Date and Time: 1-March-2024（Friday）10am (Beijing time)

Venue: Room 526

Speaker:  Prof. Heiner Linke, Lund University, Sweden

Host: Hongqi Xu ( Peking University / BAQIS)

Title: From quantum-dot heat engines to hot-carrier photovoltaics

About the Speaker: 

  Heiner Linke is a Professor of Nanophysics at Lund University in Sweden. Between 1998 - 2001 he was a research fellow in Sydney/Australia, before joining the physics department at the University of Oregon in 2001 where he received indefinite tenure in 2005 and remained until 2009). During 2013 - 2020 he was the Director of the Center for Nanoscience at Lund University (NanoLund), an interdisciplinary research environment engaging more than 350 scientists in three faculties. During 2021-2023 he served as the elected Deputy Dean (prorector) with responsibility for research at the Faculty of Engineering LTH (10 000 students). He has been the coordinator of five EU projects in the areas of nanoscale energy conversion and biocomputing, most lately an ERC Synergy project on artificial molecular motors (2021 – 2027). He was elected a member of the Royal Swedish Academy of Sciences (physics class) in 2014. In 2021 he was appointed to the Committee of Experts of the German Excellence Strategy.

Abstract:

  When a solar cell absorbs a photon, the resulting electron-hole pair typically has excess kinetic energy that gets lost to heat. An exciting emerging concept in photovoltaics is to use the nonequilibrium energy of such so-called “hot” charge carriers to boost solar cell efficiency or to design ultra-fast photodetectors.

  Semiconductor nanowires have several distinct advantages as a system to explore hot-carrier concepts: (i) in thin nanowires, slow carrier relaxation is observed, perhaps due to a phonon-bottleneck effect; (ii) photonic or plasmonic engineering allow to design the location of light absorption and (ii) strain relaxation enables great freedom for heterostructure band engineering for energy filtering.

  I will report on a series of experiments exploring the possibility of hot-carrier photovoltaic energy conversion in nanowires. One key element is the ability to efficiently harvest electricity from heat stored in electrons. A near-ideal quantum-dot heat engine in single, InAs/InP heterostructure nanowires, can achieve power production with Curzon-Ahlborn efficiency (> 50% of Carnot efficiency) at maximum power settings, and reaching more than 70% of Carnot efficiency at maximum efficiency settings [2].

  In experiments with light as the energy source, we demonstrated hot-carrier photothermoelectric energy conversion with an open-circuit voltage that exceeds the Shockley-Queisser limit, and we demonstrated avenues to increase quantum yield by use of plasmonic elements. [3]

  Recently, we are interested in avenues allowing us to optimize the so-called fill factor (the shape of the IV-curve) in thermal-to-electric energy conversion and found that intentional symmetry-breaking can play a perhaps unexpectedly positive role that opens up for new approaches based on fundamental symmetry considerations. [4,5] 

References

[1] Fast, J., Aeberhard, U., Bremner, S. P., & Linke, H. Hot-carrier optoelectronic devices based on semiconductor nanowires. Applied Physics Reviews, 8 (2), 021309 (2021). doi:10.1063/5.0038263

[2] 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)

[3] 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)

[4] Chen, I. J., Limpert, S., Metaferia, W., Thelander, C., Samuelson, L., Capasso, F., … Linke, H. (2020). Hot-Carrier Extraction in Nanowire-Nanoantenna Photovoltaic Devices. Nano Letters, 20(6), 4064–4072. doi:10.1021/acs.nanolett.9b04873

[5] J. Fast, H. Lundstr?m, S. Dorsch, A. Burke, P. Samuelsson, and H. Linke (2023). Geometric symmetry breaking and nonlinearity can increase thermoelectric power. arXiv:2304.01616