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Nanogap near-field thermophotovoltaics


Conversion of heat to electricity via solid-state devices is of great interest and has led to intense research of thermoelectric materials1,2. Alternative approaches for solid-state heat-to-electricity conversion include thermophotovoltaic (TPV) systems where photons from a hot emitter traverse a vacuum gap and are absorbed by a photovoltaic (PV) cell to generate electrical power. In principle, such systems may also achieve higher efficiencies and offer more versatility in use. However, the typical temperature of the hot emitter remains too low (<1,000 K) to achieve a sufficient photon flux to the PV cell, limiting practical applications. Theoretical proposals3,4,5,6,7,8,9,10,11,12 suggest that near-field (NF) effects13,14,15,16,17,18 that arise in nanoscale gaps may be leveraged to increase the photon flux to the PV cell and significantly enhance the power output. Here, we describe functional NFTPV devices consisting of a microfabricated system and a custom-built nanopositioner and demonstrate an ~40-fold enhancement in the power output at nominally 60 nm gaps relative to the far field. We systematically characterize this enhancement over a range of gap sizes and emitter temperatures, and for PV cells with two different bandgap energies. We anticipate that this technology, once optimized, will be viable for waste heat recovery applications.

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Fig. 1: Microscale devices for demonstration of near-field thermophotovoltaic energy conversion.
Fig. 2: Thermophotovoltaic measurement procedure.
Fig. 3: Thermophotovoltaic performance enhancement in the near field.
Fig. 4: Near-field thermophotovoltaic measurement with 0.303-eV-bandgap cell.


  1. 1.

    He, J. & Tritt, T. M. Advances in thermoelectric materials research: looking back and moving forward. Science 357, 1369–1377 (2017).

    Google Scholar 

  2. 2.

    Snyder, G. J. & Toberer, E. S. Complex thermoelectric materials. Nat. Mater. 7, 105–114 (2008).

    Article  Google Scholar 

  3. 3.

    Whale, M. D. & Cravalho, E. G. Modeling and performance of microscale thermophotovoltaic energy conversion devices. IEEE Trans. Energy Conver. 17, 130–142 (2002).

    Article  Google Scholar 

  4. 4.

    Narayanaswamy, A. & Chen, G. Surface modes for near field thermophotovoltaics. Appl. Phys. Lett. 82, 3544–3546 (2003).

    Article  Google Scholar 

  5. 5.

    Laroche, M., Carminati, R. & Greffet, J. J. Near-field thermophotovoltaic energy conversion. J. Appl. Phys. 100, 063704 (2006).

    Article  Google Scholar 

  6. 6.

    Basu, S., Chen, Y. B. & Zhang, Z. M. Microscale radiation in thermophotovoltaic devices—a review. Int. J. Energ. Res. 31, 689–716 (2007).

    Article  Google Scholar 

  7. 7.

    Park, K., Basu, S., King, W. P. & Zhang, Z. M. Performance analysis of near-field thermophotovoltaic devices considering absorption distribution. J. Quant. Spectrosc. Rad. 109, 305–316 (2008).

    Article  Google Scholar 

  8. 8.

    Bright, T. J., Wang, L. P. & Zhang, Z. M. Performance of near-field thermophotovoltaic cells enhanced with a backside reflector. J. Heat Transfer 136, 062701 (2014).

    Article  Google Scholar 

  9. 9.

    Tong, J. K., Hsu, W. C., Huang, Y., Boriskina, S. V. & Chen, G. Thin-film ‘thermal well’ emitters and absorbers for high-efficiency thermophotovoltaics. Sci. Rep. 5, 10661 (2015).

    Article  Google Scholar 

  10. 10.

    Chen, K. F., Santhanam, P. & Fan, S. H. Suppressing sub-bandgap phonon-polariton heat transfer in near-field thermophotovoltaic devices for waste heat recovery. Appl. Phys. Lett. 107, 091106 (2015).

    Article  Google Scholar 

  11. 11.

    Lau, J. Z. J. & Wong, B. T. Thermal energy conversion using near-field thermophotovoltaic device composed of a thin-film tungsten radiator and a thin-film silicon cell. J. Appl. Phys. 122, 084302 (2017).

    Article  Google Scholar 

  12. 12.

    Zhao, B. et al. High-performance near-field thermophotovoltaics for waste heat recovery. Nano Energy 41, 344–350 (2017).

    Article  Google Scholar 

  13. 13.

    Polder, D. & Van Hove, M. Theory of radiative heat transfer between closely spaced bodies. Phys. Rev. B 4, 3303–3314 (1971).

    Article  Google Scholar 

  14. 14.

    Pendry, J. B. Radiative exchange of heat between nanostructures. J. Phys. Condens. Matter 11, 6621–6633 (1999).

    Article  Google Scholar 

  15. 15.

    Joulain, K., Mulet, J. P., Marquier, F., Carminati, R. & Greffet, J. J. Surface electromagnetic waves thermally excited: radiative heat transfer, coherence properties and Casimir forces revisited in the near field. Surf. Sci. Rep. 57, 59–112 (2005).

    Article  Google Scholar 

  16. 16.

    Basu, S., Zhang, Z. M. & Fu, C. J. Review of near-field thermal radiation and its application to energy conversion. Int. J. Energ. Res. 33, 1203–1232 (2009).

    Article  Google Scholar 

  17. 17.

    Song, B., Fiorino, A., Meyhofer, E. & Reddy, P. Near-field radiative thermal transport: from theory to experiment. AIP Adv. 5, 053503 (2015).

    Article  Google Scholar 

  18. 18.

    Molesky, S. & Jacob, Z. Ideal near-field thermophotovoltaic cells. Phys. Rev. B 91, 205435 (2015).

    Article  Google Scholar 

  19. 19.

    Modest, M. F. Radiative Heat Transfer 3rd edn (Academic Press, Oxford, UK, 2013).

    Google Scholar 

  20. 20.

    Song, B. et al. Radiative heat conductances between dielectric and metallic parallel plates with nanoscale gaps. Nat. Nanotech. 11, 509–514 (2016).

    Article  Google Scholar 

  21. 21.

    DiMatteo, R. S. et al. Enhanced photogeneration of carriers in a semiconductor via coupling across a nonisothermal nanoscale vacuum gap. Appl. Phys. Lett. 79, 1894–1896 (2001).

    Article  Google Scholar 

  22. 22.

    DiMatteo, R. et al. Micron-gap ThermoPhotoVoltaics (MTPV). AIP Conf. Proc. 738, 42–51 (2004).

    Article  Google Scholar 

  23. 23.

    Ganjeh, Y. et al. A platform to parallelize planar surfaces and control their spatial separation with nanometer resolution. Rev. Sci. Instrum. 83, 105101 (2012).

    Article  Google Scholar 

  24. 24.

    Song, B. et al. Enhancement of near-field radiative heat transfer using polar dielectric thin films. Nat. Nanotech. 10, 253–258 (2015).

    Article  Google Scholar 

  25. 25.

    Whittaker, D. M. & Culshaw, I. S. Scattering-matrix treatment of patterned multilayer photonic structures. Phys. Rev. B 60, 2610–2618 (1999).

    Article  Google Scholar 

  26. 26.

    Yeh, P. Optical Waves in Layered Media (Wiley, New York, 1988).

    Google Scholar 

  27. 27.

    Francoeur, M., Menguc, M. P. & Vaillon, R. Solution of near-field thermal radiation in one-dimensional layered media using dyadic Green’s functions and the scattering matrix method. J. Quant. Spectrosc. Rad. 110, 2002–2018 (2009).

    Article  Google Scholar 

  28. 28.

    Zhu, L. & Fan, S. Near-complete violation of detailed balance in thermal radiation. Phys. Rev. B 90, 220301 (2014).

    Article  Google Scholar 

  29. 29.

    St-Gelais, R., Zhu, L., Fan, S. & Lipson, M. Near-field radiative heat transfer between parallel structures in the deep subwavelength regime. Nat. Nanotech. 11, 515–519 (2016).

    Article  Google Scholar 

  30. 30.

    Lenert, A. et al. A nanophotonic solar thermophotovoltaic device. Nat. Nanotech. 9, 126–130 (2014).

    Article  Google Scholar 

  31. 31.

    Guler, U., Boltasseva, A. & Shalaev, V. M. Refractory plasmonics. Science 344, 263–264 (2014).

    Article  Google Scholar 

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P.R. and E.M. acknowledge support from the Army Research Office under awards W911NF-16-1-0195 and W911NF-18-1-0004 (nanopositing and instrumentation), from the Department of Energy-Basic Energy Science under award DE-SC0004871 (scanning probes and experimental design) and the National Science Foundation under award CBET 1509691 (computational modelling). We acknowledge the Lurie Nanofabrication Facility for facilitating the fabrication of devices.

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P.R. and E.M. conceived and supervised the work. A.F. and L.Z. performed the experiments and calculations, and D.T. and R.M. fabricated the emitter devices. The manuscript was written by A.F., P.R. and E.M. with comments and input from all authors.

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Correspondence to Pramod Reddy or Edgar Meyhofer.

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The authors declare no competing interests.

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Fiorino, A., Zhu, L., Thompson, D. et al. Nanogap near-field thermophotovoltaics. Nature Nanotech 13, 806–811 (2018).

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