From Quantum Dot Heat Engines to Hot-Carrier Photovoltaics

It has been known for some time that a perfect (delta-function) energy filter allows, in principle, thermal-to-electric energy conversion near ideal (Carnot) efficiency. [1,2] I will introduce this concept and report on a recent experiment where we realized a near-ideal quantum-dot heat engine in devices based on single nanowires, realizing power production at maximum power with Curzon-Ahlborn efficiency, and reaching more than 70% of Carnot efficiency at maximum efficiency settings [3].
This proof-of-performance of efficient energy harvesting from electrons is directly relevant to the concept of hot-carrier solar cells or thermophotovoltaics, where the aim is to boost energy conversion efficiency by harvesting heat from non-equilibrium electrons [4]. I will present our progress towards implementing this principle in heterostructure nanowires. [4]

References
[1] Mahan, G. D., & Sofo, J. O. (1996). The best thermoelectric. Proceedings of the National Academy of Sciences of the United States of America, 93(15), 7436–7439.
[2] Humphrey, T. E., Newbury, R., Taylor, R. P., & Linke, H. (2002). Reversible Quantum Brownian Heat Engines for Electrons. Physical Review Letters, 89(11), 116801.
[3] Martin Josefsson, Artis Svilans, Adam M. Burke, Eric A. Hoffmann, Sofia Fahlvik, Claes Thelander, Martin Leijnse, Heiner Linke: A quantum-dot heat engine operated close to thermodynamic efficiency limits. Nature Nanotechnology (2018)
[4] S. Limpert, A. Burke, I-Ju Chen, N. Anttu, S. Lehmann, S. Fahlvik S. Bremner, G. Conibeer, C. Thelander, M.E, Pistol and H. Linke: Single-nanowire, low-bandgap hot carrier solar cells with tunable open-circuit voltage Nanotechnology 28, 43 (2017)
[5] I-Ju Chen, S. Limpert, W. Metaferia, C. Thelander, L. Samuelson, F. Capasso, A.M. Burke, and H. Linke: Hot-Carrier Extraction in Nanowire-Nanoantenna Photovoltaic Devices. Nano Lett. 20, 4064 (2020)