability
The Source data generated in this study are provided in the Supplementary Information/Source Data file. Source data are provided with this paper.
References
Kraemer, D. et al. High-performance flat-panel solar thermoelectric generators with high thermal concentration. Nat. Mater. 10, 532–538 (2011).
Kraemer, D. et al. Concentrating solar thermoelectric generators with a peak efficiency of 7.4%. Nat. Energy 1, 1–8 (2016).
Kashyap, R. K. & Pillai, P. P. Plasmonic nanoparticles boost solar-to-electricity generation at ambient conditions. Nano Lett. 24, 5585–5592 (2024).
Mishra, B. R., Vossier, A., Revol I., Almuneau, G. & Vaillon, R. Insight into cooling requirements for thermophotovoltaic devices. Sol. Energy Mater. Sol Cells 296, 114023 (2026).
Piness-Sommer, M., Braun, A., Katz, E. A. & Gordon, J. M. Ultra-compact combustion-driven high-efficiency thermophotovoltaic generators. Sol. Energy Mater. Sol. Cells 157, 953–959 (2016).
Marques-Hueso, J. et al. Photonic Crystal-driven spectral concentration for upconversion photovoltaics. Adv. Opt. Mater. 3, 568–574 (2014).
Esmaielpour, H., Lombez, L., Giteau, M., Guillemoles, J. F. & Suchet, D. Impact of excitation energy on hot carrier properties in InGaAs multi-quantum well structure. Prog. Photovoltaics: Res. Appl. 30, 1354–1362 (2022).
Arnaoutakis, G. E. et al. Enhanced energy conversion of up-conversion solar cells by the integration of compound parabolic concentrating optics. Sol. Energy Mater. Sol. Cells 140, 217–223 (2015).
Yang, Z. -y et al. Ag2Se/nylon self-supporting composite films for wearable photo-thermoelectric generators with high output characteristics. J. Mater. Chem. A 10, 21080–21092 (2022).
Wu, Z. et al. High-performance floating thermoelectric generator for all-day power supply. Nano Energy 133, 110443 (2025).
Dai, X. et al. All-automated fabrication of freestanding and scalable photo-thermoelectric devices with high performance. Adv. Mater. 36, e2312570 (2024).
Li, K. et al. All-in-one single-piece flexible solar thermoelectric generator with scissored heat rectifying p-n modules. Nano Energy 93, 106789 (2022).
Jin, X. Z. et al. Ultraflexible PEDOT:PSS/helical carbon nanotubes film for all-in-one photothermoelectric conversion. ACS Appl Mater. Interfaces 14, 27083–27095 (2022).
Jurado, J. P. et al. Solar harvesting: a unique opportunity for organic thermoelectrics?. Adv. Energy Mater. 9, 1902385 (2019).
Kim, H. J., Kim, B., Auh, Y. & Kim, E. Conjugated organic photothermal films for spatiotemporal thermal engineering. Adv. Mater. 33, e2005940 (2021).
Vossier, A., Blandre, E. & Vaillon, R. Hybridising photovoltaics and thermoelectrics: A detailed-balance analysis. Sol. Energy Mater Sol Cells 289, 113636 (2025).
Beeri, O. et al. Hybrid photovoltaic-thermoelectric system for concentrated solar energy conversion: Experimental realization and modeling. J. Appl. Phys. 118, 115104 (2015).
Mao, J. et al. High Thermoelectric cooling performance of n-type Mg3Bi2-based materials. Science 365, 495–498 (2019).
Zhao, P. et al. Plasticity in single-crystalline Mg3Bi2 thermoelectric material. Nature 631, 777–782 (2024).
Jiang, F. et al. Prefer-oriented Ag2Se crystal for high-performance thermoelectric cooling. Adv. Funct. Mater. 35, 2415000 (2024).
Xu, S. et al. Interfacial bonding enhances thermoelectric cooling in 3D-printed materials. Science 387, 845–850 (2025).
Lin, S. et al. Revealing the promising near-room-temperature thermoelectric performance in Ag2Se single crystals. J. Materiom. 9, 754–761 (2023).
Hou, S. et al. Encapsulated Ag2Se-based flexible thermoelectric generator with remarkable performance. Mater. Today Phys. 38, 101276 (2023).
Ding, Y. et al. High performance n-type Ag2Se film on nylon membrane for flexible thermoelectric power generator. Nat. Commun. 10, 841 (2019).
Lei, Y. et al. Microstructurally tailored thin beta-Ag2Se films toward commercial flexible thermoelectrics. Adv. Mater. 34, 2104786 (2022).
Chen, W. et al. Flexible Ag2Se-based thin-film thermoelectrics for sustainable energy harvesting and cooling. Nat. Commun. 16, 7579 (2025).
Qin, J. et al. Versatile polymer-coated Ag2Se thermoelectric materials and devices for multi-scenario applications developed by direct-ink printing. Nat. Commun. 16, 8497 (2025).
Cao, T. et al. Advancing Ag2Se thin-film thermoelectrics via selenization-driven anisotropy control. Nat. Commun. 16, 1555 (2025).
Yang, D. et al. Flexible power generators by Ag2Se thin films with record-high thermoelectric performance. Nat. Commun. 15, 923 (2024).
Liu, Y. et al. Fully inkjet-printed Ag2Se flexible thermoelectric devices for sustainable power generation. Nat. Commun. 15, 2141 (2024).
Qin, J. et al. Modulating carrier transport by cross-dimensional compositing of Ag2Se/MXene for high-performance flexible thermoelectrics. J. Mater. Chem. A 12, 17586–17595 (2024).
Yang, Z. Y., Jin, X. Z., Huang, C. H., Lei, Y. Z. & Wang, Y. Constructing A/B-side heterogeneous asynchronous structure with Ag2Se layers and bushy-like PPy toward high-performance flexible photo-thermoelectric generators. ACS Appl Mater. Interfaces 14, 33370–33382 (2022).
Dalven, R. & Gill, R. Energy gap in β-Ag2Se. Phys. Rev. 159, 645–649 (1967).
Zhou, J. et al. Decipher the Wavelength and intensity using photothermoelectric detectors. ACS Appl Mater. Interfaces 16, 47923–47930 (2024).
Shi, W.-P. et al. A broadband self-powered and stable photothermoelectric detector based on Ag2Se/MWCNTs composite fabricated via screen printing. Microstructures 5, 2025081 (2025).
Guo, R. et al. Spray-coated Ag2Se thin films for high-performance photothermoelectric detectors. J. Alloys Compd 1036, 181736 (2025).
Zhao, Y. D. et al. Stretchable photothermal membrane of NIR-II charge-transfer cocrystal for wearable solar thermoelectric power generation. Sci. Adv. 9, eadh8917 (2023).
Liu, J. Z. et al. Large-area radiation-modulated thermoelectric fabrics for high-performance thermal management and electricity generation. Sci. Adv. 11, eadr2158 (2025).
Han, W. B. et al. Zebra-inspired stretchable, biodegradable radiation modulator for all-day sustainable energy harvesters. Sci. Adv. 9, eadf5883 (2023).
Li, Y. T. et al. Exceptionally high power factor Ag2Se/Se/polypyrrole composite films for flexible thermoelectric generators. Adv. Funct. Mater. 32, 2106902 (2022).
Knickerbocker, S. A. & Kulkarni, A. K. Calculation of the figure of merit for indium tin oxide films based on basic theory. J. Vac. Sci. Technol. A: Vac., Surf., Films 13, 1048–1052 (1995).
Hou, S. et al. High performance wearable thermoelectric generators using Ag2Se films with large carrier mobility. Nano Energy 87, 106223 (2021).
Kulkarni, A. K., Schulz, K. H., Lim, T. S. & Khan, M. Dependence of the sheet resistance of indium-tin-oxide thin films on grain size and grain orientation determined from X-ray diffraction techniques. Thin Solid Films 345, 273–277 (1999).
Lu, Y. et al. Ultrahigh performance PEDOT/Ag2Se/CuAgSe composite film for wearable thermoelectric power generators. Mater. Today Phys. 14, 100223 (2020).
Hou, S. et al. High-performance, thin-film thermoelectric generator with self-healing ability for body-heat harvesting. Cell Rep. Phys. Sci. 3, 101146 (2022).
Jiang, C. et al. Ultrahigh performance polyvinylpyrrolidone/Ag2Se composite thermoelectric film for flexible energy harvesting. Nano Energy 80, 105488 (2021).
Saeidi Javash, M. et al. Machine learning-assisted ultrafast flash sintering of high-performance and flexible silver-selenide thermoelectric devices. Energy Environ. Sci. 15, 5093–5104 (2022).
Wang, J. et al. High-performance photothermal conversion of narrow-bandgap Ti2O3 nanoparticles. Adv. Mater. 29, 1603730 (2017).
Xiong, Z. C. et al. Flexible fire-resistant photothermal paper comprising ultralong hydroxyapatite nanowires and carbon nanotubes for solar energy-driven water purification. Small 14, 1803387 (2018).
Li, Y. et al. General heterostructure strategy of photothermal materials for scalable solar-heating hydrogen production without the consumption of artificial energy. Nat. Commun. 13, 776 (2022).
Cao, F. et al. Enhanced thermal stability of W-Ni-Al2O3 cermet-based spectrally selective solar absorbers with tungsten infrared reflectors. Adv. Energy Mater. 5, 1401042 (2014).
V. Besteiro, L., Kong, X.-T., Wang, Z., Rosei, F. & Govorov, A. O. Plasmonic glasses and films based on alternative inexpensive materials for blocking infrared radiation. Nano Lett. 18, 3147–3156 (2018).
Minot, M. J. Single-layer, gradient refractive index antireflection films effective from 0.35 to 2.5 μ. J. Opt. Soc. Am. 66, 515–519 (1976).
Kim, B., Shin, H., Park, T., Lim, H. & Kim, E. NIR-sensitive poly(3,4-ethylenedioxyselenophene) derivatives for transparent photo-thermo-electric converters. Adv. Mater. 25, 5483–5489 (2013).
Tang, X.-H. et al. Achieving free-standing PEDOT:PSS solar generators with efficient all-in-one photothermoelectric conversion. ACS Appl. Mater. Interfaces 15, 23286–23298 (2023).
Liu, Y. et al. Strong interaction between plasmon and topological surface state in Bi2Se3/Cu2-xS nanowires for solar-driven photothermal applications. Sci. Adv. 11, eadt2884 (2025).
Zhang, Q. et al. Transparent power-generating windows based on solar-thermal-electric conversion. Adv. Energy Mater. 11, 2101213 (2021).
Zhou, Z., Song, Q., Huang, B., Feng, S. & Lu, C. Facile fabrication of densely packed Ti3C2 MXene/nanocellulose composite films for enhancing electromagnetic interference shielding and electro-photothermal performance. ACS Nano 15, 12405–12417 (2021).
Qian, Y. et al. A PEDOT:PSS/MXene-based actuator with self-powered sensing function by incorporating a photo-thermoelectric generator. RSC Adv. 13, 32722–32733 (2023).
Sun Q. et al Radiation-modulated origami-based thermoelectric generator for continuous solar energy harvesting. Adv. Funct. Mater. e18493 https://doi.org/10.1002/adfm.202518493.(2025).
Wang, K. et al. Melanin–perovskite composites for photothermal conversion. Adv. Energy Mater. 9, 1901753 (2019).
Cai, Y. et al. Photothermal conversion of Ti2O3 film for tuning terahertz waves. iScience 25, 103661 (2022).
Fan, X., Ding, Y., Liu, Y., Liang, J. & Chen, Y. Plasmonic Ti3C2Tx MXene enables highly efficient photothermal conversion for healable and transparent wearable device. ACS Nano 13, 8124–8134 (2019).
He, M. et al. A flexible photo-thermoelectric nanogenerator based on MoS2/PU photothermal layer for infrared light harvesting. Nano Energy 49, 588–595 (2018).
Yin, L. et al. Low-temperature sintering of Ag nanoparticles for high-performance thermoelectric module design. Nat. Energy 8, 665–674 (2023).
Acknowledgements
This work was funded by the National Natural Science Foundation of China (52572216 S.W, 5247219 F.C), the National Natural Science Foundation of China for Distinguished Young Scholars (52425108 Q.Z), the Science Research Project of Hebei Education Department (JZX2024008 S.W), the Hebei Province Yanzhao Golden Platform Talent Aggregation Plan Key Talent Project (B2025003002 S.H), the Guangdong Basic and Applied Basic Research Foundation (2024B1515040022 F.C). the Natural Science Foundation of Hubei Province (2025AFB208 Z.W), and the Research Project of Hubei Provincial Department of Education (B2024122 Z.W).
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S.H.: Writing-review & editing, Writing-original draft, Visualization, Investigation, Data curation, Conceptualization, Funding acquisition. J.W. and X.L.: Investigation, Data curation. Z.W.: Funding acquisition, Data curation. G.Z., B.L., M.L., M.Z., S.Q.: Data curation. Z.L.: Resources. F.C., Q.Z., S.W.: Writing-review & editing, Writing-original draft, Supervision, Resources, Project administration, Funding acquisition.
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Hou, S., Wang, J., Zhang, G. et al. An all-in-one Ag2Se-based flexible solar-thermoelectric generator with photothermal integration. Nat Commun (2026). https://doi.org/10.1038/s41467-026-69120-w
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DOI: https://doi.org/10.1038/s41467-026-69120-w
