New Publication from the SUNLAB: Applied Physics Letters

Congratulations to SUNLAB researchers, including lead author PhD candidate Gavin Forcade, and their collaborators at Princeton University and École polytechnique de Montréal, on their newest publication which was selected as Featured in Applied Physics Letters.

Waste heat is a free and abundant energy source, with 15% of global total energy use existing as waste heat above 600 K. For 600–900K temperature range, near-field thermophotovoltaics (NFTPVs) are theorized to be the most effective technology to recycle waste heat into electrical power. However, to date, experimental efficiencies have not exceeded 1.5%.

In this new work, researchers optimized the efficiency of three modeled InAs/InAsSbP-based room-temperature NFTPV devices positioned 0.1 µm from a 750 K p-doped Si radiator. They coupled a one-dimensional fluctuational electrodynamics model for the near field optics to a two-dimensional drift-diffusion model, which they validated by reproducing measured dark current–voltage curves of two previously published InAs and InAsSbP devices. The optimized devices showed four to six times higher above-bandgap energy transfer compared to the blackbody radiative limit, yielding enhanced power density, while simultaneously lowering parasitic sub-bandgap energy transfer by factors of 0.68–0.85. Substituting InAs front- and back-surface field layers with InAsSbP show 1.5- and 1.4-times higher efficiency and power output, respectively, from lowered parasitic diffusion currents. Of their three optimized designs, the best performing device has a double heterostructure with an n–i–p doping order from front to back. For radiator-thermophotovoltaic gaps of 0.01–10 µm and radiators within 600–900 K, this device has a maximum efficiency of 14.2% and a maximum power output of 1.55 W/cm2, both at 900 K. Within 600–900 K, the efficiency is always higher with near- vs far-field illumination; the team calculated up to 3.7- and 107-times higher efficiency and power output, respectively, using near-field heat transfer.

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G. P. Forcade, C. E. Valdivia, S. Molesky, S. Lu, A. W. Rodriguez, J. J. Krich, R. St-Gelais, and K. Hinzer, Efficiency-optimized near-field thermophotovoltaics using InAs and InAsSbP, Appl. Phys. Lett. 121(193903) (2022). DOI: 10.1063/5.0116806