Heiner Linke

From quantum-dot heat engines to hot-carrier solar cells

It has been predicted [1,2] that thermoelectric energy conversion based on ideal energy filters can, in principle, be performed near thermodynamically ideal efficiency limits, but this prediction has never been experimentally verified. Using a quantum dot (QD) embedded into a semiconductor nanowire, we directly measured the engine’s steady state electric power output. Taking into account also the calculated electronic heat flow, we find that at maximum power conditions the electronic efficiency is in agreement with the Curzon-Ahlborn efficiency, and that the overall maximum electronic efficiency is in excess of 70% of Carnot efficiency. [3] I will describe how these results may be used to enhance energy conversion efficiency also in solar cells, by harvesting non-equilibtium electronic energy based on photothermoelectric principles [4], and will show first results demonstrating a high open-circuit voltage [5].

_{[1] Mahan, G. & Sofo, J. The best thermoelectric. Proceed. Nat. Acad. Sc. 93, 7436–7439 (1996).
[2] Humphrey, T. E. Newbury, R. Taylor, R. P. & Linke, H. Reversible quantum Brownian heat engines for electrons. Phys. Rev. Lett. 89, 116801 (2002).
[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] Limpert, S. Bremner, S. & Linke, H. Reversible electron–hole separation in a hot carrier solar cell. New J. Phys. 17, 095004 (2015).
[5] Limpert, S., Burke, A., Chen, I.-J., Anttu, N., Lehmann, S., Fahlvik, S., et al. (2017). Single-nanowire, low-bandgap hot carrier solar cells with tunable open-circuit voltage. Nanotechnology, 28(43), 434001}