Seminar Erik Gauger – University of Copenhagen

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Discovery Center > Discovery calendar > Calendar 2017 > Seminar Erik Gauger

Seminar Erik Gauger

Design principles for quantum-enhanced photocells inspired by biological systems 

Abstract:
Quantum biology offers intriguing insights into the interplay of coherent quantum dynamics and strong environmental coupling.  Taking inspiration from the processes and molecular structures underlying natural photosynthesis, I will discuss design principles for biologically-inspired artificial photocells, arguing that a carefully designed interplay between dissipative and coherent dynamics may unlock non-classical performance in solar energy harvesting.

Re-emission of absorbed photons is an important factor in the Shockley Queisser limit on the efficiency of conventional photovoltaic devices. Quantum interference between two optical dipoles enables "dark-state protection", where an excitation is stored until its energy has been converted into a longer-lived form. I will show that this concept applies to wide classes of non-identical organic molecular dimers identified by high throughput screening of a quantum chemistry database [1]. Rather surprisingly, our analysis shows that these messier asymmetric dimers can even outperform the idealised case [2] under realistic constraints.

Beyond dimers, larger numbers of coherently coupled nanostructures with a highly symmetrical geometrical arrangement can unlock “superabsorption" – the inverse phenomenon to superradiance – when placed in a structured photonic environment [3]. Alternatively, considering messier ring-like systems subject to additional dissipation from a condensed matter environment leads to another effect featuring excited states that cannot decay optically but which are ready to absorb further photons. This "optical ratcheting" could serve as a buffer for a stream of incident thermal photons arriving with a random distribution of arrival times [4].

[1] Photocell optimisation using dark state protection A. Fruchtman et al, Physical Review Letters 117, 203603 (2016)

[2] Efficient Biologically Inspired Photocell Enhanced by Delocalized Quantum States C. Creatore et al, Phys. Rev. Lett. 111, 253601 (2013).

[3] Superabsorption of light via quantum engineering, K. D. B. Higgins et al, Nature Communications 5:4705 DOI: 10.1038/ncomms5705 (2014).

[4] Quantum-enhanced capture of photons using optical ratchet states, K. D. B. Higgins, B. W. Lovett, E. M. Gauger, arXiv:1504.05849.